Date: Sun, 22 Apr 2018 09:30:07 +0000 (UTC) From: Mateusz Guzik <mjg@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r332870 - head/sys/kern Message-ID: <201804220930.w3M9U788051989@repo.freebsd.org>
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Author: mjg Date: Sun Apr 22 09:30:07 2018 New Revision: 332870 URL: https://svnweb.freebsd.org/changeset/base/332870 Log: lockf: slightly depessimize 1. check if P_ADVLOCK is already set and if so, don't lock to set it (stolen from DragonFly) 2. when trying for fast path unlock, check that we are doing unlock first instead of taking the interlock for no reason (e.g. if we want to *lock*). whilere make it more likely that falling fast path will not take the interlock either by checking for state Note the code is severely pessimized both single- and multithreaded. Modified: head/sys/kern/kern_descrip.c head/sys/kern/kern_lockf.c Modified: head/sys/kern/kern_descrip.c ============================================================================== --- head/sys/kern/kern_descrip.c Sun Apr 22 06:11:46 2018 (r332869) +++ head/sys/kern/kern_descrip.c Sun Apr 22 09:30:07 2018 (r332870) @@ -648,9 +648,11 @@ kern_fcntl(struct thread *td, int fd, int cmd, intptr_ error = EBADF; break; } - PROC_LOCK(p->p_leader); - p->p_leader->p_flag |= P_ADVLOCK; - PROC_UNLOCK(p->p_leader); + if ((p->p_leader->p_flag & P_ADVLOCK) == 0) { + PROC_LOCK(p->p_leader); + p->p_leader->p_flag |= P_ADVLOCK; + PROC_UNLOCK(p->p_leader); + } error = VOP_ADVLOCK(vp, (caddr_t)p->p_leader, F_SETLK, flp, flg); break; @@ -659,9 +661,11 @@ kern_fcntl(struct thread *td, int fd, int cmd, intptr_ error = EBADF; break; } - PROC_LOCK(p->p_leader); - p->p_leader->p_flag |= P_ADVLOCK; - PROC_UNLOCK(p->p_leader); + if ((p->p_leader->p_flag & P_ADVLOCK) == 0) { + PROC_LOCK(p->p_leader); + p->p_leader->p_flag |= P_ADVLOCK; + PROC_UNLOCK(p->p_leader); + } error = VOP_ADVLOCK(vp, (caddr_t)p->p_leader, F_SETLK, flp, flg); break; Modified: head/sys/kern/kern_lockf.c ============================================================================== --- head/sys/kern/kern_lockf.c Sun Apr 22 06:11:46 2018 (r332869) +++ head/sys/kern/kern_lockf.c Sun Apr 22 09:30:07 2018 (r332870) @@ -479,15 +479,15 @@ retry_setlock: /* * Avoid the common case of unlocking when inode has no locks. */ - VI_LOCK(vp); - if ((*statep) == NULL) { - if (ap->a_op != F_SETLK) { + if (ap->a_op != F_SETLK && (*statep) == NULL) { + VI_LOCK(vp); + if ((*statep) == NULL) { fl->l_type = F_UNLCK; VI_UNLOCK(vp); return (0); } + VI_UNLOCK(vp); } - VI_UNLOCK(vp); /* * Map our arguments to an existing lock owner or create one
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