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Bug #8025

dbuf_read() creates unnecessary zio_root() for bonus buf

Added by Prakash Surya over 2 years ago. Updated over 2 years ago.

Status:
Closed
Priority:
Normal
Assignee:
Category:
zfs - Zettabyte File System
Start date:
2017-04-03
Due date:
% Done:

100%

Estimated time:
Difficulty:
Medium
Tags:
needs-triage

Description

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%.

History

#1

Updated by Electric Monk over 2 years ago

  • % Done changed from 0 to 100
  • Status changed from New to Closed

git commit def4fac5882b4ca67bd0f4a53509b6d1fa8ae14e

commit  def4fac5882b4ca67bd0f4a53509b6d1fa8ae14e
Author: Matthew Ahrens <mahrens@delphix.com>
Date:   2017-04-18T20:12:30.000Z

    8025 dbuf_read() creates unnecessary zio_root() for bonus buf
    Reviewed by: Dan Kimmel <dan.kimmel@delphix.com>
    Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
    Reviewed by: Prashanth Sreenivasa <pks@delphix.com>
    Approved by: Robert Mustacchi <rm@joyent.com>

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