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Bug #9691

fat zap should prefetch when iterating

Added by Brad Lewis about 1 year ago. Updated 7 months ago.

Status:
Closed
Priority:
Normal
Assignee:
Category:
-
Start date:
2018-08-01
Due date:
% Done:

100%

Estimated time:
Difficulty:
Medium
Tags:
needs-triage

Description

When iterating over a ZAP object, we're almost always certain to iterate over the entire object. If there are multiple leaf blocks, we can realize a performance win by issuing reads for all the leaf blocks in parallel when the iteration begins.

For example, if we have 10,000 snapshots, "zfs destroy -nv pool/fs@1%9999" can take 30 minutes when the cache is cold. This change provides a >3x performance improvement, by issuing the reads for all ~64 blocks of each ZAP object in parallel.

History

#1

Updated by Electric Monk 7 months ago

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

git commit 52abb70e073c2a88808c0d66fd810ba8c5080572

commit  52abb70e073c2a88808c0d66fd810ba8c5080572
Author: Matthew Ahrens <mahrens@delphix.com>
Date:   2019-02-25T22:00:05.000Z

    9691 fat zap should prefetch when iterating
    Reviewed by: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com>
    Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
    Reviewed by: George Wilson <george.wilson@delphix.com>
    Approved by: Robert Mustacchi <rm@joyent.com>

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