Author: markj Date: Mon Oct 19 16:57:40 2020 New Revision: 366840 URL: https://svnweb.freebsd.org/changeset/base/366840
Log: uma: Respect uk_reserve in keg_drain() When a reserve of free items is configured for a zone, the reserve must not be reclaimed under memory pressure. Modify keg_drain() to simply respect the reserved pool. While here remove an always-false uk_freef == NULL check (kegs that shouldn't be drained should set _NOFREE instead), and make sure that the keg_drain() KTR statement does not reference an uninitialized variable. Reviewed by: alc, rlibby Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D26772 Modified: head/sys/vm/uma_core.c Modified: head/sys/vm/uma_core.c ============================================================================== --- head/sys/vm/uma_core.c Mon Oct 19 16:55:03 2020 (r366839) +++ head/sys/vm/uma_core.c Mon Oct 19 16:57:40 2020 (r366840) @@ -1415,47 +1415,81 @@ keg_free_slab(uma_keg_t keg, uma_slab_t slab, int star uma_total_dec(PAGE_SIZE * keg->uk_ppera); } -/* - * Frees pages from a keg back to the system. This is done on demand from - * the pageout daemon. - * - * Returns nothing. - */ static void -keg_drain(uma_keg_t keg) +keg_drain_domain(uma_keg_t keg, int domain) { struct slabhead freeslabs; uma_domain_t dom; uma_slab_t slab, tmp; - int i, n; + uint32_t i, stofree, stokeep, partial; - if (keg->uk_flags & UMA_ZONE_NOFREE || keg->uk_freef == NULL) - return; + dom = &keg->uk_domain[domain]; + LIST_INIT(&freeslabs); - for (i = 0; i < vm_ndomains; i++) { - CTR4(KTR_UMA, "keg_drain %s(%p) domain %d free items: %u", - keg->uk_name, keg, i, dom->ud_free_items); - dom = &keg->uk_domain[i]; - LIST_INIT(&freeslabs); + CTR4(KTR_UMA, "keg_drain %s(%p) domain %d free items: %u", + keg->uk_name, keg, i, dom->ud_free_items); - KEG_LOCK(keg, i); - if ((keg->uk_flags & UMA_ZFLAG_HASH) != 0) { - LIST_FOREACH(slab, &dom->ud_free_slab, us_link) - UMA_HASH_REMOVE(&keg->uk_hash, slab); - } - n = dom->ud_free_slabs; + KEG_LOCK(keg, domain); + + /* + * Are the free items in partially allocated slabs sufficient to meet + * the reserve? If not, compute the number of fully free slabs that must + * be kept. + */ + partial = dom->ud_free_items - dom->ud_free_slabs * keg->uk_ipers; + if (partial < keg->uk_reserve) { + stokeep = min(dom->ud_free_slabs, + howmany(keg->uk_reserve - partial, keg->uk_ipers)); + } else { + stokeep = 0; + } + stofree = dom->ud_free_slabs - stokeep; + + /* + * Partition the free slabs into two sets: those that must be kept in + * order to maintain the reserve, and those that may be released back to + * the system. Since one set may be much larger than the other, + * populate the smaller of the two sets and swap them if necessary. + */ + for (i = min(stofree, stokeep); i > 0; i--) { + slab = LIST_FIRST(&dom->ud_free_slab); + LIST_REMOVE(slab, us_link); + LIST_INSERT_HEAD(&freeslabs, slab, us_link); + } + if (stofree > stokeep) LIST_SWAP(&freeslabs, &dom->ud_free_slab, uma_slab, us_link); - dom->ud_free_slabs = 0; - dom->ud_free_items -= n * keg->uk_ipers; - dom->ud_pages -= n * keg->uk_ppera; - KEG_UNLOCK(keg, i); - LIST_FOREACH_SAFE(slab, &freeslabs, us_link, tmp) - keg_free_slab(keg, slab, keg->uk_ipers); + if ((keg->uk_flags & UMA_ZFLAG_HASH) != 0) { + LIST_FOREACH(slab, &freeslabs, us_link) + UMA_HASH_REMOVE(&keg->uk_hash, slab); } + dom->ud_free_items -= stofree * keg->uk_ipers; + dom->ud_free_slabs -= stofree; + dom->ud_pages -= stofree * keg->uk_ppera; + KEG_UNLOCK(keg, domain); + + LIST_FOREACH_SAFE(slab, &freeslabs, us_link, tmp) + keg_free_slab(keg, slab, keg->uk_ipers); } +/* + * Frees pages from a keg back to the system. This is done on demand from + * the pageout daemon. + * + * Returns nothing. + */ static void +keg_drain(uma_keg_t keg) +{ + int i; + + if ((keg->uk_flags & UMA_ZONE_NOFREE) != 0) + return; + for (i = 0; i < vm_ndomains; i++) + keg_drain_domain(keg, i); +} + +static void zone_reclaim(uma_zone_t zone, int waitok, bool drain) { @@ -2411,6 +2445,9 @@ zone_alloc_sysctl(uma_zone_t zone, void *unused) SYSCTL_ADD_U32(NULL, SYSCTL_CHILDREN(oid), OID_AUTO, "align", CTLFLAG_RD, &keg->uk_align, 0, "item alignment mask"); + SYSCTL_ADD_U32(NULL, SYSCTL_CHILDREN(oid), OID_AUTO, + "reserve", CTLFLAG_RD, &keg->uk_reserve, 0, + "number of reserved items"); SYSCTL_ADD_PROC(NULL, SYSCTL_CHILDREN(oid), OID_AUTO, "efficiency", CTLFLAG_RD | CTLTYPE_INT | CTLFLAG_MPSAFE, keg, 0, sysctl_handle_uma_slab_efficiency, "I", _______________________________________________ svn-src-all@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
