From owner-svn-src-head@freebsd.org Sun May 24 03:50:50 2020 Return-Path: Delivered-To: svn-src-head@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 74F212F9A60; Sun, 24 May 2020 03:50:50 +0000 (UTC) (envelope-from mjg@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 49V5qG2YHYz4Fjf; Sun, 24 May 2020 03:50:50 +0000 (UTC) (envelope-from mjg@FreeBSD.org) Received: from repo.freebsd.org (repo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id 526B51AFD9; Sun, 24 May 2020 03:50:50 +0000 (UTC) (envelope-from mjg@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id 04O3oojE012967; Sun, 24 May 2020 03:50:50 GMT (envelope-from mjg@FreeBSD.org) Received: (from mjg@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id 04O3on61012965; Sun, 24 May 2020 03:50:49 GMT (envelope-from mjg@FreeBSD.org) Message-Id: <202005240350.04O3on61012965@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: mjg set sender to mjg@FreeBSD.org using -f From: Mateusz Guzik Date: Sun, 24 May 2020 03:50:49 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r361429 - in head/sys: kern sys X-SVN-Group: head X-SVN-Commit-Author: mjg X-SVN-Commit-Paths: in head/sys: kern sys X-SVN-Commit-Revision: 361429 X-SVN-Commit-Repository: base MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.33 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 24 May 2020 03:50:50 -0000 Author: mjg Date: Sun May 24 03:50:49 2020 New Revision: 361429 URL: https://svnweb.freebsd.org/changeset/base/361429 Log: vfs: scale foffset_lock by using atomics instead of serializing on mtx pool Contending cases still serialize on sleepq (which would be taken anyway). Reviewed by: kib (previous version) Differential Revision: https://reviews.freebsd.org/D21626 Modified: head/sys/kern/vfs_vnops.c head/sys/sys/file.h Modified: head/sys/kern/vfs_vnops.c ============================================================================== --- head/sys/kern/vfs_vnops.c Sat May 23 23:38:35 2020 (r361428) +++ head/sys/kern/vfs_vnops.c Sun May 24 03:50:49 2020 (r361429) @@ -71,6 +71,7 @@ __FBSDID("$FreeBSD$"); #include #include #include +#include #include #include #include @@ -674,8 +675,9 @@ vn_rdwr_inchunks(enum uio_rw rw, struct vnode *vp, voi off_t foffset_lock(struct file *fp, int flags) { - struct mtx *mtxp; + volatile short *flagsp; off_t res; + short state; KASSERT((flags & FOF_OFFSET) == 0, ("FOF_OFFSET passed")); @@ -692,52 +694,66 @@ foffset_lock(struct file *fp, int flags) * According to McKusick the vn lock was protecting f_offset here. * It is now protected by the FOFFSET_LOCKED flag. */ - mtxp = mtx_pool_find(mtxpool_sleep, fp); - mtx_lock(mtxp); - if ((flags & FOF_NOLOCK) == 0) { - while (fp->f_vnread_flags & FOFFSET_LOCKED) { - fp->f_vnread_flags |= FOFFSET_LOCK_WAITING; - msleep(&fp->f_vnread_flags, mtxp, PUSER -1, - "vofflock", 0); + flagsp = &fp->f_vnread_flags; + if (atomic_cmpset_acq_16(flagsp, 0, FOFFSET_LOCKED)) + return (fp->f_offset); + + sleepq_lock(&fp->f_vnread_flags); + state = atomic_load_16(flagsp); + for (;;) { + if ((state & FOFFSET_LOCKED) == 0) { + if (!atomic_fcmpset_acq_16(flagsp, &state, + FOFFSET_LOCKED)) + continue; + break; } - fp->f_vnread_flags |= FOFFSET_LOCKED; + if ((state & FOFFSET_LOCK_WAITING) == 0) { + if (!atomic_fcmpset_acq_16(flagsp, &state, + state | FOFFSET_LOCK_WAITING)) + continue; + } + DROP_GIANT(); + sleepq_add(&fp->f_vnread_flags, NULL, "vofflock", 0, 0); + sleepq_wait(&fp->f_vnread_flags, PUSER -1); + PICKUP_GIANT(); + sleepq_lock(&fp->f_vnread_flags); + state = atomic_load_16(flagsp); } res = fp->f_offset; - mtx_unlock(mtxp); + sleepq_release(&fp->f_vnread_flags); return (res); } void foffset_unlock(struct file *fp, off_t val, int flags) { - struct mtx *mtxp; + volatile short *flagsp; + short state; KASSERT((flags & FOF_OFFSET) == 0, ("FOF_OFFSET passed")); -#if OFF_MAX <= LONG_MAX - if ((flags & FOF_NOLOCK) != 0) { - if ((flags & FOF_NOUPDATE) == 0) - fp->f_offset = val; - if ((flags & FOF_NEXTOFF) != 0) - fp->f_nextoff = val; - return; - } -#endif - - mtxp = mtx_pool_find(mtxpool_sleep, fp); - mtx_lock(mtxp); if ((flags & FOF_NOUPDATE) == 0) fp->f_offset = val; if ((flags & FOF_NEXTOFF) != 0) fp->f_nextoff = val; - if ((flags & FOF_NOLOCK) == 0) { - KASSERT((fp->f_vnread_flags & FOFFSET_LOCKED) != 0, - ("Lost FOFFSET_LOCKED")); - if (fp->f_vnread_flags & FOFFSET_LOCK_WAITING) - wakeup(&fp->f_vnread_flags); - fp->f_vnread_flags = 0; - } - mtx_unlock(mtxp); + +#if OFF_MAX <= LONG_MAX + if ((flags & FOF_NOLOCK) != 0) + return; +#endif + + flagsp = &fp->f_vnread_flags; + state = atomic_load_16(flagsp); + if ((state & FOFFSET_LOCK_WAITING) == 0 && + atomic_cmpset_rel_16(flagsp, state, 0)) + return; + + sleepq_lock(&fp->f_vnread_flags); + MPASS((fp->f_vnread_flags & FOFFSET_LOCKED) != 0); + MPASS((fp->f_vnread_flags & FOFFSET_LOCK_WAITING) != 0); + fp->f_vnread_flags = 0; + sleepq_broadcast(&fp->f_vnread_flags, SLEEPQ_SLEEP, 0, 0); + sleepq_release(&fp->f_vnread_flags); } void Modified: head/sys/sys/file.h ============================================================================== --- head/sys/sys/file.h Sat May 23 23:38:35 2020 (r361428) +++ head/sys/sys/file.h Sun May 24 03:50:49 2020 (r361429) @@ -163,7 +163,7 @@ struct fileops { * Below is the list of locks that protects members in struct file. * * (a) f_vnode lock required (shared allows both reads and writes) - * (f) protected with mtx_lock(mtx_pool_find(fp)) + * (f) updated with atomics and blocking on sleepq * (d) cdevpriv_mtx * none not locked */