diff options
| -rw-r--r-- | ChangeLog | 28 | ||||
| -rw-r--r-- | INSTALL | 6 | ||||
| -rw-r--r-- | NEWS | 8 | ||||
| -rw-r--r-- | config.make.in | 2 | ||||
| -rwxr-xr-x | configure | 13 | ||||
| -rw-r--r-- | configure.ac | 7 | ||||
| -rw-r--r-- | elf/dl-tunables.list | 12 | ||||
| -rw-r--r-- | malloc/Makefile | 5 | ||||
| -rw-r--r-- | malloc/arena.c | 11 | ||||
| -rw-r--r-- | malloc/malloc.c | 350 | ||||
| -rw-r--r-- | manual/install.texi | 6 | ||||
| -rw-r--r-- | manual/probes.texi | 19 | ||||
| -rw-r--r-- | manual/tunables.texi | 32 |
13 files changed, 490 insertions, 9 deletions
@@ -1,3 +1,31 @@ +2017-07-06 DJ Delorie <dj@delorie.com> + + * config.make.in: Enable experimental malloc option. + * configure.ac: Likewise. + * configure: Regenerate. + * manual/install.texi: Document it. + * INSTALL: Regenerate. + * malloc/Makefile: Likewise. + * malloc/malloc.c: Add per-thread cache (tcache). + (tcache_put): New. + (tcache_get): New. + (tcache_thread_freeres): New. + (tcache_init): New. + (__libc_malloc): Use cached chunks if available. + (__libc_free): Initialize tcache if needed. + (__libc_realloc): Likewise. + (__libc_calloc): Likewise. + (_int_malloc): Prefill tcache when appropriate. + (_int_free): Likewise. + (do_set_tcache_max): New. + (do_set_tcache_count): New. + (do_set_tcache_unsorted_limit): New. + * manual/probes.texi: Document new probes. + * malloc/arena.c: Add new tcache tunables. + * elf/dl-tunables.list: Likewise. + * manual/tunables.texi: Document them. + * NEWS: Mention the per-thread cache. + 2017-07-06 Joseph Myers <joseph@codesourcery.com> * iconvdata/tst-loading.c (TIMEOUT): Define to 30. @@ -200,6 +200,12 @@ will be used, and CFLAGS sets optimization options for the compiler. libnss_nisplus are not built at all. Use this option to enable libnsl with all depending NSS modules and header files. +'--disable-experimental-malloc' + By default, a per-thread cache is enabled in 'malloc'. While this + cache can be disabled on a per-application basis using tunables + (set glibc.malloc.tcache_count to zero), this option can be used to + remove it from the build completely. + '--build=BUILD-SYSTEM' '--host=HOST-SYSTEM' These options are for cross-compiling. If you specify both options @@ -9,6 +9,14 @@ Version 2.26 Major new features: +* A per-thread cache has been added to malloc. Access to the cache requires + no locks and therefore significantly accelerates the fast path to allocate + and free small amounts of memory. Refilling an empty cache requires locking + the underlying arena. Performance measurements show significant gains in a + wide variety of user workloads. Workloads were captured using a special + instrumented malloc and analyzed with a malloc simulator. Contributed by + DJ Delorie with the help of Florian Weimer, and Carlos O'Donell. + * Unicode 10.0.0 Support: Character encoding, character type info, and transliteration tables are all updated to Unicode 10.0.0, using generator scripts contributed by Mike FABIAN (Red Hat). diff --git a/config.make.in b/config.make.in index dadabf9..5a4a054 100644 --- a/config.make.in +++ b/config.make.in @@ -78,6 +78,8 @@ 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@ @@ -674,6 +674,7 @@ build_obsolete_nsl link_obsolete_rpc libc_cv_static_nss_crypt libc_cv_nss_crypt +experimental_malloc enable_werror all_warnings force_install @@ -779,6 +780,7 @@ enable_kernel enable_all_warnings enable_werror enable_multi_arch +enable_experimental_malloc enable_nss_crypt enable_obsolete_rpc enable_obsolete_nsl @@ -1450,6 +1452,8 @@ 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 @@ -3522,6 +3526,15 @@ 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 7e03019..77456aa 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 df4f962..c188c6a 100644 --- a/elf/dl-tunables.list +++ b/elf/dl-tunables.list @@ -76,6 +76,18 @@ glibc { minval: 1 security_level: SXID_IGNORE } + tcache_max { + type: SIZE_T + security_level: SXID_ERASE + } + tcache_count { + type: SIZE_T + security_level: SXID_ERASE + } + tcache_unsorted_limit { + type: SIZE_T + security_level: SXID_ERASE + } } tune { hwcap_mask { diff --git a/malloc/Makefile b/malloc/Makefile index b50de7c..3fa395b 100644 --- a/malloc/Makefile +++ b/malloc/Makefile @@ -189,6 +189,11 @@ 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 660d638..dc14fae 100644 --- a/malloc/arena.c +++ b/malloc/arena.c @@ -236,6 +236,11 @@ TUNABLE_CALLBACK_FNDECL (set_perturb_byte, int32_t) TUNABLE_CALLBACK_FNDECL (set_trim_threshold, size_t) TUNABLE_CALLBACK_FNDECL (set_arena_max, size_t) TUNABLE_CALLBACK_FNDECL (set_arena_test, size_t) +#if USE_TCACHE +TUNABLE_CALLBACK_FNDECL (set_tcache_max, size_t) +TUNABLE_CALLBACK_FNDECL (set_tcache_count, size_t) +TUNABLE_CALLBACK_FNDECL (set_tcache_unsorted_limit, size_t) +#endif #else /* Initialization routine. */ #include <string.h> @@ -322,6 +327,12 @@ ptmalloc_init (void) TUNABLE_GET (mmap_max, int32_t, TUNABLE_CALLBACK (set_mmaps_max)); TUNABLE_GET (arena_max, size_t, TUNABLE_CALLBACK (set_arena_max)); TUNABLE_GET (arena_test, size_t, TUNABLE_CALLBACK (set_arena_test)); +#if USE_TCACHE + TUNABLE_GET (tcache_max, size_t, TUNABLE_CALLBACK (set_tcache_max)); + TUNABLE_GET (tcache_count, size_t, TUNABLE_CALLBACK (set_tcache_count)); + TUNABLE_GET (tcache_unsorted_limit, size_t, + TUNABLE_CALLBACK (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 aa45626..2527e25 100644 --- a/malloc/malloc.c +++ b/malloc/malloc.c @@ -238,6 +238,9 @@ /* For ALIGN_UP et. al. */ #include <libc-pointer-arith.h> +/* For DIAG_PUSH/POP_NEEDS_COMMENT et al. */ +#include <libc-diag.h> + #include <malloc/malloc-internal.h> /* @@ -296,6 +299,30 @@ __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 @@ -1712,6 +1739,17 @@ 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 @@ -1750,6 +1788,13 @@ 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. */ @@ -2875,6 +2920,124 @@ 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) { @@ -2885,6 +3048,23 @@ __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 (); + + DIAG_PUSH_NEEDS_COMMENT; + 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); + } + DIAG_POP_NEEDS_COMMENT; +#endif arena_get (ar_ptr, bytes); @@ -2944,6 +3124,8 @@ __libc_free (void *mem) return; } + MAYBE_INIT_TCACHE (); + ar_ptr = arena_for_chunk (p); _int_free (ar_ptr, p, 0); } @@ -2981,7 +3163,10 @@ __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 @@ -3206,6 +3391,8 @@ __libc_calloc (size_t n, size_t elem_size) sz = bytes; + MAYBE_INIT_TCACHE (); + arena_get (av, sz); if (av) { @@ -3336,6 +3523,10 @@ _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; /* @@ -3365,19 +3556,22 @@ _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)) @@ -3388,6 +3582,26 @@ _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; @@ -3426,6 +3640,32 @@ _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; @@ -3464,6 +3704,16 @@ _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; @@ -3524,10 +3774,26 @@ _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 */ @@ -3594,11 +3860,31 @@ _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. @@ -3884,6 +4170,20 @@ _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. @@ -4845,6 +5145,38 @@ 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/install.texi b/manual/install.texi index 03eb2dd..b8deb9ce 100644 --- a/manual/install.texi +++ b/manual/install.texi @@ -232,6 +232,12 @@ libnss_nisplus are not built at all. Use this option to enable libnsl with all depending NSS modules and header files. +@item --disable-experimental-malloc +By default, a per-thread cache is enabled in @code{malloc}. While +this cache can be disabled on a per-application basis using tunables +(set glibc.malloc.tcache_count to zero), this option can be used to +remove it from the build completely. + @item --build=@var{build-system} @itemx --host=@var{host-system} These options are for cross-compiling. If you specify both options and 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 9331b03..b16d591 100644 --- a/manual/tunables.texi +++ b/manual/tunables.texi @@ -193,6 +193,38 @@ 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. 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. +@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 chunks +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. + @node Hardware Capability Tunables @section Hardware Capability Tunables @cindex hardware capability tunables |