K 10 svn:author V 3 avg K 8 svn:date V 27 2017-05-26T11:30:55.757594Z K 7 svn:log V 1064 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 Reviewed by: Pavel Zakharov Reviewed by: Prashanth Sreenivasa Approved by: Robert Mustacchi Author: Matthew Ahrens END