V4 [PATCH 2/2] ld.so: Add --list-tunables to print tunable values
Commit Message
Pass --list-tunables to ld.so to print tunables with min and max values.
---
NEWS | 2 ++
elf/Makefile | 8 ++++++++
elf/dl-main.h | 2 +-
elf/dl-tunables.c | 36 ++++++++++++++++++++++++++++++++++++
elf/dl-tunables.h | 2 ++
elf/dl-usage.c | 7 ++++++-
elf/rtld.c | 23 +++++++++++++++++++++++
manual/tunables.texi | 37 +++++++++++++++++++++++++++++++++++++
8 files changed, 115 insertions(+), 2 deletions(-)
Comments
On 31/10/2020 12:44, H.J. Lu via Libc-alpha wrote:
> Pass --list-tunables to ld.so to print tunables with min and max values.
> ---
> NEWS | 2 ++
> elf/Makefile | 8 ++++++++
> elf/dl-main.h | 2 +-
> elf/dl-tunables.c | 36 ++++++++++++++++++++++++++++++++++++
> elf/dl-tunables.h | 2 ++
> elf/dl-usage.c | 7 ++++++-
> elf/rtld.c | 23 +++++++++++++++++++++++
> manual/tunables.texi | 37 +++++++++++++++++++++++++++++++++++++
> 8 files changed, 115 insertions(+), 2 deletions(-)
>
> diff --git a/NEWS b/NEWS
> index 4307c4b1b0..a62e7307ef 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -9,6 +9,8 @@ Version 2.33
>
> Major new features:
>
> +* Pass --list-tunables to ld.so to print tunable values.
> +
Maybe use a similar sentence as for argv0:
* The dynamic linker accepts the --list-tunables argument which prints
all the supported tunables. This option is disable is glibc is
configured with tunables disabled (--enable-tunables=no).
> * The dynamic linker accepts the --argv0 argument and provides opportunity
> to change argv[0] string.
>
> diff --git a/elf/Makefile b/elf/Makefile
> index f10cc59e7c..86b282a32b 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -44,6 +44,10 @@ dl-routines += dl-tunables
> tunables-type = $(addprefix TUNABLES_FRONTEND_,$(have-tunables))
> CPPFLAGS-dl-tunables.c += -DTUNABLES_FRONTEND=$(tunables-type)
>
> +ifeq (yesyes,$(build-shared)$(run-built-tests))
> +tests-special += $(objpfx)list-tunables.out
> +endif
> +
> # Make sure that the compiler does not insert any library calls in tunables
> # code paths.
Ok, it is enabled iff 'ifneq (no,$(have-tunables))'.
> ifeq (yes,$(have-loop-to-function))
> @@ -1812,3 +1816,7 @@ $(objpfx)argv0test.out: tst-rtld-argv0.sh $(objpfx)ld.so \
> '$(test-wrapper-env)' '$(run_program_env)' \
> '$(rpath-link)' 'test-argv0' > $@; \
> $(evaluate-test)
> +
> +$(objpfx)list-tunables.out: $(objpfx)ld.so
> + $(objpfx)ld.so --list-tunables > $@; \
> + $(evaluate-test)
Maybe at least check for a tunable with a default value which be
equal to all architecture, like glibc.rtld.nns, glibc.malloc.perturb, etc?
> diff --git a/elf/dl-main.h b/elf/dl-main.h
> index b51256d3b4..f229867b8e 100644
> --- a/elf/dl-main.h
> +++ b/elf/dl-main.h
> @@ -63,7 +63,7 @@ struct audit_list
> enum rtld_mode
> {
> rtld_mode_normal, rtld_mode_list, rtld_mode_verify, rtld_mode_trace,
> - rtld_mode_help,
> + rtld_mode_list_tunables, rtld_mode_help,
> };
>
> /* Aggregated state information extracted from environment variables
Ok.
> diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
> index 2ba2844075..048601b704 100644
> --- a/elf/dl-tunables.c
> +++ b/elf/dl-tunables.c
> @@ -398,6 +398,42 @@ __tunables_init (char **envp)
> }
> }
>
> +void
> +__tunables_print (void)
> +{
> + for (int i = 0; i < sizeof (tunable_list) / sizeof (tunable_t); i++)
Use array_length here.
> + {
> + tunable_t *cur = &tunable_list[i];
Maybe use a const modifier here.
> + _dl_printf ("%s: ", cur->name);
> + switch (cur->type.type_code)
> + {
> + case TUNABLE_TYPE_INT_32:
> + _dl_printf ("%d (min: %d, max: %d)\n",
> + (int) cur->val.numval,
> + (int) cur->type.min,
> + (int) cur->type.max);
> + break;
> + case TUNABLE_TYPE_UINT_64:
> + _dl_printf ("0x%lx (min: 0x%lx, max: 0x%lx)\n",
> + (long int) cur->val.numval,
> + (long int) cur->type.min,
> + (long int) cur->type.max);
> + break;
> + case TUNABLE_TYPE_SIZE_T:
> + _dl_printf ("0x%Zx (min: 0x%Zx, max: 0x%Zx)\n",
> + (size_t) cur->val.numval,
> + (size_t) cur->type.min,
> + (size_t) cur->type.max);
> + break;
> + case TUNABLE_TYPE_STRING:
> + _dl_printf ("%s\n", cur->val.strval ? cur->val.strval : "");
> + break;
> + default:
> + __builtin_unreachable ();
> + }
> + }
> +}
> +
Ok, it should be ok to use '%d' for signed and 'lx' for unsigned.
> /* Set the tunable value. This is called by the module that the tunable exists
> in. */
> void
> diff --git a/elf/dl-tunables.h b/elf/dl-tunables.h
> index 550b0cc7f4..4a0c90f3e0 100644
> --- a/elf/dl-tunables.h
> +++ b/elf/dl-tunables.h
> @@ -69,9 +69,11 @@ typedef struct _tunable tunable_t;
> # include "dl-tunable-list.h"
>
> extern void __tunables_init (char **);
> +extern void __tunables_print (void);
> extern void __tunable_get_val (tunable_id_t, void *, tunable_callback_t);
> extern void __tunable_set_val (tunable_id_t, void *, void *, void *);
> rtld_hidden_proto (__tunables_init)
> +rtld_hidden_proto (__tunables_print)
> rtld_hidden_proto (__tunable_get_val)
> rtld_hidden_proto (__tunable_set_val)
>
Ok.
