The branch stable/13 has been updated by mav: URL: https://cgit.FreeBSD.org/src/commit/?id=c27237d62f05f3a1842818c5f3cf87fb861a8402
commit c27237d62f05f3a1842818c5f3cf87fb861a8402 Author: Alexander Motin <[email protected]> AuthorDate: 2022-01-19 00:26:16 +0000 Commit: Alexander Motin <[email protected]> CommitDate: 2022-02-02 00:53:10 +0000 Reduce bufdaemon/bufspacedaemon shutdown time. Before this change bufdaemon and bufspacedaemon threads used kthread_shutdown() to stop activity on system shutdown. The problem is that kthread_shutdown() has no idea about the wait channel and lock used by specific thread to wake them up reliably. As result, up to 9 threads could consume up to 9 seconds to shutdown for no good reason. This change introduces specific shutdown functions, knowing how to properly wake up specific threads, reducing wait for those threads on shutdown/reboot from average 4 seconds to effectively zero. MFC after: 2 weeks Reviewed by: kib, markj Differential Revision: https://reviews.freebsd.org/D33936 (cherry picked from commit b7ff445ffa38282daeab36ce82681ba3f54c8851) --- sys/kern/vfs_bio.c | 108 +++++++++++++++++++++++++++++++++++------------------ 1 file changed, 71 insertions(+), 37 deletions(-) diff --git a/sys/kern/vfs_bio.c b/sys/kern/vfs_bio.c index 5c5cfc8cd5d5..a3cec5d7ec74 100644 --- a/sys/kern/vfs_bio.c +++ b/sys/kern/vfs_bio.c @@ -133,6 +133,7 @@ struct bufdomain { int bd_lim; /* atomics */ int bd_wanted; + bool bd_shutdown; int __aligned(CACHE_LINE_SIZE) bd_numdirtybuffers; int __aligned(CACHE_LINE_SIZE) bd_running; long __aligned(CACHE_LINE_SIZE) bd_bufspace; @@ -340,6 +341,11 @@ static struct mtx_padalign __exclusive_cache_line rbreqlock; */ static struct mtx_padalign __exclusive_cache_line bdirtylock; +/* + * bufdaemon shutdown request and sleep channel. + */ +static bool bd_shutdown; + /* * Wakeup point for bufdaemon, as well as indicator of whether it is already * active. Set to 1 when the bufdaemon is already "on" the queue, 0 when it @@ -628,33 +634,6 @@ bufspace_daemon_wakeup(struct bufdomain *bd) } } -/* - * bufspace_daemon_wait: - * - * Sleep until the domain falls below a limit or one second passes. - */ -static void -bufspace_daemon_wait(struct bufdomain *bd) -{ - /* - * Re-check our limits and sleep. bd_running must be - * cleared prior to checking the limits to avoid missed - * wakeups. The waker will adjust one of bufspace or - * freebuffers prior to checking bd_running. - */ - BD_RUN_LOCK(bd); - atomic_store_int(&bd->bd_running, 0); - if (bd->bd_bufspace < bd->bd_bufspacethresh && - bd->bd_freebuffers > bd->bd_lofreebuffers) { - msleep(&bd->bd_running, BD_RUN_LOCKPTR(bd), PRIBIO|PDROP, - "-", hz); - } else { - /* Avoid spurious wakeups while running. */ - atomic_store_int(&bd->bd_running, 1); - BD_RUN_UNLOCK(bd); - } -} - /* * bufspace_adjust: * @@ -785,6 +764,22 @@ bufspace_wait(struct bufdomain *bd, struct vnode *vp, int gbflags, BD_UNLOCK(bd); } +static void +bufspace_daemon_shutdown(void *arg, int howto __unused) +{ + struct bufdomain *bd = arg; + int error; + + BD_RUN_LOCK(bd); + bd->bd_shutdown = true; + wakeup(&bd->bd_running); + error = msleep(&bd->bd_shutdown, BD_RUN_LOCKPTR(bd), 0, + "bufspace_shutdown", 60 * hz); + BD_RUN_UNLOCK(bd); + if (error != 0) + printf("bufspacedaemon wait error: %d\n", error); +} + /* * bufspace_daemon: * @@ -795,14 +790,14 @@ bufspace_wait(struct bufdomain *bd, struct vnode *vp, int gbflags, static void bufspace_daemon(void *arg) { - struct bufdomain *bd; + struct bufdomain *bd = arg; - EVENTHANDLER_REGISTER(shutdown_pre_sync, kthread_shutdown, curthread, + EVENTHANDLER_REGISTER(shutdown_pre_sync, bufspace_daemon_shutdown, bd, SHUTDOWN_PRI_LAST + 100); - bd = arg; - for (;;) { - kthread_suspend_check(); + BD_RUN_LOCK(bd); + while (!bd->bd_shutdown) { + BD_RUN_UNLOCK(bd); /* * Free buffers from the clean queue until we meet our @@ -852,8 +847,29 @@ bufspace_daemon(void *arg) } maybe_yield(); } - bufspace_daemon_wait(bd); + + /* + * Re-check our limits and sleep. bd_running must be + * cleared prior to checking the limits to avoid missed + * wakeups. The waker will adjust one of bufspace or + * freebuffers prior to checking bd_running. + */ + BD_RUN_LOCK(bd); + if (bd->bd_shutdown) + break; + atomic_store_int(&bd->bd_running, 0); + if (bd->bd_bufspace < bd->bd_bufspacethresh && + bd->bd_freebuffers > bd->bd_lofreebuffers) { + msleep(&bd->bd_running, BD_RUN_LOCKPTR(bd), + PRIBIO, "-", hz); + } else { + /* Avoid spurious wakeups while running. */ + atomic_store_int(&bd->bd_running, 1); + } } + wakeup(&bd->bd_shutdown); + BD_RUN_UNLOCK(bd); + kthread_exit(); } /* @@ -3382,6 +3398,21 @@ buf_flush(struct vnode *vp, struct bufdomain *bd, int target) return (flushed); } +static void +buf_daemon_shutdown(void *arg __unused, int howto __unused) +{ + int error; + + mtx_lock(&bdlock); + bd_shutdown = true; + wakeup(&bd_request); + error = msleep(&bd_shutdown, &bdlock, 0, "buf_daemon_shutdown", + 60 * hz); + mtx_unlock(&bdlock); + if (error != 0) + printf("bufdaemon wait error: %d\n", error); +} + static void buf_daemon() { @@ -3393,7 +3424,7 @@ buf_daemon() /* * This process needs to be suspended prior to shutdown sync. */ - EVENTHANDLER_REGISTER(shutdown_pre_sync, kthread_shutdown, curthread, + EVENTHANDLER_REGISTER(shutdown_pre_sync, buf_daemon_shutdown, NULL, SHUTDOWN_PRI_LAST + 100); /* @@ -3413,12 +3444,10 @@ buf_daemon() */ curthread->td_pflags |= TDP_NORUNNINGBUF | TDP_BUFNEED; mtx_lock(&bdlock); - for (;;) { + while (!bd_shutdown) { bd_request = 0; mtx_unlock(&bdlock); - kthread_suspend_check(); - /* * Save speedupreq for this pass and reset to capture new * requests. @@ -3455,6 +3484,8 @@ buf_daemon() * to avoid endless loops on unlockable buffers. */ mtx_lock(&bdlock); + if (bd_shutdown) + break; if (BIT_EMPTY(BUF_DOMAINS, &bdlodirty)) { /* * We reached our low water mark, reset the @@ -3480,6 +3511,9 @@ buf_daemon() msleep(&bd_request, &bdlock, PVM, "qsleep", hz / 10); } } + wakeup(&bd_shutdown); + mtx_unlock(&bdlock); + kthread_exit(); } /*
