Date: Sun, 27 Aug 2023 22:45:15 GMT From: Mateusz Guzik <mjg@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org Subject: git: b18ab4f29540 - stable/13 - vfs: trylock vnode requeue Message-ID: <202308272245.37RMjFqw003047@gitrepo.freebsd.org>
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The branch stable/13 has been updated by mjg: URL: https://cgit.FreeBSD.org/src/commit/?id=b18ab4f2954019f70b5f8cf879e76675f3d4425b commit b18ab4f2954019f70b5f8cf879e76675f3d4425b Author: Mateusz Guzik <mjg@FreeBSD.org> AuthorDate: 2023-03-21 04:23:15 +0000 Commit: Mateusz Guzik <mjg@FreeBSD.org> CommitDate: 2023-08-27 22:44:12 +0000 vfs: trylock vnode requeue The quasi-LRU still gets in the way for example when doing an incremental bzImage build, with vnode_list lock being at the top of the profile. Further damage control the problem by trylocking. Note the entire mechanism desperately wants to be reaped out in favor of something(tm) which both scales in a multicore setting and provides sensible replacement policy. With this change everything vfs almost disappears from the on CPU flamegraph, what is left is tons of contention in the VM. (cherry picked from commit 138a5dafba312ff39ce0eefdbe34de95519e600d) --- sys/kern/vfs_subr.c | 26 +++++++++++++++++--------- 1 file changed, 17 insertions(+), 9 deletions(-) diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c index 5cdefca60e7c..c1c474b6724d 100644 --- a/sys/kern/vfs_subr.c +++ b/sys/kern/vfs_subr.c @@ -3533,17 +3533,25 @@ vdbatch_process(struct vdbatch *vd) MPASS(curthread->td_pinned > 0); MPASS(vd->index == VDBATCH_SIZE); - mtx_lock(&vnode_list_mtx); critical_enter(); - for (i = 0; i < VDBATCH_SIZE; i++) { - vp = vd->tab[i]; - TAILQ_REMOVE(&vnode_list, vp, v_vnodelist); - TAILQ_INSERT_TAIL(&vnode_list, vp, v_vnodelist); - MPASS(vp->v_dbatchcpu != NOCPU); - vp->v_dbatchcpu = NOCPU; + if (mtx_trylock(&vnode_list_mtx)) { + for (i = 0; i < VDBATCH_SIZE; i++) { + vp = vd->tab[i]; + vd->tab[i] = NULL; + TAILQ_REMOVE(&vnode_list, vp, v_vnodelist); + TAILQ_INSERT_TAIL(&vnode_list, vp, v_vnodelist); + MPASS(vp->v_dbatchcpu != NOCPU); + vp->v_dbatchcpu = NOCPU; + } + mtx_unlock(&vnode_list_mtx); + } else { + for (i = 0; i < VDBATCH_SIZE; i++) { + vp = vd->tab[i]; + vd->tab[i] = NULL; + MPASS(vp->v_dbatchcpu != NOCPU); + vp->v_dbatchcpu = NOCPU; + } } - mtx_unlock(&vnode_list_mtx); - bzero(vd->tab, sizeof(vd->tab)); vd->index = 0; critical_exit(); }
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