> diff --git a/elf/dl-usage.c b/elf/dl-usage.c
> index 796ad38b43..3ce19fb892 100644
> --- a/elf/dl-usage.c
> +++ b/elf/dl-usage.c
> @@ -190,7 +190,12 @@ setting environment variables (which would be inherited by subprocesses).\n\
> in LIST\n\
> --audit LIST use objects named in LIST as auditors\n\
> --preload LIST preload objects named in LIST\n\
> - --argv0 STRING set argv[0] to STRING before running\n\
> + --argv0 STRING set argv[0] to STRING before running\n"
> +#if HAVE_TUNABLES
> +"\
> + --list-tunables list all tunables with minimum and maximum values\n"
> +#endif
> +"\
> --help display this help and exit\n\
> --version output version information and exit\n\
> \n\
Ok.
> diff --git a/elf/rtld.c b/elf/rtld.c
> index 5d117d0d2c..33993a6f8b 100644
> --- a/elf/rtld.c
> +++ b/elf/rtld.c
> @@ -49,6 +49,10 @@
> #include <libc-early-init.h>
> #include <dl-main.h>
>
> +#if HAVE_TUNABLES
> +# include <dl-tunables.h>
> +#endif
> +
You can include this header regadless of HAVE_TUNABLES (it handles it
internally).
> #include <assert.h>
>
> /* Only enables rtld profiling for architectures which provides non generic
> @@ -1248,6 +1252,16 @@ dl_main (const ElfW(Phdr) *phdr,
> _dl_argc -= 2;
> _dl_argv += 2;
> }
> +#if HAVE_TUNABLES
> + else if (! strcmp (_dl_argv[1], "--list-tunables"))
> + {
> + state.mode = rtld_mode_list_tunables;
> +
> + ++_dl_skip_args;
> + --_dl_argc;
> + ++_dl_argv;
> + }
> +#endif
> else if (strcmp (_dl_argv[1], "--help") == 0)
> {
> state.mode = rtld_mode_help;
> @@ -1268,6 +1282,15 @@ dl_main (const ElfW(Phdr) *phdr,
> else
> break;
>
> +#if HAVE_TUNABLES
> + if (__builtin_expect (state.mode, rtld_mode_normal)
> + == rtld_mode_list_tunables)
Use
if (__glibc_unlikely (state.mode == rtld_mode_list_tunables)
> + {
> + __tunables_print ();
> + _exit (0);
> + }
> +#endif
> +
> /* If we have no further argument the program was called incorrectly.
> Grant the user some education. */
> if (_dl_argc < 2)
> diff --git a/manual/tunables.texi b/manual/tunables.texi
> index d72d7a5ec0..924dac8876 100644
> --- a/manual/tunables.texi
> +++ b/manual/tunables.texi
> @@ -28,6 +28,43 @@ Finally, the set of tunables available may vary between distributions as
> the tunables feature allows distributions to add their own tunables under
> their own namespace.
>
> +Passing @option{--list-tunables} to the dynamic loader to print all
> +tunables with minimum and maximum values:
> +
> +@example
> +$ /lib64/ld-linux-x86-64.so.2 --list-tunables
> +glibc.rtld.nns: 0x4 (min: 0x1, max: 0x10)
> +glibc.elision.skip_lock_after_retries: 3 (min: -2147483648, max: 2147483647)
> +glibc.malloc.trim_threshold: 0x0 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.malloc.perturb: 0 (min: 0, max: 255)
> +glibc.cpu.x86_shared_cache_size: 0x100000 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.elision.tries: 3 (min: -2147483648, max: 2147483647)
> +glibc.elision.enable: 0 (min: 0, max: 1)
> +glibc.cpu.x86_rep_movsb_threshold: 0x800 (min: 0x100, max: 0xffffffffffffffff)
> +glibc.malloc.mxfast: 0x0 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.elision.skip_lock_busy: 3 (min: -2147483648, max: 2147483647)
> +glibc.malloc.top_pad: 0x0 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.cpu.x86_rep_stosb_threshold: 0x800 (min: 0x1, max: 0xffffffffffffffff)
> +glibc.cpu.x86_non_temporal_threshold: 0xc0000 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.cpu.x86_shstk:
Trailing whitespace.
> +glibc.cpu.hwcap_mask: 0x6 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.malloc.mmap_max: 0 (min: -2147483648, max: 2147483647)
> +glibc.elision.skip_trylock_internal_abort: 3 (min: -2147483648, max: 2147483647)
> +glibc.malloc.tcache_unsorted_limit: 0x0 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.cpu.x86_ibt:
Ditto.
> +glibc.cpu.hwcaps:
Ditto.
> +glibc.elision.skip_lock_internal_abort: 3 (min: -2147483648, max: 2147483647)
> +glibc.malloc.arena_max: 0x0 (min: 0x1, max: 0xffffffffffffffff)
> +glibc.malloc.mmap_threshold: 0x0 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.cpu.x86_data_cache_size: 0x8000 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.malloc.tcache_count: 0x0 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.malloc.arena_test: 0x0 (min: 0x1, max: 0xffffffffffffffff)
> +glibc.pthread.mutex_spin_count: 100 (min: 0, max: 32767)
> +glibc.rtld.optional_static_tls: 0x200 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.malloc.tcache_max: 0x0 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.malloc.check: 0 (min: 0, max: 3)
> +@end example
> +
> @menu
> * Tunable names:: The structure of a tunable name
> * Memory Allocation Tunables:: Tunables in the memory allocation subsystem
>
On Thu, Jan 14, 2021 at 10:35 AM Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
>
>
>
> On 31/10/2020 12:44, H.J. Lu via Libc-alpha wrote:
> > Pass --list-tunables to ld.so to print tunables with min and max values.
> > ---
> > NEWS | 2 ++
> > elf/Makefile | 8 ++++++++
> > elf/dl-main.h | 2 +-
> > elf/dl-tunables.c | 36 ++++++++++++++++++++++++++++++++++++
> > elf/dl-tunables.h | 2 ++
> > elf/dl-usage.c | 7 ++++++-
> > elf/rtld.c | 23 +++++++++++++++++++++++
> > manual/tunables.texi | 37 +++++++++++++++++++++++++++++++++++++
> > 8 files changed, 115 insertions(+), 2 deletions(-)
> >
> > diff --git a/NEWS b/NEWS
> > index 4307c4b1b0..a62e7307ef 100644
> > --- a/NEWS
> > +++ b/NEWS
> > @@ -9,6 +9,8 @@ Version 2.33
> >
> > Major new features:
> >
> > +* Pass --list-tunables to ld.so to print tunable values.
