Date: Fri, 19 Dec 2025 09:19:01 +0000 From: Olivier Certner <olce@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org Subject: git: b987035c2af7 - stable/14 - uma_core: Rely on domainset iterator to wait on M_WAITOK Message-ID: <69451885.3de78.7a4e9eb3@gitrepo.freebsd.org>
index | next in thread | raw e-mail
The branch stable/14 has been updated by olce: URL: https://cgit.FreeBSD.org/src/commit/?id=b987035c2af7adb56f8a89253e09a0f4ead1beb7 commit b987035c2af7adb56f8a89253e09a0f4ead1beb7 Author: Olivier Certner <olce@FreeBSD.org> AuthorDate: 2025-09-08 17:37:35 +0000 Commit: Olivier Certner <olce@FreeBSD.org> CommitDate: 2025-12-19 09:16:43 +0000 uma_core: Rely on domainset iterator to wait on M_WAITOK Commit 8b987a77691d ("Use per-domain keg locks.") removed the need to lock the keg entirely, replacing it with per-domain keg locks. In particular, it removed the need to hold a lock over waiting for a domain to grow free memory. Simplify the code of keg_fetch_slab() and uma_prealloc() by removing the M_WAITOK -> M_NOWAIT downgrade and the local call to vm_wait_doms() (which used to necessitate temporary dropping the keg lock) which the iterator machinery already handles on M_WAITOK (and compatibly with vm_domainset_iter_ignore() at that, although that does not matter now). Reviewed by: bnovkov, markj Tested by: bnovkov MFC after: 3 days Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D52441 (cherry picked from commit 781802df7a2bfe224ef17596d56cf83c49517655) --- sys/vm/uma_core.c | 22 ++++++---------------- 1 file changed, 6 insertions(+), 16 deletions(-) diff --git a/sys/vm/uma_core.c b/sys/vm/uma_core.c index dbac8cd3db27..4a6413fd1669 100644 --- a/sys/vm/uma_core.c +++ b/sys/vm/uma_core.c @@ -3976,21 +3976,15 @@ restart: /* * Use the keg's policy if upper layers haven't already specified a * domain (as happens with first-touch zones). - * - * To avoid races we run the iterator with the keg lock held, but that - * means that we cannot allow the vm_domainset layer to sleep. Thus, - * clear M_WAITOK and handle low memory conditions locally. */ rr = rdomain == UMA_ANYDOMAIN; + aflags = flags; if (rr) { - aflags = (flags & ~M_WAITOK) | M_NOWAIT; if (vm_domainset_iter_policy_ref_init(&di, &keg->uk_dr, &domain, &aflags) != 0) return (NULL); - } else { - aflags = flags; + } else domain = rdomain; - } for (;;) { slab = keg_fetch_free_slab(keg, domain, rr, flags); @@ -4020,13 +4014,8 @@ restart: if ((flags & M_WAITOK) == 0) break; vm_wait_domain(domain); - } else if (vm_domainset_iter_policy(&di, &domain) != 0) { - if ((flags & M_WAITOK) != 0) { - vm_wait_doms(&keg->uk_dr.dr_policy->ds_mask, 0); - goto restart; - } + } else if (vm_domainset_iter_policy(&di, &domain) != 0) break; - } } /* @@ -5212,7 +5201,7 @@ uma_prealloc(uma_zone_t zone, int items) KEG_GET(zone, keg); slabs = howmany(items, keg->uk_ipers); while (slabs-- > 0) { - aflags = M_NOWAIT; + aflags = M_WAITOK; if (vm_domainset_iter_policy_ref_init(&di, &keg->uk_dr, &domain, &aflags) != 0) panic("%s: Domainset is empty", __func__); @@ -5233,7 +5222,8 @@ uma_prealloc(uma_zone_t zone, int items) break; } if (vm_domainset_iter_policy(&di, &domain) != 0) - vm_wait_doms(&keg->uk_dr.dr_policy->ds_mask, 0); + panic("%s: Cannot allocate from any domain", + __func__); } } }help
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?69451885.3de78.7a4e9eb3>