Tcache: make slot sizing configurable.

This commit is contained in:
David Goldblatt 2020-05-11 15:03:06 -07:00 committed by David Goldblatt
parent b58dea8d1b
commit 181093173d
5 changed files with 59 additions and 30 deletions

View File

@ -4,6 +4,10 @@
extern bool opt_tcache;
extern ssize_t opt_lg_tcache_max;
extern ssize_t opt_lg_tcache_nslots_mul;
extern unsigned opt_tcache_nslots_small_min;
extern unsigned opt_tcache_nslots_small_max;
extern unsigned opt_tcache_nslots_large;
extern ssize_t opt_lg_tcache_shift;
/*
* Number of tcache bins. There are SC_NBINS small-object bins, plus 0 or more

View File

@ -17,23 +17,6 @@ typedef struct tcaches_s tcaches_t;
#define TCACHE_STATE_PURGATORY ((tcache_t *)(uintptr_t)3)
#define TCACHE_STATE_MAX TCACHE_STATE_PURGATORY
/*
* Absolute minimum number of cache slots for each small bin.
*/
#define TCACHE_NSLOTS_SMALL_MIN 20
/*
* Absolute maximum number of cache slots for each small bin in the thread
* cache. This is an additional constraint beyond that imposed as: twice the
* number of regions per slab for this size class.
*
* This constant must be an even number.
*/
#define TCACHE_NSLOTS_SMALL_MAX 200
/* Number of cache slots for large size classes. */
#define TCACHE_NSLOTS_LARGE 20
/* (1U << opt_lg_tcache_max) is used to compute tcache_maxclass. */
#define LG_TCACHE_MAXCLASS_DEFAULT 15

View File

@ -1379,6 +1379,16 @@ malloc_conf_init_helper(sc_data_t *sc_data, unsigned bin_shard_sizes[SC_NBINS],
*/
CONF_HANDLE_SSIZE_T(opt_lg_tcache_nslots_mul,
"lg_tcache_nslots_mul", -16, 16)
/* Ditto with values past 2048. */
CONF_HANDLE_UNSIGNED(opt_tcache_nslots_small_min,
"tcache_nslots_small_min", 1, 2048,
CONF_CHECK_MIN, CONF_CHECK_MAX, /* clip */ true)
CONF_HANDLE_UNSIGNED(opt_tcache_nslots_small_max,
"tcache_nslots_small_max", 1, 2048,
CONF_CHECK_MIN, CONF_CHECK_MAX, /* clip */ true)
CONF_HANDLE_UNSIGNED(opt_tcache_nslots_large,
"tcache_nslots_large", 1, 2048,
CONF_CHECK_MIN, CONF_CHECK_MAX, /* clip */ true)
/*
* The runtime option of oversize_threshold remains

View File

@ -13,13 +13,18 @@
bool opt_tcache = true;
ssize_t opt_lg_tcache_max = LG_TCACHE_MAXCLASS_DEFAULT;
/* Reasonable defaults for min and max values. */
unsigned opt_tcache_nslots_small_min = 20;
unsigned opt_tcache_nslots_small_max = 200;
unsigned opt_tcache_nslots_large = 20;
/*
* We attempt to make the number of slots in a tcache bin for a given size class
* equal to the number of objects in a slab times some multiplier. By default,
* the multiplier is 1/2 (i.e. we set the maximum number of objects in the
* tcache to half the number of objects in a slab).
* This is bounded by some other constraints as well, like the fact that it
* must be even, must be less than TCACHE_NSLOTS_SMALL_MAX, etc..
* must be even, must be less than opt_tcache_nslots_small_max, etc..
*/
ssize_t opt_lg_tcache_nslots_mul = -1;
@ -485,7 +490,6 @@ tcache_init(tsd_t *tsd, tcache_slow_t *tcache_slow, tcache_t *tcache,
tcache_slow->arena = NULL;
tcache_slow->dyn_alloc = mem;
assert((TCACHE_NSLOTS_SMALL_MAX & 1U) == 0);
memset(tcache->bins, 0, sizeof(cache_bin_t) * nhbins);
size_t cur_offset = 0;
@ -792,10 +796,37 @@ static unsigned
tcache_ncached_max_compute(szind_t szind) {
if (szind >= SC_NBINS) {
assert(szind < nhbins);
return TCACHE_NSLOTS_LARGE;
return opt_tcache_nslots_large;
}
unsigned slab_nregs = bin_infos[szind].nregs;
/* We may modify these values; start with the opt versions. */
unsigned nslots_small_min = opt_tcache_nslots_small_min;
unsigned nslots_small_max = opt_tcache_nslots_small_max;
/*
* Clamp values to meet our constraints -- even, nonzero, min < max, and
* suitable for a cache bin size.
*/
if (opt_tcache_nslots_small_max > CACHE_BIN_NCACHED_MAX) {
nslots_small_max = CACHE_BIN_NCACHED_MAX;
}
if (nslots_small_min % 2 != 0) {
nslots_small_min++;
}
if (nslots_small_max % 2 != 0) {
nslots_small_max--;
}
if (nslots_small_min < 2) {
nslots_small_min = 2;
}
if (nslots_small_max < 2) {
nslots_small_max = 2;
}
if (nslots_small_min > nslots_small_max) {
nslots_small_min = nslots_small_max;
}
unsigned candidate;
if (opt_lg_tcache_nslots_mul < 0) {
candidate = slab_nregs >> (-opt_lg_tcache_nslots_mul);
@ -810,12 +841,12 @@ tcache_ncached_max_compute(szind_t szind) {
*/
++candidate;
}
if (candidate <= TCACHE_NSLOTS_SMALL_MIN) {
return TCACHE_NSLOTS_SMALL_MIN;
} else if (candidate <= TCACHE_NSLOTS_SMALL_MAX) {
if (candidate <= nslots_small_min) {
return nslots_small_min;
} else if (candidate <= nslots_small_max) {
return candidate;
} else {
return TCACHE_NSLOTS_SMALL_MAX;
return nslots_small_max;
}
}

View File

@ -53,12 +53,13 @@ do_flush_test(cache_bin_t *bin, cache_bin_info_t *info, void **ptrs,
}
TEST_BEGIN(test_cache_bin) {
const int ncached_max = 100;
bool success;
void *ptr;
cache_bin_t bin;
cache_bin_info_t info;
cache_bin_info_init(&info, TCACHE_NSLOTS_SMALL_MAX);
cache_bin_info_init(&info, ncached_max);
size_t size;
size_t alignment;
@ -74,7 +75,7 @@ TEST_BEGIN(test_cache_bin) {
assert_zu_eq(cur_offset, size, "Should use all requested memory");
/* Initialize to empty; should then have 0 elements. */
cache_bin_sz_t ncached_max = cache_bin_info_ncached_max(&info);
expect_d_eq(ncached_max, cache_bin_info_ncached_max(&info), "");
expect_true(cache_bin_ncached_get(&bin, &info) == 0, "");
expect_true(cache_bin_low_water_get(&bin, &info) == 0, "");