[Bugs] [Bug 1438706] New: Sharding: Fix a performance bug

[bugzilla at redhat.com]

https://bugzilla.redhat.com/show_bug.cgi?id=1438706

            Bug ID: 1438706
           Summary: Sharding: Fix a performance bug
           Product: Red Hat Gluster Storage
           Version: 3.2
         Component: sharding
          Keywords: Triaged
          Assignee: kdhananj at redhat.com
          Reporter: amukherj at redhat.com
        QA Contact: knarra at redhat.com
                CC: bugs at gluster.org, kdhananj at redhat.com,
                    rhs-bugs at redhat.com, storage-qa-internal at redhat.com
        Depends On: 1436739
            Blocks: 1437326, 1437330



+++ This bug was initially created as a clone of Bug #1436739 +++

Description of problem:

As per Sanjay Rao's inputs, there was a performance drop in random reads fio
workload when run through vms hosted on sharded volumes.

Volume profile indicated a big difference between the number of lookups sent by
FUSE and number of lookups received by individual bricks.

Through code reading, it was found that there is a performance bug in shard
which was causing the translator to trigger unusually high number of lookups
for cache invalidation even when there was no modification to the file.


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


How reproducible:


Steps to Reproduce:
1.
2.
3.

Actual results:


Expected results:


Additional info:

--- Additional comment from Worker Ant on 2017-03-28 10:23:33 EDT ---

REVIEW: https://review.gluster.org/16961 (features/shard: Pass the correct iatt
for cache invalidation) posted (#1) for review on master by Krutika Dhananjay
(kdhananj at redhat.com)

--- Additional comment from Worker Ant on 2017-03-30 01:48:38 EDT ---

REVIEW: https://review.gluster.org/16961 (features/shard: Pass the correct iatt
for cache invalidation) posted (#2) for review on master by Krutika Dhananjay
(kdhananj at redhat.com)

--- Additional comment from Worker Ant on 2017-03-30 02:15:59 EDT ---

COMMIT: https://review.gluster.org/16961 committed in master by Pranith Kumar
Karampuri (pkarampu at redhat.com) 
------
commit dd5ada1f11d76b4c55c7c55d23718617f11a6c12
Author: Krutika Dhananjay <kdhananj at redhat.com>
Date:   Tue Mar 28 19:26:41 2017 +0530

    features/shard: Pass the correct iatt for cache invalidation

    This fixes a performance issue with shard which was causing
    the translator to trigger unusually high number of lookups
    for cache invalidation even when there was no modification to
    the file.

    In shard_common_stat_cbk(), it is local->prebuf that contains the
    aggregated size and block count as opposed to buf which only holds the
    attributes for the physical copy of base shard. Passing buf for
    inode_ctx invalidation would always set refresh to true since the file
    size in inode ctx contains the aggregated size and would never be same
    as @buf->ia_size. This was leading to every write/read being preceded
    by a lookup on the base shard even when the file underwent no
    modification.

    Change-Id: Ib0349291d2d01f3782d6d0bdd90c6db5e0609210
    BUG: 1436739
    Signed-off-by: Krutika Dhananjay <kdhananj at redhat.com>
    Reviewed-on: https://review.gluster.org/16961
    NetBSD-regression: NetBSD Build System <jenkins at build.gluster.org>
    CentOS-regression: Gluster Build System <jenkins at build.gluster.org>
    Smoke: Gluster Build System <jenkins at build.gluster.org>
    Reviewed-by: Pranith Kumar Karampuri <pkarampu at redhat.com>


Referenced Bugs:

https://bugzilla.redhat.com/show_bug.cgi?id=1436739
[Bug 1436739] Sharding: Fix a performance bug
https://bugzilla.redhat.com/show_bug.cgi?id=1437326
[Bug 1437326] Sharding: Fix a performance bug
https://bugzilla.redhat.com/show_bug.cgi?id=1437330
[Bug 1437330] Sharding: Fix a performance bug
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