> > +
>
> Maybe use a similar sentence as for argv0:
>
> * The dynamic linker accepts the --list-tunables argument which prints
> all the supported tunables. This option is disable is glibc is
> configured with tunables disabled (--enable-tunables=no).
Fixed.
> > * The dynamic linker accepts the --argv0 argument and provides opportunity
> > to change argv[0] string.
> >
> > diff --git a/elf/Makefile b/elf/Makefile
> > index f10cc59e7c..86b282a32b 100644
> > --- a/elf/Makefile
> > +++ b/elf/Makefile
> > @@ -44,6 +44,10 @@ dl-routines += dl-tunables
> > tunables-type = $(addprefix TUNABLES_FRONTEND_,$(have-tunables))
> > CPPFLAGS-dl-tunables.c += -DTUNABLES_FRONTEND=$(tunables-type)
> >
> > +ifeq (yesyes,$(build-shared)$(run-built-tests))
> > +tests-special += $(objpfx)list-tunables.out
> > +endif
> > +
> > # Make sure that the compiler does not insert any library calls in tunables
> > # code paths.
>
> Ok, it is enabled iff 'ifneq (no,$(have-tunables))'.
>
> > ifeq (yes,$(have-loop-to-function))
> > @@ -1812,3 +1816,7 @@ $(objpfx)argv0test.out: tst-rtld-argv0.sh $(objpfx)ld.so \
> > '$(test-wrapper-env)' '$(run_program_env)' \
> > '$(rpath-link)' 'test-argv0' > $@; \
> > $(evaluate-test)
> > +
> > +$(objpfx)list-tunables.out: $(objpfx)ld.so
> > + $(objpfx)ld.so --list-tunables > $@; \
> > + $(evaluate-test)
>
> Maybe at least check for a tunable with a default value which be
> equal to all architecture, like glibc.rtld.nns, glibc.malloc.perturb, etc?
I added elf/tst-rtld-list-tunables.exp and elf/tst-rtld-list-tunables.sh
to compare against rtld and malloc tunables. It passed on i686, x32
and x86-64.
> > diff --git a/elf/dl-main.h b/elf/dl-main.h
> > index b51256d3b4..f229867b8e 100644
> > --- a/elf/dl-main.h
> > +++ b/elf/dl-main.h
> > @@ -63,7 +63,7 @@ struct audit_list
> > enum rtld_mode
> > {
> > rtld_mode_normal, rtld_mode_list, rtld_mode_verify, rtld_mode_trace,
> > - rtld_mode_help,
> > + rtld_mode_list_tunables, rtld_mode_help,
> > };
> >
> > /* Aggregated state information extracted from environment variables
>
> Ok.
>
> > diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
> > index 2ba2844075..048601b704 100644
> > --- a/elf/dl-tunables.c
> > +++ b/elf/dl-tunables.c
> > @@ -398,6 +398,42 @@ __tunables_init (char **envp)
> > }
> > }
> >
> > +void
> > +__tunables_print (void)
> > +{
> > + for (int i = 0; i < sizeof (tunable_list) / sizeof (tunable_t); i++)
>
> Use array_length here.
Fixed.
> > + {
> > + tunable_t *cur = &tunable_list[i];
>
> Maybe use a const modifier here.
Fixed.
> > + _dl_printf ("%s: ", cur->name);
> > + switch (cur->type.type_code)
> > + {
> > + case TUNABLE_TYPE_INT_32:
> > + _dl_printf ("%d (min: %d, max: %d)\n",
> > + (int) cur->val.numval,
> > + (int) cur->type.min,
> > + (int) cur->type.max);
> > + break;
> > + case TUNABLE_TYPE_UINT_64:
> > + _dl_printf ("0x%lx (min: 0x%lx, max: 0x%lx)\n",
> > + (long int) cur->val.numval,
> > + (long int) cur->type.min,
> > + (long int) cur->type.max);
> > + break;
> > + case TUNABLE_TYPE_SIZE_T:
> > + _dl_printf ("0x%Zx (min: 0x%Zx, max: 0x%Zx)\n",
> > + (size_t) cur->val.numval,
> > + (size_t) cur->type.min,
> > + (size_t) cur->type.max);
> > + break;
> > + case TUNABLE_TYPE_STRING:
> > + _dl_printf ("%s\n", cur->val.strval ? cur->val.strval : "");
> > + break;
> > + default:
> > + __builtin_unreachable ();
> > + }
> > + }
> > +}
> > +
>
> Ok, it should be ok to use '%d' for signed and 'lx' for unsigned.
>
> > /* Set the tunable value. This is called by the module that the tunable exists
> > in. */
> > void
> > diff --git a/elf/dl-tunables.h b/elf/dl-tunables.h
> > index 550b0cc7f4..4a0c90f3e0 100644
> > --- a/elf/dl-tunables.h
> > +++ b/elf/dl-tunables.h
> > @@ -69,9 +69,11 @@ typedef struct _tunable tunable_t;
> > # include "dl-tunable-list.h"
> >
> > extern void __tunables_init (char **);
> > +extern void __tunables_print (void);
> > extern void __tunable_get_val (tunable_id_t, void *, tunable_callback_t);
> > extern void __tunable_set_val (tunable_id_t, void *, void *, void *);
> > rtld_hidden_proto (__tunables_init)
> > +rtld_hidden_proto (__tunables_print)
> > rtld_hidden_proto (__tunable_get_val)
> > rtld_hidden_proto (__tunable_set_val)
> >
>
> Ok.
>
> > diff --git a/elf/dl-usage.c b/elf/dl-usage.c
> > index 796ad38b43..3ce19fb892 100644
> > --- a/elf/dl-usage.c
> > +++ b/elf/dl-usage.c
> > @@ -190,7 +190,12 @@ setting environment variables (which would be inherited by subprocesses).\n\
> > in LIST\n\
> > --audit LIST use objects named in LIST as auditors\n\
> > --preload LIST preload objects named in LIST\n\
> > - --argv0 STRING set argv[0] to STRING before running\n\
> > + --argv0 STRING set argv[0] to STRING before running\n"
> > +#if HAVE_TUNABLES
> > +"\
> > + --list-tunables list all tunables with minimum and maximum values\n"
> > +#endif
> > +"\
> > --help display this help and exit\n\
> > --version output version information and exit\n\
> > \n\
>
> Ok.
