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Remove existing documentation and mention removal of fastbins in mxfast tunable. Improve wording of hugetlb tunable, including default for AArch64. OK for commit? Tested-By: Dimitri John Ledkov diff --git a/manual/tunables.texi b/manual/tunables.texi index 72769428e8cac27723fdec9ad83a92dc0b27415a..5850945a59e8494a2bb315da5a3e919112c5c562 100644 --- a/manual/tunables.texi +++ b/manual/tunables.texi @@ -231,37 +231,29 @@ per-thread cache. The default (and maximum) value is 1032 bytes on @end deftp @deftp Tunable glibc.malloc.tcache_count -The maximum number of chunks of each size to cache. The default is 7. +The maximum number of chunks of each size to cache. The default is 16. The upper limit is 65535. If set to zero, the per-thread cache is effectively disabled. The approximate maximum overhead of the per-thread cache is thus equal to the number of bins times the chunk count in each bin times the size -of each chunk. With defaults, the approximate maximum overhead of the -per-thread cache is approximately 236 KB on 64-bit systems and 118 KB -on 32-bit systems. +of each chunk. @end deftp @deftp Tunable glibc.malloc.mxfast -One of the optimizations @code{malloc} uses is to maintain a series of ``fast -bins'' that hold chunks up to a specific size. The default and -maximum size which may be held this way is 80 bytes on 32-bit systems -or 160 bytes on 64-bit systems. Applications which value size over -speed may choose to reduce the size of requests which are serviced -from fast bins with this tunable. Note that the value specified -includes @code{malloc}'s internal overhead, which is normally the size of one -pointer, so add 4 on 32-bit systems or 8 on 64-bit systems to the size -passed to @code{malloc} for the largest bin size to enable. +This tunable has no effect since the ``fastbins'' have been removed. @end deftp @deftp Tunable glibc.malloc.hugetlb This tunable controls the usage of Huge Pages on @code{malloc} calls. The -default value is @code{0}, which disables any additional support on -@code{malloc}. +default value is @code{0} on most targets. Using @code{0} disables support +that improves use of huge pages in @code{malloc}. However huge pages may +still be created depending on the OS settings. Setting its value to @code{1} enables the use of @code{madvise} with @code{MADV_HUGEPAGE} after memory allocation with @code{mmap}. It is enabled only if the system supports Transparent Huge Page (currently only on Linux). +This is the default used for AArch64. Setting its value to @code{2} enables the use of Huge Page directly with @code{mmap} with the use of @code{MAP_HUGETLB} flag. The huge page size