Author: avg Date: Fri May 26 11:30:55 2017 New Revision: 318928 URL: https://svnweb.freebsd.org/changeset/base/318928
Log: MFV r318927: 8025 dbuf_read() creates unnecessary zio_root() for bonus buf illumos/illumos-gate@def4fac5882b4ca67bd0f4a53509b6d1fa8ae14e https://github.com/illumos/illumos-gate/commit/def4fac5882b4ca67bd0f4a53509b6d1fa8ae14e https://www.illumos.org/issues/8025 dbuf_read() creates a zio_root() to track and wait for all the zio's that may happen as part of this call. However, if the blkptr_t for this buffer is NULL or a hole, we will not create any more zio's, so this zio_root() is unnecessary. This is always the case when calling dbuf_read() on a bonus buffer, because it has no blkptr (it's part of the containing dnode). For workloads that read a lot of bonus buffers (e.g. file creation and removal), creating and destroying these unnecessary zio's can decrease performance by around 3%. Reviewed by: Dan Kimmel <[email protected]> Reviewed by: Pavel Zakharov <[email protected]> Reviewed by: Prashanth Sreenivasa <[email protected]> Approved by: Robert Mustacchi <[email protected]> Author: Matthew Ahrens <[email protected]> Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dbuf.c Directory Properties: head/sys/cddl/contrib/opensolaris/ (props changed) Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dbuf.c ============================================================================== --- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dbuf.c Fri May 26 11:29:31 2017 (r318927) +++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dbuf.c Fri May 26 11:30:55 2017 (r318928) @@ -1088,7 +1088,6 @@ int dbuf_read(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags) { int err = 0; - boolean_t havepzio = (zio != NULL); boolean_t prefetch; dnode_t *dn; @@ -1132,9 +1131,13 @@ dbuf_read(dmu_buf_impl_t *db, zio_t *zio DB_DNODE_EXIT(db); } else if (db->db_state == DB_UNCACHED) { spa_t *spa = dn->dn_objset->os_spa; + boolean_t need_wait = B_FALSE; - if (zio == NULL) + if (zio == NULL && + db->db_blkptr != NULL && !BP_IS_HOLE(db->db_blkptr)) { zio = zio_root(spa, NULL, NULL, ZIO_FLAG_CANFAIL); + need_wait = B_TRUE; + } dbuf_read_impl(db, zio, flags); /* dbuf_read_impl has dropped db_mtx for us */ @@ -1146,7 +1149,7 @@ dbuf_read(dmu_buf_impl_t *db, zio_t *zio rw_exit(&dn->dn_struct_rwlock); DB_DNODE_EXIT(db); - if (!havepzio) + if (need_wait) err = zio_wait(zio); } else { /* @@ -1181,7 +1184,6 @@ dbuf_read(dmu_buf_impl_t *db, zio_t *zio mutex_exit(&db->db_mtx); } - ASSERT(err || havepzio || db->db_state == DB_CACHED); return (err); } _______________________________________________ [email protected] mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "[email protected]"