>
> > diff --git a/elf/rtld.c b/elf/rtld.c
> > index 5d117d0d2c..33993a6f8b 100644
> > --- a/elf/rtld.c
> > +++ b/elf/rtld.c
> > @@ -49,6 +49,10 @@
> > #include <libc-early-init.h>
> > #include <dl-main.h>
> >
> > +#if HAVE_TUNABLES
> > +# include <dl-tunables.h>
> > +#endif
> > +
>
> You can include this header regadless of HAVE_TUNABLES (it handles it
> internally).
Fixed.
> > #include <assert.h>
> >
> > /* Only enables rtld profiling for architectures which provides non generic
> > @@ -1248,6 +1252,16 @@ dl_main (const ElfW(Phdr) *phdr,
> > _dl_argc -= 2;
> > _dl_argv += 2;
> > }
> > +#if HAVE_TUNABLES
> > + else if (! strcmp (_dl_argv[1], "--list-tunables"))
> > + {
> > + state.mode = rtld_mode_list_tunables;
> > +
> > + ++_dl_skip_args;
> > + --_dl_argc;
> > + ++_dl_argv;
> > + }
> > +#endif
> > else if (strcmp (_dl_argv[1], "--help") == 0)
> > {
> > state.mode = rtld_mode_help;
> > @@ -1268,6 +1282,15 @@ dl_main (const ElfW(Phdr) *phdr,
> > else
> > break;
> >
> > +#if HAVE_TUNABLES
> > + if (__builtin_expect (state.mode, rtld_mode_normal)
> > + == rtld_mode_list_tunables)
>
> Use
>
> if (__glibc_unlikely (state.mode == rtld_mode_list_tunables)
Fixed.
> > + {
> > + __tunables_print ();
> > + _exit (0);
> > + }
> > +#endif
> > +
> > /* If we have no further argument the program was called incorrectly.
> > Grant the user some education. */
> > if (_dl_argc < 2)
> > diff --git a/manual/tunables.texi b/manual/tunables.texi
> > index d72d7a5ec0..924dac8876 100644
> > --- a/manual/tunables.texi
> > +++ b/manual/tunables.texi
> > @@ -28,6 +28,43 @@ Finally, the set of tunables available may vary between distributions as
> > the tunables feature allows distributions to add their own tunables under
> > their own namespace.
> >
> > +Passing @option{--list-tunables} to the dynamic loader to print all
> > +tunables with minimum and maximum values:
> > +
> > +@example
> > +$ /lib64/ld-linux-x86-64.so.2 --list-tunables
> > +glibc.rtld.nns: 0x4 (min: 0x1, max: 0x10)
> > +glibc.elision.skip_lock_after_retries: 3 (min: -2147483648, max: 2147483647)
> > +glibc.malloc.trim_threshold: 0x0 (min: 0x0, max: 0xffffffffffffffff)
> > +glibc.malloc.perturb: 0 (min: 0, max: 255)
> > +glibc.cpu.x86_shared_cache_size: 0x100000 (min: 0x0, max: 0xffffffffffffffff)
> > +glibc.elision.tries: 3 (min: -2147483648, max: 2147483647)
> > +glibc.elision.enable: 0 (min: 0, max: 1)
> > +glibc.cpu.x86_rep_movsb_threshold: 0x800 (min: 0x100, max: 0xffffffffffffffff)
> > +glibc.malloc.mxfast: 0x0 (min: 0x0, max: 0xffffffffffffffff)
> > +glibc.elision.skip_lock_busy: 3 (min: -2147483648, max: 2147483647)
> > +glibc.malloc.top_pad: 0x0 (min: 0x0, max: 0xffffffffffffffff)
> > +glibc.cpu.x86_rep_stosb_threshold: 0x800 (min: 0x1, max: 0xffffffffffffffff)
> > +glibc.cpu.x86_non_temporal_threshold: 0xc0000 (min: 0x0, max: 0xffffffffffffffff)
> > +glibc.cpu.x86_shstk:
>
> Trailing whitespace.
Fixed.
> > +glibc.cpu.hwcap_mask: 0x6 (min: 0x0, max: 0xffffffffffffffff)
> > +glibc.malloc.mmap_max: 0 (min: -2147483648, max: 2147483647)
> > +glibc.elision.skip_trylock_internal_abort: 3 (min: -2147483648, max: 2147483647)
> > +glibc.malloc.tcache_unsorted_limit: 0x0 (min: 0x0, max: 0xffffffffffffffff)
> > +glibc.cpu.x86_ibt:
>
> Ditto.
Fixed.
> > +glibc.cpu.hwcaps:
>
> Ditto.
Fixed.
> > +glibc.elision.skip_lock_internal_abort: 3 (min: -2147483648, max: 2147483647)
> > +glibc.malloc.arena_max: 0x0 (min: 0x1, max: 0xffffffffffffffff)
> > +glibc.malloc.mmap_threshold: 0x0 (min: 0x0, max: 0xffffffffffffffff)
> > +glibc.cpu.x86_data_cache_size: 0x8000 (min: 0x0, max: 0xffffffffffffffff)
> > +glibc.malloc.tcache_count: 0x0 (min: 0x0, max: 0xffffffffffffffff)
> > +glibc.malloc.arena_test: 0x0 (min: 0x1, max: 0xffffffffffffffff)
> > +glibc.pthread.mutex_spin_count: 100 (min: 0, max: 32767)
> > +glibc.rtld.optional_static_tls: 0x200 (min: 0x0, max: 0xffffffffffffffff)
> > +glibc.malloc.tcache_max: 0x0 (min: 0x0, max: 0xffffffffffffffff)
> > +glibc.malloc.check: 0 (min: 0, max: 3)
> > +@end example
> > +
> > @menu
> > * Tunable names:: The structure of a tunable name
> > * Memory Allocation Tunables:: Tunables in the memory allocation subsystem
> >
Here is the updated patch. OK for master?
Thanks.
On 14/01/2021 19:25, H.J. Lu wrote:
> On Thu, Jan 14, 2021 at 10:35 AM Adhemerval Zanella
> <adhemerval.zanella@linaro.org> wrote:
>>
>>
>>
>> On 31/10/2020 12:44, H.J. Lu via Libc-alpha wrote:
>
> Here is the updated patch. OK for master?
>
> Thanks.
