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Implement process_madvise support.

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Add opt.process_madvise_max_batch which determines if process_madvise is enabled
(non-zero) and the max # of regions in each batch.  Added another limiting
factor which is the space to reserve on stack, which results in the max batch of
128.
This commit is contained in:
Qi Wang 2025-02-04 18:31:11 -08:00 • committed by Qi Wang
parent 70f019cd3a
commit 22440a0207
13 changed files with 204 additions and 6 deletions
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67
src/pac.c
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@ -435,6 +435,44 @@ pac_stash_decayed(tsdn_t *tsdn, pac_t *pac, ecache_t *ecache,
return nstashed;
}
static bool
decay_with_process_madvise(edata_list_inactive_t *decay_extents) {
cassert(have_process_madvise);
assert(opt_process_madvise_max_batch > 0);
#ifndef JEMALLOC_HAVE_PROCESS_MADVISE
return true;
#else
assert(opt_process_madvise_max_batch <=
PROCESS_MADVISE_MAX_BATCH_LIMIT);
size_t len = opt_process_madvise_max_batch;
VARIABLE_ARRAY(struct iovec, vec, len);
size_t cur = 0, total_bytes = 0;
for (edata_t *edata = edata_list_inactive_first(decay_extents);
edata != NULL;
edata = edata_list_inactive_next(decay_extents, edata)) {
size_t pages_bytes = edata_size_get(edata);
vec[cur].iov_base = edata_base_get(edata);
vec[cur].iov_len = pages_bytes;
total_bytes += pages_bytes;
cur++;
if (cur == len) {
bool err = pages_purge_process_madvise(vec, len,
total_bytes);
if (err) {
return true;
}
cur = 0;
total_bytes = 0;
}
}
if (cur > 0) {
return pages_purge_process_madvise(vec, cur, total_bytes);
}
return false;
#endif
}
static size_t
pac_decay_stashed(tsdn_t *tsdn, pac_t *pac, decay_t *decay,
pac_decay_stats_t *decay_stats, ecache_t *ecache, bool fully_decay,
@ -450,6 +488,28 @@ pac_decay_stashed(tsdn_t *tsdn, pac_t *pac, decay_t *decay,
bool try_muzzy = !fully_decay
&& pac_decay_ms_get(pac, extent_state_muzzy) != 0;
bool purge_to_retained = !try_muzzy ||
ecache->state == extent_state_muzzy;
/*
* Attempt process_madvise only if 1) enabled, 2) purging to retained,
* and 3) not using custom hooks.
*/
bool try_process_madvise = (opt_process_madvise_max_batch > 0) &&
purge_to_retained && ehooks_dalloc_will_fail(ehooks);
bool already_purged;
if (try_process_madvise) {
/*
* If anything unexpected happened during process_madvise
* (e.g. not supporting MADV_DONTNEED, or partial success for
* some reason), we will consider nothing is purged and fallback
* to the regular madvise.
*/
already_purged = !decay_with_process_madvise(decay_extents);
} else {
already_purged = false;
}
for (edata_t *edata = edata_list_inactive_first(decay_extents); edata !=
NULL; edata = edata_list_inactive_first(decay_extents)) {
edata_list_inactive_remove(decay_extents, edata);
@ -473,7 +533,12 @@ pac_decay_stashed(tsdn_t *tsdn, pac_t *pac, decay_t *decay,
}
JEMALLOC_FALLTHROUGH;
case extent_state_muzzy:
extent_dalloc_wrapper(tsdn, pac, ehooks, edata);
if (already_purged) {
extent_dalloc_wrapper_purged(tsdn, pac, ehooks,
edata);
} else {
extent_dalloc_wrapper(tsdn, pac, ehooks, edata);
}
nunmapped += npages;
break;
case extent_state_active: