Author: markj Date: Sun Jun 28 21:35:04 2020 New Revision: 362740 URL: https://svnweb.freebsd.org/changeset/base/362740
Log: Fix UMA's first-touch policy on systems with empty domains. Suppose a thread is running on a CPU in a NUMA domain with no physical RAM. When an item is freed to a first-touch zone, it ends up in the cross-domain bucket. When the bucket is full, it gets placed in another domain's bucket queue. However, when allocating an item, UMA will always go to the keg upon a per-CPU cache miss because the empty domain's bucket queue will always be empty. This means that a non-empty domain's bucket queues can grow very rapidly on such systems. For example, it can easily cause mbuf allocation failures when the zone limit is reached. Change cache_alloc() to follow a round-robin policy when running on an empty domain. Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D25355 Modified: head/sys/vm/uma_core.c Modified: head/sys/vm/uma_core.c ============================================================================== --- head/sys/vm/uma_core.c Sun Jun 28 21:34:38 2020 (r362739) +++ head/sys/vm/uma_core.c Sun Jun 28 21:35:04 2020 (r362740) @@ -3398,7 +3398,7 @@ static __noinline bool cache_alloc(uma_zone_t zone, uma_cache_t cache, void *udata, int flags) { uma_bucket_t bucket; - int domain; + int curdomain, domain; bool new; CRITICAL_ASSERT(curthread); @@ -3445,7 +3445,8 @@ cache_alloc(uma_zone_t zone, uma_cache_t cache, void * * the critical section. */ domain = PCPU_GET(domain); - if ((cache_uz_flags(cache) & UMA_ZONE_ROUNDROBIN) != 0) + if ((cache_uz_flags(cache) & UMA_ZONE_ROUNDROBIN) != 0 || + VM_DOMAIN_EMPTY(domain)) domain = zone_domain_highest(zone, domain); bucket = cache_fetch_bucket(zone, cache, domain); if (bucket == NULL) { @@ -3470,7 +3471,8 @@ cache_alloc(uma_zone_t zone, uma_cache_t cache, void * cache = &zone->uz_cpu[curcpu]; if (cache->uc_allocbucket.ucb_bucket == NULL && ((cache_uz_flags(cache) & UMA_ZONE_FIRSTTOUCH) == 0 || - domain == PCPU_GET(domain))) { + (curdomain = PCPU_GET(domain)) == domain || + VM_DOMAIN_EMPTY(curdomain))) { if (new) atomic_add_long(&ZDOM_GET(zone, domain)->uzd_imax, bucket->ub_cnt); @@ -3877,7 +3879,7 @@ zone_alloc_bucket(uma_zone_t zone, void *udata, int do /* Avoid allocs targeting empty domains. */ if (domain != UMA_ANYDOMAIN && VM_DOMAIN_EMPTY(domain)) domain = UMA_ANYDOMAIN; - if ((zone->uz_flags & UMA_ZONE_ROUNDROBIN) != 0) + else if ((zone->uz_flags & UMA_ZONE_ROUNDROBIN) != 0) domain = UMA_ANYDOMAIN; if (zone->uz_max_items > 0) _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
