Author: mav Date: Wed Jul 26 17:45:09 2017 New Revision: 321575 URL: https://svnweb.freebsd.org/changeset/base/321575
Log: MFC r319750: MFV r319741: 8156 dbuf_evict_notify() does not need dbuf_evict_lock illumos/illumos-gate@dbfd9f930004c390a2ce2cf850c71b4f880eef9c https://github.com/illumos/illumos-gate/commit/dbfd9f930004c390a2ce2cf850c71b4f880eef9c https://www.illumos.org/issues/8156 dbuf_evict_notify() holds the dbuf_evict_lock while checking if it should do the eviction itself (because the evict thread is not able to keep up). This can result in massive lock contention. It isn't necessary to hold the lock, because if we make the wrong choice occasionally, nothing bad will happen. Reviewed by: Dan Kimmel <dan.kim...@delphix.com> Reviewed by: Paul Dagnelie <p...@delphix.com> Approved by: Robert Mustacchi <r...@joyent.com> Author: Matthew Ahrens <mahr...@delphix.com> Modified: stable/11/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dbuf.c Directory Properties: stable/11/ (props changed) Modified: stable/11/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dbuf.c ============================================================================== --- stable/11/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dbuf.c Wed Jul 26 17:44:22 2017 (r321574) +++ stable/11/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dbuf.c Wed Jul 26 17:45:09 2017 (r321575) @@ -560,19 +560,15 @@ dbuf_evict_notify(void) if (tsd_get(zfs_dbuf_evict_key) != NULL) return; + /* + * We check if we should evict without holding the dbuf_evict_lock, + * because it's OK to occasionally make the wrong decision here, + * and grabbing the lock results in massive lock contention. + */ if (refcount_count(&dbuf_cache_size) > dbuf_cache_max_bytes) { - boolean_t evict_now = B_FALSE; - - mutex_enter(&dbuf_evict_lock); - if (refcount_count(&dbuf_cache_size) > dbuf_cache_max_bytes) { - evict_now = dbuf_cache_above_hiwater(); - cv_signal(&dbuf_evict_cv); - } - mutex_exit(&dbuf_evict_lock); - - if (evict_now) { + if (dbuf_cache_above_hiwater()) dbuf_evict_one(); - } + cv_signal(&dbuf_evict_cv); } } _______________________________________________ svn-src-all@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
