From patchwork Thu May 11 21:31:16 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: DJ Delorie X-Patchwork-Id: 20421 Received: (qmail 61611 invoked by alias); 11 May 2017 21:31:35 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Delivered-To: mailing list libc-alpha@sourceware.org Received: (qmail 61351 invoked by uid 89); 11 May 2017 21:31:28 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-26.1 required=5.0 tests=BAYES_00, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3, KAM_ASCII_DIVIDERS, RP_MATCHES_RCVD, SPF_HELO_PASS autolearn=ham version=3.3.2 spammy=201701, amounted, pulled X-HELO: mx1.redhat.com DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 6A257C04B94B Authentication-Results: ext-mx07.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx07.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=dj@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 6A257C04B94B From: DJ Delorie To: libc-alpha@sourceware.org Cc: "Carlos O'Donell" , Florian Weimer Subject: Re: [updated patch] malloc per-thread cache ready for review In-Reply-To: <9b6d2a24-aa72-cc71-5ede-581dcbd3504d@redhat.com> (carlos@redhat.com) Date: Thu, 11 May 2017 17:31:16 -0400 Message-ID: MIME-Version: 1.0 Inline comments and updated patch attached... Florian Weimer writes: > These type names remind me of Turbo Vision. I don't think we use the > CamelCase convention in glibc. :) DeCamelCased (I did a lot of my early programming in TurboC) > I would like to see some discussion of the per-thread overhead the > thread cache introduces, maybe along the documentation of the tunables, > both the static overhead (due to new per-thread state) and some bounds > on the additional per-thread allocation retention. I put some math in the tunables docs, and also see https://sourceware.org/ml/libc-alpha/2017-01/msg00452.html where this was discussed upstream. "Carlos O'Donell" writes: > - Adding legacy environment variables. Not OK. Removed. > - Missing manual documentation for new tcache tunables. Not OK. > - Missing manual documentation for new probes. Not OK. Added. > The malloc tunables should all be 'security_level: SXID_IGNORE'. Done. > In _int_malloc we have some code duplication where tcache and the normal > code both do the same thing e.g. remove a block. Can we avoid some of > this duplication with a first refactoring patch? I pulled out the common parts, it amounted to only a few lines but they're complex enough to warrant it. > Must be -DUSE_TCACHE=1, please follow -Wundef rules: Done. >> +#if USE_TCACHE >> +/* We want 64 entries. This is an arbitrary limit, which tunables can reduce. */ >> +# define MAX_TCACHE_SIZE (MALLOC_ALIGNMENT * 63) > > Why use 63? Is it because 0 is reserved for the empty zero byte set? If so then just > say "We want 63 non-zero sized entries."? I changed it to 64 and tweaked the macros so that all 64 bins are used (and re-audited them to make sure they were all consistent), which means the largest cacheable size is just over a power of two now (1032 and 516 bytes). Note sure how having this new power-of-two size included will affect the benchmarks, though - previously, the limit was just below those powers-of-two. >> +# define TCACHE_IDX ((MAX_TCACHE_SIZE / MALLOC_ALIGNMENT) + 1) > > Since this is the maximum index can we call this TCACHE_MAX_IDX? It's not a max, it's a size. I renamed it to TACHE_MAX_BINS. >> +# define size2tidx_(bytes) (((bytes) + MALLOC_ALIGNMENT - 1) / MALLOC_ALIGNMENT) > > Why the trailing underscore? Explanation elided, as I ended up removing it anyway. >> +/* Rounds up, so... >> + idx 0 bytes 0 >> + idx 1 bytes 1..8 >> + idx 2 bytes 9..16 >> + etc. */ > > This doesn't look correct for a 64-bit x86_64 system (maybe 32-bit?). > > Could you please adjust the comment for 64-bit x86_64 where MALLOC_ALIGNMENT > should be 16 bytes, and indicate the comment is for that given machine. Tweaked. >> +/* This is another arbitrary limit, which tunables can change. */ >> +# define TCACHE_FILL_COUNT 7 > > Comment should describe in more detail what a developer should need to > know about this. Done. The tunables docs have more info too. >> + /* Maximum number of chunks to remove from the unsorted list, which >> + don't match. */ > > Which don't match what? Don't match the cache line we're trying to fill. Edited. >> +typedef struct TCacheEntry { >> + struct TCacheEntry *next; >> +} TCacheEntry; > > Needs explaining in detail that these apparently incomplete types are layered > on top of a chunk. Done. >> +/* There is one of these for each thread, which contains the >> + per-thread cache (hence "TCache"). Keeping overall size low is >> + mildly important. Note that COUNTS and ENTRIES are redundant, this >> + is for performance reasons. */ > > Why do you say they are redundant? Because you could in theory have a thread > local pointer to TCacheEntry and walk that list when a malloc request arrives? > If so, please expand the comment to cover that. Yes. Done. >> +static void >> +tcache_put (mchunkptr chunk, size_t tc_idx) >> +{ >> + TCacheEntry *e = (TCacheEntry *) chunk2mem (chunk); > > Can we assert the safety of tc_idx? assert (tc_idx < TCACHE_IDX); ? I noted in a comment that it's the caller's responsibility to be safe, and the code is only ever used inside suitable conditionals for index and count, but I added asserts anyway. > Please add a comment here that in a low-memory condition we will have > victim == NULL and tcache == NULL and keep calling tcache_init > at every opportunity to eventually get enough memory for the tcache. Done. In such a condition, there won't be enough memory to do much of anything, though... >> +#if USE_TCACHE >> + INTERNAL_SIZE_T tcache_nb = 0; >> + size_t tc_idx = csize2tidx (nb); >> + if (tcache && tc_idx < mp_.tcache_max) >> + tcache_nb = nb; >> + int return_cached = 0; >> + >> + tcache_unsorted_count = 0; > > We selectively apply this limit to just unsorted, but why not all the > other places where we iterate filling the cache? Because in the other > cases we have perfect size matches we know we want? I noted in the tunables doc that scanning the other lists is bounded, since the other lists always have known sizes. The unsorted list may be unbounded, and the non-matching chunks we find have to be processed and sorted, which makes that expensive. Hence, I added a user-definable limit here just for that list. ====================================================================== diff --git a/config.make.in b/config.make.in index 5836b32..0290d83 100644 --- a/config.make.in +++ b/config.make.in @@ -77,6 +77,8 @@ multi-arch = @multi_arch@ mach-interface-list = @mach_interface_list@ +experimental-malloc = @experimental_malloc@ + nss-crypt = @libc_cv_nss_crypt@ static-nss-crypt = @libc_cv_static_nss_crypt@ diff --git a/configure b/configure index eecd0ac..b80fd4d 100755 --- a/configure +++ b/configure @@ -672,6 +672,7 @@ build_nscd link_obsolete_rpc libc_cv_static_nss_crypt libc_cv_nss_crypt +experimental_malloc enable_werror all_warnings force_install @@ -777,6 +778,7 @@ enable_kernel enable_all_warnings enable_werror enable_multi_arch +enable_experimental_malloc enable_nss_crypt enable_obsolete_rpc enable_systemtap @@ -1447,6 +1449,8 @@ Optional Features: --disable-werror do not build with -Werror --enable-multi-arch enable single DSO with optimizations for multiple architectures + --disable-experimental-malloc + disable experimental malloc features --enable-nss-crypt enable libcrypt to use nss --enable-obsolete-rpc build and install the obsolete RPC code for link-time usage @@ -3517,6 +3521,15 @@ else fi +# Check whether --enable-experimental-malloc was given. +if test "${enable_experimental_malloc+set}" = set; then : + enableval=$enable_experimental_malloc; experimental_malloc=$enableval +else + experimental_malloc=yes +fi + + + # Check whether --enable-nss-crypt was given. if test "${enable_nss_crypt+set}" = set; then : enableval=$enable_nss_crypt; nss_crypt=$enableval diff --git a/configure.ac b/configure.ac index 4a77411..b929012 100644 --- a/configure.ac +++ b/configure.ac @@ -313,6 +313,13 @@ AC_ARG_ENABLE([multi-arch], [multi_arch=$enableval], [multi_arch=default]) +AC_ARG_ENABLE([experimental-malloc], + AC_HELP_STRING([--disable-experimental-malloc], + [disable experimental malloc features]), + [experimental_malloc=$enableval], + [experimental_malloc=yes]) +AC_SUBST(experimental_malloc) + AC_ARG_ENABLE([nss-crypt], AC_HELP_STRING([--enable-nss-crypt], [enable libcrypt to use nss]), diff --git a/elf/dl-tunables.list b/elf/dl-tunables.list index cb9e8f1..af2b46f 100644 --- a/elf/dl-tunables.list +++ b/elf/dl-tunables.list @@ -76,5 +76,17 @@ glibc { minval: 1 security_level: SXID_IGNORE } + tcache_max { + type: SIZE_T + security_level: SXID_IGNORE + } + tcache_count { + type: SIZE_T + security_level: SXID_IGNORE + } + tcache_unsorted_limit { + type: SIZE_T + security_level: SXID_IGNORE + } } } diff --git a/malloc/Makefile b/malloc/Makefile index e93b83b..e6ca11c 100644 --- a/malloc/Makefile +++ b/malloc/Makefile @@ -168,6 +168,11 @@ tst-malloc-usable-static-ENV = $(tst-malloc-usable-ENV) tst-malloc-usable-tunables-ENV = GLIBC_TUNABLES=glibc.malloc.check=3 tst-malloc-usable-static-tunables-ENV = $(tst-malloc-usable-tunables-ENV) +ifeq ($(experimental-malloc),yes) +CPPFLAGS-malloc.c += -DUSE_TCACHE=1 +else +CPPFLAGS-malloc.c += -DUSE_TCACHE=0 +endif # Uncomment this for test releases. For public releases it is too expensive. #CPPFLAGS-malloc.o += -DMALLOC_DEBUG=1 diff --git a/malloc/arena.c b/malloc/arena.c index d49e4a2..dacc481 100644 --- a/malloc/arena.c +++ b/malloc/arena.c @@ -236,6 +236,11 @@ DL_TUNABLE_CALLBACK_FNDECL (set_perturb_byte, int32_t) DL_TUNABLE_CALLBACK_FNDECL (set_trim_threshold, size_t) DL_TUNABLE_CALLBACK_FNDECL (set_arena_max, size_t) DL_TUNABLE_CALLBACK_FNDECL (set_arena_test, size_t) +#if USE_TCACHE +DL_TUNABLE_CALLBACK_FNDECL (set_tcache_max, size_t) +DL_TUNABLE_CALLBACK_FNDECL (set_tcache_count, size_t) +DL_TUNABLE_CALLBACK_FNDECL (set_tcache_unsorted_limit, size_t) +#endif #else /* Initialization routine. */ #include @@ -322,6 +327,12 @@ ptmalloc_init (void) TUNABLE_SET_VAL_WITH_CALLBACK (mmap_max, NULL, set_mmaps_max); TUNABLE_SET_VAL_WITH_CALLBACK (arena_max, NULL, set_arena_max); TUNABLE_SET_VAL_WITH_CALLBACK (arena_test, NULL, set_arena_test); +#if USE_TCACHE + TUNABLE_SET_VAL_WITH_CALLBACK (tcache_max, NULL, set_tcache_max); + TUNABLE_SET_VAL_WITH_CALLBACK (tcache_count, NULL, set_tcache_count); + TUNABLE_SET_VAL_WITH_CALLBACK (tcache_unsorted_limit, NULL, + set_tcache_unsorted_limit); +#endif __libc_lock_unlock (main_arena.mutex); #else const char *s = NULL; diff --git a/malloc/malloc.c b/malloc/malloc.c index e29105c..d904db8 100644 --- a/malloc/malloc.c +++ b/malloc/malloc.c @@ -297,6 +297,30 @@ __malloc_assert (const char *assertion, const char *file, unsigned int line, } #endif +#if USE_TCACHE +/* We want 64 entries. This is an arbitrary limit, which tunables can reduce. */ +# define TCACHE_MAX_BINS 64 +# define MAX_TCACHE_SIZE tidx2usize (TCACHE_MAX_BINS-1) + +/* Only used to pre-fill the