LGTM, thanks.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
>
> From 2745fc527295ad735d14bdaf6052c40dc24772a8 Mon Sep 17 00:00:00 2001
> From: "H.J. Lu" <hjl.tools@gmail.com>
> Date: Sun, 12 Jul 2020 06:04:53 -0700
> Subject: [PATCH] ld.so: Add --list-tunables to print tunable values
>
> Pass --list-tunables to ld.so to print tunables with min and max values.
> ---
> NEWS | 4 ++++
> elf/Makefile | 13 ++++++++++
> elf/dl-main.h | 2 +-
> elf/dl-tunables.c | 43 ++++++++++++++++++++++++++++++++++
> elf/dl-tunables.h | 2 ++
> elf/dl-usage.c | 7 +++++-
> elf/rtld.c | 19 +++++++++++++++
> elf/tst-rtld-list-tunables.exp | 14 +++++++++++
> elf/tst-rtld-list-tunables.sh | 34 +++++++++++++++++++++++++++
> manual/tunables.texi | 38 ++++++++++++++++++++++++++++++
> 10 files changed, 174 insertions(+), 2 deletions(-)
> create mode 100644 elf/tst-rtld-list-tunables.exp
> create mode 100755 elf/tst-rtld-list-tunables.sh
>
> diff --git a/NEWS b/NEWS
> index face78cd10..d121f7df87 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -9,6 +9,10 @@ Version 2.33
>
> Major new features:
>
> +* The dynamic linker accepts the --list-tunables argument which prints
> + all the supported tunables. This option is disable if glibc is
> + configured with tunables disabled (--enable-tunables=no).
> +
> * The dynamic linker accepts the --argv0 argument and provides opportunity
> to change argv[0] string.
>
Ok.
> diff --git a/elf/Makefile b/elf/Makefile
> index c41d11693b..0e46cab699 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -45,6 +45,10 @@ dl-routines += dl-tunables
> tunables-type = $(addprefix TUNABLES_FRONTEND_,$(have-tunables))
> CPPFLAGS-dl-tunables.c += -DTUNABLES_FRONTEND=$(tunables-type)
>
> +ifeq (yesyes,$(build-shared)$(run-built-tests))
> +tests-special += $(objpfx)list-tunables.out
> +endif
> +
> # Make sure that the compiler does not insert any library calls in tunables
> # code paths.
> ifeq (yes,$(have-loop-to-function))
Ok.
> @@ -1896,3 +1900,12 @@ $(objpfx)tst-glibc-hwcaps-mask.out: \
> # Generic dependency for sysdeps implementation of
> # tst-glibc-hwcaps-cache.
> $(objpfx)tst-glibc-hwcaps-cache.out: $(objpfx)tst-glibc-hwcaps
> +
> +$(objpfx)list-tunables.out: tst-rtld-list-tunables.sh $(objpfx)ld.so
> + $(objpfx)ld.so --list-tunables > $@; \
> + $(evaluate-test)
> + $(SHELL) $< $(objpfx)ld.so '$(test-wrapper-env)' \
> + '$(run_program_env)' > $(objpfx)/tst-rtld-list-tunables.out
> + cmp tst-rtld-list-tunables.exp \
> + $(objpfx)/tst-rtld-list-tunables.out > $@; \
> + $(evaluate-test)
Ok.
> diff --git a/elf/dl-main.h b/elf/dl-main.h
> index 0bccab165f..3a5e13c739 100644
> --- a/elf/dl-main.h
> +++ b/elf/dl-main.h
> @@ -63,7 +63,7 @@ struct audit_list
> enum rtld_mode
> {
> rtld_mode_normal, rtld_mode_list, rtld_mode_verify, rtld_mode_trace,
> - rtld_mode_help,
> + rtld_mode_list_tunables, rtld_mode_help,
> };
>
> /* Aggregated state information extracted from environment variables
Ok.
> diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
> index 9b4d737fb8..33be00e447 100644
> --- a/elf/dl-tunables.c
> +++ b/elf/dl-tunables.c
> @@ -26,6 +26,7 @@
> #include <sysdep.h>
> #include <fcntl.h>
> #include <ldsodefs.h>
> +#include <array_length.h>
>
> #define TUNABLES_INTERNAL 1
> #include "dl-tunables.h"
> @@ -398,6 +399,48 @@ __tunables_init (char **envp)
> }
> }
>
> +void
> +__tunables_print (void)
> +{
> + for (int i = 0; i < array_length (tunable_list); i++)
> + {
> + const tunable_t *cur = &tunable_list[i];
> + if (cur->type.type_code == TUNABLE_TYPE_STRING
> + && cur->val.strval == NULL)
> + _dl_printf ("%s:\n", cur->name);
> + else
> + {
> + _dl_printf ("%s: ", cur->name);
> + switch (cur->type.type_code)
> + {
> + case TUNABLE_TYPE_INT_32:
> + _dl_printf ("%d (min: %d, max: %d)\n",
> + (int) cur->val.numval,
> + (int) cur->type.min,
> + (int) cur->type.max);
> + break;
> + case TUNABLE_TYPE_UINT_64:
> + _dl_printf ("0x%lx (min: 0x%lx, max: 0x%lx)\n",
> + (long int) cur->val.numval,
> + (long int) cur->type.min,
> + (long int) cur->type.max);
> + break;
> + case TUNABLE_TYPE_SIZE_T:
> + _dl_printf ("0x%Zx (min: 0x%Zx, max: 0x%Zx)\n",
> + (size_t) cur->val.numval,
> + (size_t) cur->type.min,
> + (size_t) cur->type.max);
> + break;
> + case TUNABLE_TYPE_STRING:
> + _dl_printf ("%s\n", cur->val.strval);
> + break;
> + default:
> + __builtin_unreachable ();
> + }
> + }
> + }
> +}
> +
> /* Set the tunable value. This is called by the module that the tunable exists
> in. */
> void
Ok.
> diff --git a/elf/dl-tunables.h b/elf/dl-tunables.h
> index 518342a300..dfa16c1977 100644
> --- a/elf/dl-tunables.h
> +++ b/elf/dl-tunables.h
> @@ -69,9 +69,11 @@ typedef struct _tunable tunable_t;
> # include "dl-tunable-list.h"
>
> extern void __tunables_init (char **);
> +extern void __tunables_print (void);
> extern void __tunable_get_val (tunable_id_t, void *, tunable_callback_t);
> extern void __tunable_set_val (tunable_id_t, void *, void *, void *);
> rtld_hidden_proto (__tunables_init)
> +rtld_hidden_proto (__tunables_print)
> rtld_hidden_proto (__tunable_get_val)
> rtld_hidden_proto (__tunable_set_val)
>
Ok.
