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Tcache: make slot sizing configurable.

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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
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49
src/tcache.c
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@@ -10,8 +10,13 @@
/******************************************************************************/
/* Data. */
bool opt_tcache = true;
ssize_t opt_lg_tcache_max = LG_TCACHE_MAXCLASS_DEFAULT;
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
@@ -19,7 +24,7 @@ ssize_t opt_lg_tcache_max = LG_TCACHE_MAXCLASS_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;
}
}