tunables. */ +# define tidx2usize(idx) (((size_t) idx) * MALLOC_ALIGNMENT + MINSIZE - SIZE_SZ) + +/* When "x" is from chunksize(). */ +# define csize2tidx(x) (((x) - MINSIZE + MALLOC_ALIGNMENT - 1) / MALLOC_ALIGNMENT) +/* When "x" is a user-provided size. */ +# define usize2tidx(x) csize2tidx (request2size (x)) + +/* With rounding and alignment, the bins are... + idx 0 bytes 0..24 (64-bit) or 0..12 (32-bit) + idx 1 bytes 25..40 or 13..20 + idx 2 bytes 41..56 or 21..28 + etc. */ + +/* This is another arbitrary limit, which tunables can change. Each + tcache bin will hold at most this number of chunks. */ +# define TCACHE_FILL_COUNT 7 +#endif + /* REALLOC_ZERO_BYTES_FREES should be set if a call to @@ -1711,6 +1735,17 @@ struct malloc_par /* First address handed out by MORECORE/sbrk. */ char *sbrk_base; + +#if USE_TCACHE + /* Maximum number of buckets to use. */ + size_t tcache_bins; + size_t tcache_max_bytes; + /* Maximum number of chunks in each bucket. */ + size_t tcache_count; + /* Maximum number of chunks to remove from the unsorted list, which + aren't used to prefill the cache. */ + size_t tcache_unsorted_limit; +#endif }; /* There are several instances of this struct ("arenas") in this @@ -1749,6 +1784,13 @@ static struct malloc_par mp_ = .trim_threshold = DEFAULT_TRIM_THRESHOLD, #define NARENAS_FROM_NCORES(n) ((n) * (sizeof (long) == 4 ? 2 : 8)) .arena_test = NARENAS_FROM_NCORES (1) +#if USE_TCACHE + , + .tcache_count = TCACHE_FILL_COUNT, + .tcache_bins = TCACHE_MAX_BINS, + .tcache_max_bytes = tidx2usize (TCACHE_MAX_BINS-1), + .tcache_unsorted_limit = 0 /* No limit. */ +#endif }; /* Maximum size of memory handled in fastbins. */ @@ -2874,6 +2916,121 @@ mremap_chunk (mchunkptr p, size_t new_size) /*------------------------ Public wrappers. --------------------------------*/ +#if USE_TCACHE + +/* We overlay this structure on the user-data portion of a chunk when + the chunk is stored in the per-thread cache. */ +typedef struct tcache_entry { + struct tcache_entry *next; +} tcache_entry; + +/* There is one of these for each thread, which contains the + per-thread cache (hence "tcache_perthread_struct"). Keeping + overall size low is mildly important. Note that COUNTS and ENTRIES + are redundant (we could have just counted the linked list each + time), this is for performance reasons. */ +typedef struct tcache_perthread_struct { + char counts[TCACHE_MAX_BINS]; + tcache_entry *entries[TCACHE_MAX_BINS]; +} tcache_perthread_struct; + +static __thread char tcache_shutting_down = 0; +static __thread tcache_perthread_struct *tcache = NULL; + +/* Caller must ensure that we know tc_idx is valid and there's room + for more chunks. */ +static void +tcache_put (mchunkptr chunk, size_t tc_idx) +{ + tcache_entry *e = (tcache_entry *) chunk2mem (chunk); + assert (tc_idx < TCACHE_MAX_BINS); + e->next = tcache->entries[tc_idx]; + tcache->entries[tc_idx] = e; + ++(tcache->counts[tc_idx]); +} + +/* Caller must ensure that we know tc_idx is valid and there's + available chunks to remove. */ +static void * +tcache_get (size_t tc_idx) +{ + tcache_entry *e = tcache->entries[tc_idx]; + assert (tc_idx < TCACHE_MAX_BINS); + assert (tcache->entries[tc_idx] > 0); + tcache->entries[tc_idx] = e->next; + --(tcache->counts[tc_idx]); + return (void *) e; +} + +static void __attribute__ ((section ("__libc_thread_freeres_fn"))) +tcache_thread_freeres (void) +{ + int i; + tcache_perthread_struct *tcache_tmp = tcache; + + if (!tcache) + return; + + tcache = NULL; + + for (i = 0; i < TCACHE_MAX_BINS; ++i) { + while (tcache_tmp->entries[i]) + { + tcache_entry *e = tcache_tmp->entries[i]; + tcache_tmp->entries[i] = e->next; + __libc_free (e); + } + } + + __libc_free (tcache_tmp); + + tcache_shutting_down = 1; +} +text_set_element (__libc_thread_subfreeres, tcache_thread_freeres); + +static void +tcache_init(void) +{ + mstate ar_ptr; + void *victim = 0; + const size_t bytes = sizeof (tcache_perthread_struct); + + if (tcache_shutting_down) + return; + + arena_get (ar_ptr, bytes); + victim = _int_malloc (ar_ptr, bytes); + if (!victim && ar_ptr != NULL) + { + ar_ptr = arena_get_retry (ar_ptr, bytes); + victim = _int_malloc (ar_ptr, bytes); + } + + + if (ar_ptr != NULL) + __libc_lock_unlock (ar_ptr->mutex); + + /* In a low memory situation, we may not be able to allocate memory + - in which case, we just keep trying later. However, we + typically do this very early, so either there is sufficient + memory, or there isn't enough memory to do non-trivial + allocations anyway. */ + if (victim) + { + tcache = (tcache_perthread_struct *) victim; + memset (tcache, 0, sizeof (tcache_perthread_struct)); + } + +} + +#define MAYBE_INIT_TCACHE() \ + if (__glibc_unlikely (tcache == NULL)) \ + tcache_init(); + +#else +#define MAYBE_INIT_TCACHE() +#endif + void * __libc_malloc (size_t bytes) { @@ -2884,6 +3041,21 @@ __libc_malloc (size_t bytes) = atomic_forced_read (__malloc_hook); if (__builtin_expect (hook != NULL, 0)) return (*hook)(bytes, RETURN_ADDRESS (0)); +#if USE_TCACHE + /* int_free also calls request2size, be careful to not pad twice. */ + size_t tbytes = request2size (bytes); + size_t tc_idx = csize2tidx (tbytes); + + MAYBE_INIT_TCACHE (); + + if (tc_idx < mp_.tcache_bins + && tc_idx < TCACHE_MAX_BINS /* to appease gcc */ + && tcache + && tcache->entries[tc_idx] != NULL) + { + return tcache_get (tc_idx); + } +#endif arena_get (ar_ptr, bytes); @@ -2943,6 +3115,8 @@ __libc_free (void *mem) return; } + MAYBE_INIT_TCACHE (); + ar_ptr = arena_for_chunk (p); _int_free (ar_ptr, p, 0); } @@ -2980,7 +3154,10 @@ __libc_realloc (void *oldmem, size_t bytes) if (chunk_is_mmapped (oldp)) ar_ptr = NULL; else - ar_ptr = arena_for_chunk (oldp); + { + MAYBE_INIT_TCACHE (); + ar_ptr = arena_for_chunk (oldp); + } /* Little security check which won't hurt performance: the allocator never wrapps around at the end of the address space. Therefore @@ -3205,6 +3382,8 @@ __libc_calloc (size_t n, size_t elem_size) sz = bytes; + MAYBE_INIT_TCACHE (); + arena_get (av, sz); if (av) { @@ -3335,6 +3514,10 @@ _int_malloc (mstate av, size_t bytes) mchunkptr fwd; /* misc temp for linking */ mchunkptr bck; /* misc temp for linking */ +#if USE_TCACHE + size_t tcache_unsorted_count; /* count of unsorted chunks processed */ +#endif + const char *errstr = NULL; /* @@ -3364,19 +3547,22 @@ _int_malloc (mstate av, size_t bytes) can try it without checking, which saves some time on this fast path. */ +#define REMOVE_FB(fb, victim, pp) \ + do \ + { \ + victim = pp; \ + if (victim == NULL) \ + break; \ + } \ + while ((pp = catomic_compare_and_exchange_val_acq (fb, victim->fd, victim)) \ + != victim); \ + if ((unsigned long) (nb) <= (unsigned long) (get_max_fast ())) { idx = fastbin_index (nb); mfastbinptr *fb = &fastbin (av, idx); mchunkptr pp = *fb; - do - { - victim = pp; - if (victim == NULL) - break; - } - while ((pp = catomic_compare_and_exchange_val_acq (fb, victim->fd, victim)) - != victim); + REMOVE_FB (fb, victim, pp); if (victim != 0) { if (__builtin_expect (fastbin_index (chunksize (victim)) != idx, 0)) @@ -3387,6 +3573,26 @@ _int_malloc (mstate av, size_t bytes) return NULL; } check_remalloced_chunk (av, victim, nb); +#if USE_TCACHE + /* While we're here, if we see other chunks of the same size, + stash them in the tcache. */ + size_t tc_idx = csize2tidx (nb); + if (tcache && tc_idx < mp_.tcache_bins) + { + mchunkptr tc_victim; + + /* While bin