[Bugs] [Bug 1426045] New: poor fio rand read performance

[bugzilla at redhat.com]

https://bugzilla.redhat.com/show_bug.cgi?id=1426045

            Bug ID: 1426045
           Summary: poor fio rand read performance
           Product: Red Hat Gluster Storage
           Version: 3.2
         Component: read-ahead
          Assignee: rgowdapp at redhat.com
          Reporter: csaba at redhat.com
        QA Contact: rhinduja at redhat.com
                CC: bugs at gluster.org, hchen at redhat.com,
                    rgowdapp at redhat.com, rhs-bugs at redhat.com
        Depends On: 1094328
            Blocks: 845300



+++ This bug was initially created as a clone of Bug #1094328 +++

Description of problem:

Turning on read-ahead results in poor random read performance from fio

Version-Release number of selected component (if applicable):

3.4

How reproducible:


Steps to Reproduce:
1. Turn on read-ahead 
gluster volume set vol performance.read-ahead-page-count 16

2. Run fio random read workload
fio --rw=randread --bs=1m --size=4g --runtime=30 --numjobs=1 --group_reporting
--name=/8 --ioengine=gfapi --volume=vol --brick=bd-vm  

The throughput is 186MB/s


Actual results:

Turning off read ahead and run the workload again, I get 350MB/s

Expected results:

Read-ahead should not slow down random read performance.

Additional info:

--- Additional comment from Anand Avati on 2014-05-05 12:23:08 EDT ---

REVIEW: http://review.gluster.org/7676 (add option to 1) keep readahead for
straddle read; 2) disable readahead otherwise) posted (#1) for review on master
by Huamin Chen (hchen at redhat.com)

--- Additional comment from Anand Avati on 2014-05-29 11:36:31 EDT ---

REVIEW: http://review.gluster.org/7676 (add option to 1) keep readahead for
straddle read; 2) disable readahead otherwise) posted (#2) for review on master
by Huamin Chen (hchen at redhat.com)

--- Additional comment from Anand Avati on 2014-05-29 11:36:38 EDT ---

REVIEW: http://review.gluster.org/7927 (response to Jeff Darcy's review. 1)
change tuning param name to performance.read-ahead-enable-even-noncontiguous.
When set to 1, read-ahead is enabled even for noncontiguous IO; when set to 0
(default), read-ahead is disabled when noncontiguity is detected. 2) the end of
file offset is conditionally set) posted (#1) for review on master by Huamin
Chen (hchen at redhat.com)

--- Additional comment from Anand Avati on 2014-06-02 15:55:00 EDT ---

REVIEW: http://review.gluster.org/7676 (add option to 1) keep readahead for
straddle read; 2) disable readahead otherwise) posted (#3) for review on master
by Huamin Chen (hchen at redhat.com)

--- Additional comment from Anand Avati on 2014-06-02 15:59:16 EDT ---

REVIEW: http://review.gluster.org/7958 (response to Jeff Darcy's review. 1)
change tuning param name to performance.read-ahead-enable-even-noncontiguous.
When set to 1, read-ahead is enabled even for noncontiguous IO; when set to 0
(default), read-ahead is disabled when noncontiguity is detected. 2) the end of
file offset is conditionally set) posted (#1) for review on master by Huamin
Chen (hchen at redhat.com)

--- Additional comment from Anand Avati on 2014-06-02 16:25:31 EDT ---

REVIEW: http://review.gluster.org/7676 (add option to 1) keep readahead for
straddle read; 2) disable readahead otherwise) posted (#4) for review on master
by Huamin Chen (hchen at redhat.com)

--- Additional comment from Anand Avati on 2015-05-28 04:35:10 EDT ---

REVIEW: http://review.gluster.org/7676 (add option to 1) keep readahead for
straddle read; 2) disable readahead otherwise) posted (#6) for review on master
by Raghavendra G (rgowdapp at redhat.com)

--- Additional comment from Mike McCune on 2016-03-28 19:25:37 EDT ---

This bug was accidentally moved from POST to MODIFIED via an error in
automation, please see mmccune at redhat.com with any questions


Referenced Bugs:

https://bugzilla.redhat.com/show_bug.cgi?id=1094328
[Bug 1094328] poor fio rand read performance
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