> diff --git a/elf/dl-usage.c b/elf/dl-usage.c
> index 907f068cfb..6e26818bd7 100644
> --- a/elf/dl-usage.c
> +++ b/elf/dl-usage.c
> @@ -255,7 +255,12 @@ setting environment variables (which would be inherited by subprocesses).\n\
> in LIST\n\
> --audit LIST use objects named in LIST as auditors\n\
> --preload LIST preload objects named in LIST\n\
> - --argv0 STRING set argv[0] to STRING before running\n\
> + --argv0 STRING set argv[0] to STRING before running\n"
> +#if HAVE_TUNABLES
> +"\
> + --list-tunables list all tunables with minimum and maximum values\n"
> +#endif
> +"\
> --help display this help and exit\n\
> --version output version information and exit\n\
> \n\
Ok.
> diff --git a/elf/rtld.c b/elf/rtld.c
> index 8d9add90e3..596b6ac3d9 100644
> --- a/elf/rtld.c
> +++ b/elf/rtld.c
> @@ -50,6 +50,7 @@
> #include <dl-main.h>
> #include <list.h>
> #include <gnu/lib-names.h>
> +#include <dl-tunables.h>
>
> #include <assert.h>
>
> @@ -1276,6 +1277,16 @@ dl_main (const ElfW(Phdr) *phdr,
> _dl_argc -= 2;
> _dl_argv += 2;
> }
> +#if HAVE_TUNABLES
> + else if (! strcmp (_dl_argv[1], "--list-tunables"))
> + {
> + state.mode = rtld_mode_list_tunables;
> +
> + ++_dl_skip_args;
> + --_dl_argc;
> + ++_dl_argv;
> + }
> +#endif
> else if (strcmp (_dl_argv[1], "--help") == 0)
> {
> state.mode = rtld_mode_help;
> @@ -1296,6 +1307,14 @@ dl_main (const ElfW(Phdr) *phdr,
> else
> break;
>
> +#if HAVE_TUNABLES
> + if (__glibc_unlikely (state.mode == rtld_mode_list_tunables))
> + {
> + __tunables_print ();
> + _exit (0);
> + }
> +#endif
> +
> /* If we have no further argument the program was called incorrectly.
> Grant the user some education. */
> if (_dl_argc < 2)
Ok.
> diff --git a/elf/tst-rtld-list-tunables.exp b/elf/tst-rtld-list-tunables.exp
> new file mode 100644
> index 0000000000..4f3f7ee4e3
> --- /dev/null
> +++ b/elf/tst-rtld-list-tunables.exp
> @@ -0,0 +1,14 @@
> +glibc.malloc.arena_max: 0x0 (min: 0x1, max: 0x[f]+)
> +glibc.malloc.arena_test: 0x0 (min: 0x1, max: 0x[f]+)
> +glibc.malloc.check: 0 (min: 0, max: 3)
> +glibc.malloc.mmap_max: 0 (min: -2147483648, max: 2147483647)
> +glibc.malloc.mmap_threshold: 0x0 (min: 0x0, max: 0x[f]+)
> +glibc.malloc.mxfast: 0x0 (min: 0x0, max: 0x[f]+)
> +glibc.malloc.perturb: 0 (min: 0, max: 255)
> +glibc.malloc.tcache_count: 0x0 (min: 0x0, max: 0x[f]+)
> +glibc.malloc.tcache_max: 0x0 (min: 0x0, max: 0x[f]+)
> +glibc.malloc.tcache_unsorted_limit: 0x0 (min: 0x0, max: 0x[f]+)
> +glibc.malloc.top_pad: 0x0 (min: 0x0, max: 0x[f]+)
> +glibc.malloc.trim_threshold: 0x0 (min: 0x0, max: 0x[f]+)
> +glibc.rtld.nns: 0x4 (min: 0x1, max: 0x10)
> +glibc.rtld.optional_static_tls: 0x200 (min: 0x0, max: 0x[f]+)
Ok, it seems to be to common ones.
> diff --git a/elf/tst-rtld-list-tunables.sh b/elf/tst-rtld-list-tunables.sh
> new file mode 100755
> index 0000000000..e7bbdde949
> --- /dev/null
> +++ b/elf/tst-rtld-list-tunables.sh
> @@ -0,0 +1,34 @@
> +#!/bin/sh
> +# Test for --list-tunables option ld.so.
> +# Copyright (C) 2021 Free Software Foundation, Inc.
> +# This file is part of the GNU C Library.
> +#
> +# The GNU C Library is free software; you can redistribute it and/or
> +# modify it under the terms of the GNU Lesser General Public
> +# License as published by the Free Software Foundation; either
> +# version 2.1 of the License, or (at your option) any later version.
> +#
> +# The GNU C Library is distributed in the hope that it will be useful,
> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> +# Lesser General Public License for more details.
> +#
> +# You should have received a copy of the GNU Lesser General Public
> +# License along with the GNU C Library; if not, see
> +# <https://www.gnu.org/licenses/>.
> +
> +set -e
> +
> +rtld=$1
> +test_wrapper_env=$2
> +run_program_env=$3
> +
> +LC_ALL=C
> +export LC_ALL
> +
> +${test_wrapper_env} \
> +${run_program_env} \
> +$rtld --list-tunables \
> +| sort -u \
> +| egrep "(rtld|malloc)" \
> +| sed -e "s/0xf\+/0x[f]+/"
Ok.
> diff --git a/manual/tunables.texi b/manual/tunables.texi
> index 1bbdc88281..1b746c0fa1 100644
> --- a/manual/tunables.texi
> +++ b/manual/tunables.texi
> @@ -28,6 +28,44 @@ Finally, the set of tunables available may vary between distributions as
> the tunables feature allows distributions to add their own tunables under
> their own namespace.