not empty and tcache not full, copy chunks over. */ + while (tcache->counts[tc_idx] < mp_.tcache_count + && (pp = *fb) != NULL) + { + REMOVE_FB (fb, tc_victim, pp); + if (tc_victim != 0) + { + tcache_put (tc_victim, tc_idx); + } + } + } +#endif void *p = chunk2mem (victim); alloc_perturb (p, bytes); return p; @@ -3425,6 +3631,32 @@ _int_malloc (mstate av, size_t bytes) if (av != &main_arena) set_non_main_arena (victim); check_malloced_chunk (av, victim, nb); +#if USE_TCACHE + /* While we're here, if we see other chunks of the same size, + stash them in the tcache. */ + size_t tc_idx = csize2tidx (nb); + if (tcache && tc_idx < mp_.tcache_bins) + { + mchunkptr tc_victim; + + /* While bin not empty and tcache not full, copy chunks over. */ + while (tcache->counts[tc_idx] < mp_.tcache_count + && (tc_victim = last (bin)) != bin) + { + if (tc_victim != 0) + { + bck = tc_victim->bk; + set_inuse_bit_at_offset (tc_victim, nb); + if (av != &main_arena) + set_non_main_arena (tc_victim); + bin->bk = bck; + bck->fd = bin; + + tcache_put (tc_victim, tc_idx); + } + } + } +#endif void *p = chunk2mem (victim); alloc_perturb (p, bytes); return p; @@ -3463,6 +3695,16 @@ _int_malloc (mstate av, size_t bytes) otherwise need to expand memory to service a "small" request. */ +#if USE_TCACHE + INTERNAL_SIZE_T tcache_nb = 0; + size_t tc_idx = csize2tidx (nb); + if (tcache && tc_idx < mp_.tcache_bins) + tcache_nb = nb; + int return_cached = 0; + + tcache_unsorted_count = 0; +#endif + for (;; ) { int iters = 0; @@ -3523,10 +3765,26 @@ _int_malloc (mstate av, size_t bytes) set_inuse_bit_at_offset (victim, size); if (av != &main_arena) set_non_main_arena (victim); +#if USE_TCACHE + /* Fill cache first, return to user only if cache fills. + We may return one of these chunks later. */ + if (tcache_nb + && tcache->counts[tc_idx] < mp_.tcache_count) + { + tcache_put (victim, tc_idx); + return_cached = 1; + continue; + } + else + { +#endif check_malloced_chunk (av, victim, nb); void *p = chunk2mem (victim); alloc_perturb (p, bytes); return p; +#if USE_TCACHE + } +#endif } /* place chunk in bin */ @@ -3593,11 +3851,31 @@ _int_malloc (mstate av, size_t bytes) fwd->bk = victim; bck->fd = victim; +#if USE_TCACHE + /* If we've processed as many chunks as we're allowed while + filling the cache, return one of the cached ones. */ + ++tcache_unsorted_count; + if (return_cached + && mp_.tcache_unsorted_limit > 0 + && tcache_unsorted_count > mp_.tcache_unsorted_limit) + { + return tcache_get (tc_idx); + } +#endif + #define MAX_ITERS 10000 if (++iters >= MAX_ITERS) break; } +#if USE_TCACHE + /* If all the small chunks we found ended up cached, return one now. */ + if (return_cached) + { + return tcache_get (tc_idx); + } +#endif + /* If a large request, scan through the chunks of current bin in sorted order to find smallest that fits. Use the skip list for this. @@ -3883,6 +4161,20 @@ _int_free (mstate av, mchunkptr p, int have_lock) check_inuse_chunk(av, p); +#if USE_TCACHE + { + size_t tc_idx = csize2tidx (size); + + if (tcache + && tc_idx < mp_.tcache_bins + && tcache->counts[tc_idx] < mp_.tcache_count) + { + tcache_put (p, tc_idx); + return; + } + } +#endif + /* If eligible, place chunk on a fastbin so it can be found and used quickly in malloc. @@ -4844,6 +5136,38 @@ do_set_arena_max (size_t value) return 1; } +#if USE_TCACHE +static inline int +__always_inline +do_set_tcache_max (size_t value) +{ + if (value >= 0 && value <= MAX_TCACHE_SIZE) + { + LIBC_PROBE (memory_tunable_tcache_max_bytes, 2, value, mp_.tcache_max_bytes); + mp_.tcache_max_bytes = value; + mp_.tcache_bins = csize2tidx (request2size(value)) + 1; + } + return 1; +} + +static inline int +__always_inline +do_set_tcache_count (size_t value) +{ + LIBC_PROBE (memory_tunable_tcache_count, 2, value, mp_.tcache_count); + mp_.tcache_count = value; + return 1; +} + +static inline int +__always_inline +do_set_tcache_unsorted_limit (size_t value) +{ + LIBC_PROBE (memory_tunable_tcache_unsorted_limit, 2, value, mp_.tcache_unsorted_limit); + mp_.tcache_unsorted_limit = value; + return 1; +} +#endif int __libc_mallopt (int param_number, int value) diff --git a/manual/probes.texi b/manual/probes.texi index eb91c62..96acaed 100644 --- a/manual/probes.texi +++ b/manual/probes.texi @@ -231,6 +231,25 @@ dynamic brk/mmap thresholds. Argument @var{$arg1} and @var{$arg2} are the adjusted mmap and trim thresholds, respectively. @end deftp +@deftp Probe memory_tunable_tcache_max_bytes (int @var{$arg1}, int @var{$arg2}) +This probe is triggered when the @code{glibc.malloc.tcache_max} +tunable is set. Argument @var{$arg1} is the requested value, and +@var{$arg2} is the previous value of this tunable. +@end deftp + +@deftp Probe memory_tunable_tcache_count (int @var{$arg1}, int @var{$arg2}) +This probe is triggered when the @code{glibc.malloc.tcache_count} +tunable is set. Argument @var{$arg1} is the requested value, and +@var{$arg2} is the previous value of this tunable. +@end deftp + +@deftp Probe memory_tunable_tcache_unsorted_limit (int @var{$arg1}, int @var{$arg2}) +This probe is triggered when the +@code{glibc.malloc.tcache_unsorted_limit} tunable is set. Argument +@var{$arg1} is the requested value, and @var{$arg2} is the previous +value of this tunable. +@end deftp + @node Mathematical Function Probes @section Mathematical Function Probes diff --git a/manual/tunables.texi b/manual/tunables.texi index ac8c38f..b651a1d 100644 --- a/manual/tunables.texi +++ b/manual/tunables.texi @@ -190,3 +190,37 @@ number of arenas is determined by the number of CPU cores online. For 32-bit systems the limit is twice the number of cores online and on 64-bit systems, it is 8 times the number of cores online. @end deftp + +@deftp Tunable glibc.malloc.tcache_max +The maximum size of a request (in bytes) which may be met via the +per-thread cache. The default (and maximum) value is 1032 bytes on +64-bit systems and 516 bytes on 32-bit systems. +@end deftp + +@deftp Tunable glibc.malloc.tcache_count +The maximum number of chunks of each size to cache. The default is 7. +There is no upper limit, other than available system memory. Note +that chunks are rounded up to malloc's guaranteed alignment - this +count is per rounded size, not per user-provided size. + +The approximate maximum overhead of the per-thread cache (for each +thread, of course) is thus @code{glibc.malloc.tcache_max} (in bins, +max 64 bins) times @code{glibc.malloc.tcache_count} times the size for +each bin. With defaults, this is about 236 KB on 64-bit systems and +118 KB on 32-bit systems. +@end deftp + +@deftp Tunable glibc.malloc.tcache_unsorted_limit +When the user requests memory and the request cannot be met via the +per-thread cache, the arenas are used to meet the request. At this +time, additional chunks will be moved from existing arena lists to +pre-fill the corresponding cache. While copies from the fastbins, +smallbins, and regular bins are bounded and predictable due to the bin +sizes, copies from the unsorted bin are not bounded, and incur +additional time penalties as they need to be sorted as they're +scanned. To make scanning the unsorted list more predictable and +bounded, the user may set this tunable to limit the number of blocks +that are scanned from the unsorted list while searching for chunks to +pre-fill the per-thread cache with. The default, or when set to zero, +is no limit. +@end deftp