Add opt.lg_extent_max_active_fit

When allocating from dirty extents (which we always prefer if available), large
active extents can get split even if the new allocation is much smaller, in
which case the introduced fragmentation causes high long term damage.  This new
option controls the threshold to reuse and split an existing active extent.  We
avoid using a large extent for much smaller sizes, in order to reduce
fragmentation.  In some workload, adding the threshold improves virtual memory
usage by >10x.
This commit is contained in:
Qi Wang 2017-11-09 13:51:39 -08:00 committed by Qi Wang
parent 282a3faa17
commit fac706836f
7 changed files with 44 additions and 3 deletions

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@ -1069,6 +1069,22 @@ mallctl("arena." STRINGIFY(MALLCTL_ARENAS_ALL) ".decay",
for related dynamic control options.</para></listitem>
</varlistentry>
<varlistentry id="opt.lg_extent_max_active_fit">
<term>
<mallctl>opt.lg_extent_max_active_fit</mallctl>
(<type>size_t</type>)
<literal>r-</literal>
</term>
<listitem><para>When reusing dirty extents, this determines the (log
base 2 of the) maximum ratio between the size of the active extent
selected (to split off from) and the size of the requested allocation.
This prevents the splitting of large active extents for smaller
allocations, which can reduce fragmentation over the long run
(especially for non-active extents). Lower value may reduce
fragmentation, at the cost of extra active extents. The default value
is 6, which gives a maximum ratio of 64 (2^6).</para></listitem>
</varlistentry>
<varlistentry id="opt.stats_print">
<term>
<mallctl>opt.stats_print</mallctl>

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@ -6,9 +6,11 @@
#include "jemalloc/internal/ph.h"
#include "jemalloc/internal/rtree.h"
extern rtree_t extents_rtree;
extern const extent_hooks_t extent_hooks_default;
extern mutex_pool_t extent_mutex_pool;
extern size_t opt_lg_extent_max_active_fit;
extern rtree_t extents_rtree;
extern const extent_hooks_t extent_hooks_default;
extern mutex_pool_t extent_mutex_pool;
extent_t *extent_alloc(tsdn_t *tsdn, arena_t *arena);
void extent_dalloc(tsdn_t *tsdn, arena_t *arena, extent_t *extent);

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@ -8,4 +8,10 @@ typedef struct extents_s extents_t;
#define EXTENT_GROW_MAX_PIND (NPSIZES - 1)
/*
* When reuse (and split) an active extent, (1U << opt_lg_extent_max_active_fit)
* is the max ratio between the size of the active extent and the new extent.
*/
#define LG_EXTENT_MAX_ACTIVE_FIT_DEFAULT 6
#endif /* JEMALLOC_INTERNAL_EXTENT_TYPES_H */

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@ -95,6 +95,7 @@ CTL_PROTO(opt_zero)
CTL_PROTO(opt_utrace)
CTL_PROTO(opt_xmalloc)
CTL_PROTO(opt_tcache)
CTL_PROTO(opt_lg_extent_max_active_fit)
CTL_PROTO(opt_lg_tcache_max)
CTL_PROTO(opt_prof)
CTL_PROTO(opt_prof_prefix)
@ -293,6 +294,7 @@ static const ctl_named_node_t opt_node[] = {
{NAME("utrace"), CTL(opt_utrace)},
{NAME("xmalloc"), CTL(opt_xmalloc)},
{NAME("tcache"), CTL(opt_tcache)},
{NAME("lg_extent_max_active_fit"), CTL(opt_lg_extent_max_active_fit)},
{NAME("lg_tcache_max"), CTL(opt_lg_tcache_max)},
{NAME("prof"), CTL(opt_prof)},
{NAME("prof_prefix"), CTL(opt_prof_prefix)},
@ -1597,6 +1599,8 @@ CTL_RO_NL_CGEN(config_fill, opt_zero, opt_zero, bool)
CTL_RO_NL_CGEN(config_utrace, opt_utrace, opt_utrace, bool)
CTL_RO_NL_CGEN(config_xmalloc, opt_xmalloc, opt_xmalloc, bool)
CTL_RO_NL_GEN(opt_tcache, opt_tcache, bool)
CTL_RO_NL_GEN(opt_lg_extent_max_active_fit, opt_lg_extent_max_active_fit,
size_t)
CTL_RO_NL_GEN(opt_lg_tcache_max, opt_lg_tcache_max, ssize_t)
CTL_RO_NL_CGEN(config_prof, opt_prof, opt_prof, bool)
CTL_RO_NL_CGEN(config_prof, opt_prof_prefix, opt_prof_prefix, const char *)

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@ -17,6 +17,8 @@ rtree_t extents_rtree;
/* Keyed by the address of the extent_t being protected. */
mutex_pool_t extent_mutex_pool;
size_t opt_lg_extent_max_active_fit = LG_EXTENT_MAX_ACTIVE_FIT_DEFAULT;
static const bitmap_info_t extents_bitmap_info =
BITMAP_INFO_INITIALIZER(NPSIZES+1);
@ -369,6 +371,13 @@ extents_best_fit_locked(tsdn_t *tsdn, arena_t *arena, extents_t *extents,
pszind_t i = (pszind_t)bitmap_ffu(extents->bitmap, &extents_bitmap_info,
(size_t)pind);
if (i < NPSIZES+1) {
/*
* In order to reduce fragmentation, avoid reusing and splitting
* large extents for much smaller sizes.
*/
if ((sz_pind2sz(i) >> opt_lg_extent_max_active_fit) > size) {
return NULL;
}
assert(!extent_heap_empty(&extents->heaps[i]));
extent_t *extent = extent_heap_first(&extents->heaps[i]);
assert(extent_size_get(extent) >= size);

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@ -1146,6 +1146,9 @@ malloc_conf_init(void) {
CONF_HANDLE_BOOL(opt_xmalloc, "xmalloc")
}
CONF_HANDLE_BOOL(opt_tcache, "tcache")
CONF_HANDLE_SIZE_T(opt_lg_extent_max_active_fit,
"lg_extent_max_active_fit", 0,
(sizeof(size_t) << 3), yes, yes, false)
CONF_HANDLE_SSIZE_T(opt_lg_tcache_max, "lg_tcache_max",
-1, (sizeof(size_t) << 3) - 1)
if (strncmp("percpu_arena", k, klen) == 0) {

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@ -172,6 +172,7 @@ TEST_BEGIN(test_mallctl_opt) {
TEST_MALLCTL_OPT(bool, utrace, utrace);
TEST_MALLCTL_OPT(bool, xmalloc, xmalloc);
TEST_MALLCTL_OPT(bool, tcache, always);
TEST_MALLCTL_OPT(size_t, lg_extent_max_active_fit, always);
TEST_MALLCTL_OPT(size_t, lg_tcache_max, always);
TEST_MALLCTL_OPT(bool, prof, prof);
TEST_MALLCTL_OPT(const char *, prof_prefix, prof);