>
> +Passing @option{--list-tunables} to the dynamic loader to print all
> +tunables with minimum and maximum values:
> +
> +@example
> +$ /lib64/ld-linux-x86-64.so.2 --list-tunables
> +glibc.rtld.nns: 0x4 (min: 0x1, max: 0x10)
> +glibc.elision.skip_lock_after_retries: 3 (min: -2147483648, max: 2147483647)
> +glibc.malloc.trim_threshold: 0x0 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.malloc.perturb: 0 (min: 0, max: 255)
> +glibc.cpu.x86_shared_cache_size: 0x100000 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.mem.tagging: 0 (min: 0, max: 255)
> +glibc.elision.tries: 3 (min: -2147483648, max: 2147483647)
> +glibc.elision.enable: 0 (min: 0, max: 1)
> +glibc.cpu.x86_rep_movsb_threshold: 0x1000 (min: 0x100, max: 0xffffffffffffffff)
> +glibc.malloc.mxfast: 0x0 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.elision.skip_lock_busy: 3 (min: -2147483648, max: 2147483647)
> +glibc.malloc.top_pad: 0x0 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.cpu.x86_rep_stosb_threshold: 0x800 (min: 0x1, max: 0xffffffffffffffff)
> +glibc.cpu.x86_non_temporal_threshold: 0xc0000 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.cpu.x86_shstk:
> +glibc.cpu.hwcap_mask: 0x6 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.malloc.mmap_max: 0 (min: -2147483648, max: 2147483647)
> +glibc.elision.skip_trylock_internal_abort: 3 (min: -2147483648, max: 2147483647)
> +glibc.malloc.tcache_unsorted_limit: 0x0 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.cpu.x86_ibt:
> +glibc.cpu.hwcaps:
> +glibc.elision.skip_lock_internal_abort: 3 (min: -2147483648, max: 2147483647)
> +glibc.malloc.arena_max: 0x0 (min: 0x1, max: 0xffffffffffffffff)
> +glibc.malloc.mmap_threshold: 0x0 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.cpu.x86_data_cache_size: 0x8000 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.malloc.tcache_count: 0x0 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.malloc.arena_test: 0x0 (min: 0x1, max: 0xffffffffffffffff)
> +glibc.pthread.mutex_spin_count: 100 (min: 0, max: 32767)
> +glibc.rtld.optional_static_tls: 0x200 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.malloc.tcache_max: 0x0 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.malloc.check: 0 (min: 0, max: 3)
> +@end example
> +
> @menu
> * Tunable names:: The structure of a tunable name
> * Memory Allocation Tunables:: Tunables in the memory allocation subsystem
> --
> 2.29.2
On Jan 14 2021, H.J. Lu via Libc-alpha wrote:
> diff --git a/elf/tst-rtld-list-tunables.exp b/elf/tst-rtld-list-tunables.exp
> new file mode 100644
> index 0000000000..4f3f7ee4e3
> --- /dev/null
> +++ b/elf/tst-rtld-list-tunables.exp
> @@ -0,0 +1,14 @@
> +glibc.malloc.arena_max: 0x0 (min: 0x1, max: 0x[f]+)
> +glibc.malloc.arena_test: 0x0 (min: 0x1, max: 0x[f]+)
> +glibc.malloc.check: 0 (min: 0, max: 3)
> +glibc.malloc.mmap_max: 0 (min: -2147483648, max: 2147483647)
> +glibc.malloc.mmap_threshold: 0x0 (min: 0x0, max: 0x[f]+)
> +glibc.malloc.mxfast: 0x0 (min: 0x0, max: 0x[f]+)
> +glibc.malloc.perturb: 0 (min: 0, max: 255)
> +glibc.malloc.tcache_count: 0x0 (min: 0x0, max: 0x[f]+)
> +glibc.malloc.tcache_max: 0x0 (min: 0x0, max: 0x[f]+)
> +glibc.malloc.tcache_unsorted_limit: 0x0 (min: 0x0, max: 0x[f]+)
> +glibc.malloc.top_pad: 0x0 (min: 0x0, max: 0x[f]+)
> +glibc.malloc.trim_threshold: 0x0 (min: 0x0, max: 0x[f]+)
> +glibc.rtld.nns: 0x4 (min: 0x1, max: 0x10)
> +glibc.rtld.optional_static_tls: 0x200 (min: 0x0, max: 0x[f]+)
This won't match if MALLOC_PERTURB_ is set.
Andreas.
@@ -9,6 +9,8 @@ Version 2.33
Major new features:
+* Pass --list-tunables to ld.so to print tunable values.
+
* The dynamic linker accepts the --argv0 argument and provides opportunity
to change argv[0] string.
@@ -44,6 +44,10 @@ dl-routines += dl-tunables
tunables-type = $(addprefix TUNABLES_FRONTEND_,$(have-tunables))
CPPFLAGS-dl-tunables.c += -DTUNABLES_FRONTEND=$(tunables-type)
+ifeq (yesyes,$(build-shared)$(run-built-tests))
