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Add opt hpa_hugify_sync to hugify synchronously

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Linux 6.1 introduced `MADV_COLLAPSE` flag to perform a best-effort
synchronous collapse of the native pages mapped by the memory range into
transparent huge pages.

Synchronous hugification might be beneficial for at least two reasons:
we are not relying on khugepaged anymore and get an instant feedback if
range wasn't hugified.

If `hpa_hugify_sync` option is on, we'll try to perform synchronously
collapse and if it wasn't successful, we'll fallback to asynchronous
behaviour.
This commit is contained in:
Dmitry Ilvokhin 2024-10-31 11:43:11 -07:00 • committed by stanjo74
parent a361e886e2
commit 0ce13c6fb5
15 changed files with 141 additions and 8 deletions
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17
src/hpa.c
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@ -210,6 +210,7 @@ hpa_shard_init(hpa_shard_t *shard, hpa_central_t *central, emap_t *emap,
shard->stats.npurge_passes = 0;
shard->stats.npurges = 0;
shard->stats.nhugifies = 0;
shard->stats.nhugify_failures = 0;
shard->stats.ndehugifies = 0;
/*
@ -242,6 +243,7 @@ hpa_shard_nonderived_stats_accum(hpa_shard_nonderived_stats_t *dst,
dst->npurge_passes += src->npurge_passes;
dst->npurges += src->npurges;
dst->nhugifies += src->nhugifies;
dst->nhugify_failures += src->nhugify_failures;
dst->ndehugifies += src->ndehugifies;
}
@ -499,10 +501,23 @@ hpa_try_hugify(tsdn_t *tsdn, hpa_shard_t *shard) {
malloc_mutex_unlock(tsdn, &shard->mtx);
shard->central->hooks.hugify(hpdata_addr_get(to_hugify), HUGEPAGE);
bool err = shard->central->hooks.hugify(hpdata_addr_get(to_hugify),
HUGEPAGE, shard->opts.hugify_sync);
malloc_mutex_lock(tsdn, &shard->mtx);
shard->stats.nhugifies++;
if (err) {
/*
* When asynchronious hugification is used
* (shard->opts.hugify_sync option is false), we are not
* expecting to get here, unless something went terrible wrong.
* Because underlying syscall is only setting kernel flag for
* memory range (actual hugification happens asynchroniously
* and we are not getting any feedback about its outcome), we
* expect syscall to be successful all the time.
*/
shard->stats.nhugify_failures++;
}
psset_update_begin(&shard->psset, to_hugify);
hpdata_hugify(to_hugify);