+tests-special += $(objpfx)list-tunables.out
+endif
+
# Make sure that the compiler does not insert any library calls in tunables
# code paths.
ifeq (yes,$(have-loop-to-function))
@@ -1812,3 +1816,7 @@ $(objpfx)argv0test.out: tst-rtld-argv0.sh $(objpfx)ld.so \
'$(test-wrapper-env)' '$(run_program_env)' \
'$(rpath-link)' 'test-argv0' > $@; \
$(evaluate-test)
+
+$(objpfx)list-tunables.out: $(objpfx)ld.so
+ $(objpfx)ld.so --list-tunables > $@; \
+ $(evaluate-test)
@@ -63,7 +63,7 @@ struct audit_list
enum rtld_mode
{
rtld_mode_normal, rtld_mode_list, rtld_mode_verify, rtld_mode_trace,
- rtld_mode_help,
+ rtld_mode_list_tunables, rtld_mode_help,
};
/* Aggregated state information extracted from environment variables
@@ -398,6 +398,42 @@ __tunables_init (char **envp)
}
}
+void
+__tunables_print (void)
+{
+ for (int i = 0; i < sizeof (tunable_list) / sizeof (tunable_t); i++)
+ {
+ tunable_t *cur = &tunable_list[i];
+ _dl_printf ("%s: ", cur->name);
+ switch (cur->type.type_code)
+ {
+ case TUNABLE_TYPE_INT_32:
+ _dl_printf ("%d (min: %d, max: %d)\n",
+ (int) cur->val.numval,
+ (int) cur->type.min,
+ (int) cur->type.max);
+ break;
+ case TUNABLE_TYPE_UINT_64:
+ _dl_printf ("0x%lx (min: 0x%lx, max: 0x%lx)\n",
+ (long int) cur->val.numval,
+ (long int) cur->type.min,
+ (long int) cur->type.max);
+ break;
+ case TUNABLE_TYPE_SIZE_T:
+ _dl_printf ("0x%Zx (min: 0x%Zx, max: 0x%Zx)\n",
+ (size_t) cur->val.numval,
+ (size_t) cur->type.min,
+ (size_t) cur->type.max);
+ break;
+ case TUNABLE_TYPE_STRING:
+ _dl_printf ("%s\n", cur->val.strval ? cur->val.strval : "");
+ break;
+ default:
+ __builtin_unreachable ();
+ }
+ }
+}
+
/* Set the tunable value. This is called by the module that the tunable exists
in. */
void
@@ -69,9 +69,11 @@ typedef struct _tunable tunable_t;
# include "dl-tunable-list.h"
extern void __tunables_init (char **);
+extern void __tunables_print (void);
extern void __tunable_get_val (tunable_id_t, void *, tunable_callback_t);
extern void __tunable_set_val (tunable_id_t, void *, void *, void *);
rtld_hidden_proto (__tunables_init)
+rtld_hidden_proto (__tunables_print)
rtld_hidden_proto (__tunable_get_val)
rtld_hidden_proto (__tunable_set_val)
@@ -190,7 +190,12 @@ setting environment variables (which would be inherited by subprocesses).\n\
in LIST\n\
--audit LIST use objects named in LIST as auditors\n\
--preload LIST preload objects named in LIST\n\
- --argv0 STRING set argv[0] to STRING before running\n\
+ --argv0 STRING set argv[0] to STRING before running\n"
+#if HAVE_TUNABLES
+"\
+ --list-tunables list all tunables with minimum and maximum values\n"
+#endif
+"\
--help display this help and exit\n\
--version output version information and exit\n\
\n\
@@ -49,6 +49,10 @@
#include <libc-early-init.h>
#include <dl-main.h>
+#if HAVE_TUNABLES
+# include <dl-tunables.h>
+#endif
+
#include <assert.h>
/* Only enables rtld profiling for architectures which provides non generic
@@ -1248,6 +1252,16 @@ dl_main (const ElfW(Phdr) *phdr,
_dl_argc -= 2;
_dl_argv += 2;
}
+#if HAVE_TUNABLES
+ else if (! strcmp (_dl_argv[1], "--list-tunables"))
+ {
+ state.mode = rtld_mode_list_tunables;
+
+ ++_dl_skip_args;
+ --_dl_argc;
+ ++_dl_argv;
+ }
+#endif
else if (strcmp (_dl_argv[1], "--help") == 0)
{
state.mode = rtld_mode_help;
@@ -1268,6 +1282,15 @@ dl_main (const ElfW(Phdr) *phdr,
else
break;
+#if HAVE_TUNABLES
+ if (__builtin_expect (state.mode, rtld_mode_normal)
+ == rtld_mode_list_tunables)
+ {
+ __tunables_print ();
+ _exit (0);
+ }
+#endif
+
/* If we have no further argument the program was called incorrectly.
Grant the user some education. */
if (_dl_argc < 2)
@@ -28,6 +28,43 @@ Finally, the set of tunables available may vary between distributions as
the tunables feature allows distributions to add their own tunables under
their own namespace.
+Passing @option{--list-tunables} to the dynamic loader to print all
+tunables with minimum and maximum values:
+
+@example
+$ /lib64/ld-linux-x86-64.so.2 --list-tunables
+glibc.rtld.nns: 0x4 (min: 0x1, max: 0x10)
+glibc.elision.skip_lock_after_retries: 3 (min: -2147483648, max: 2147483647)
+glibc.malloc.trim_threshold: 0x0 (min: 0x0, max: 0xffffffffffffffff)
+glibc.malloc.perturb: 0 (min: 0, max: 255)
+glibc.cpu.x86_shared_cache_size: 0x100000 (min: 0x0, max: 0xffffffffffffffff)
+glibc.elision.tries: 3 (min: -2147483648, max: 2147483647)
+glibc.elision.enable: 0 (min: 0, max: 1)
+glibc.cpu.x86_rep_movsb_threshold: 0x800 (min: 0x100, max: 0xffffffffffffffff)
+glibc.malloc.mxfast: 0x0 (min: 0x0, max: 0xffffffffffffffff)
+glibc.elision.skip_lock_busy: 3 (min: -2147483648, max: 2147483647)
+glibc.malloc.top_pad: 0x0 (min: 0x0, max: 0xffffffffffffffff)
+glibc.cpu.x86_rep_stosb_threshold: 0x800 (min: 0x1, max: 0xffffffffffffffff)
+glibc.cpu.x86_non_temporal_threshold: 0xc0000 (min: 0x0, max: 0xffffffffffffffff)
+glibc.cpu.x86_shstk:
+glibc.cpu.hwcap_mask: 0x6 (min: 0x0, max: 0xffffffffffffffff)
+glibc.malloc.mmap_max: 0 (min: -2147483648, max: 2147483647)
+glibc.elision.skip_trylock_internal_abort: 3 (min: -2147483648, max: 2147483647)
+glibc.malloc.tcache_unsorted_limit: 0x0 (min: 0x0, max: 0xffffffffffffffff)
+glibc.cpu.x86_ibt:
+glibc.cpu.hwcaps:
+glibc.elision.skip_lock_internal_abort: 3 (min: -2147483648, max: 2147483647)
+glibc.malloc.arena_max: 0x0 (min: 0x1, max: 0xffffffffffffffff)
+glibc.malloc.mmap_threshold: 0x0 (min: 0x0, max: 0xffffffffffffffff)
+glibc.cpu.x86_data_cache_size: 0x8000 (min: 0x0, max: 0xffffffffffffffff)
+glibc.malloc.tcache_count: 0x0 (min: 0x0, max: 0xffffffffffffffff)
+glibc.malloc.arena_test: 0x0 (min: 0x1, max: 0xffffffffffffffff)
+glibc.pthread.mutex_spin_count: 100 (min: 0, max: 32767)
+glibc.rtld.optional_static_tls: 0x200 (min: 0x0, max: 0xffffffffffffffff)
+glibc.malloc.tcache_max: 0x0 (min: 0x0, max: 0xffffffffffffffff)
+glibc.malloc.check: 0 (min: 0, max: 3)
+@end example
+
@menu
* Tunable names:: The structure of a tunable name
* Memory Allocation Tunables:: Tunables in the memory allocation subsystem