[Bugs] [Bug 1385226] arbiter volume write performance is bad with sharding

[bugzilla at redhat.com]

https://bugzilla.redhat.com/show_bug.cgi?id=1385226



--- Comment #2 from Worker Ant <bugzilla-bot at gluster.org> ---
COMMIT: http://review.gluster.org/15649 committed in release-3.7 by Pranith
Kumar Karampuri (pkarampu at redhat.com) 
------
commit 7f8916364ff2092e0391b294051dc76764ff02fc
Author: Ravishankar N <ravishankar at redhat.com>
Date:   Fri Oct 14 16:09:08 2016 +0530

    afr: Take full locks in arbiter only for data transactions

    Problem:
    Sharding exposed a bug in arbiter config. where `dd` throughput was
    extremely slow. Shard xlator was sending a fxattrop to update the file
    size immediately after a writev. Arbiter was incorrectly over-riding the
    LLONGMAX-1 start offset (for metadata domain locks) for this fxattrop,
    causing the inodelk to be taken on the data domain. And since the
    preceeding writev hadn't released the lock (afr does a 'lazy'
    unlock if write succeeds on all bricks), this degraded to a blocking
    lock causing extra lock/unlock calls and delays.

    Fix:
    Modify flock.l_len and flock.l_start to take full locks only for data
    transactions.

    > Reviewed-on: http://review.gluster.org/15641
    > Smoke: Gluster Build System <jenkins at build.gluster.org>
    > NetBSD-regression: NetBSD Build System <jenkins at build.gluster.org>
    > CentOS-regression: Gluster Build System <jenkins at build.gluster.org>
    > Reviewed-by: Pranith Kumar Karampuri <pkarampu at redhat.com>
    (cherry picked from commit 3a97486d7f9d0db51abcb13dcd3bc9db935e3a60)

    Change-Id: I906895da2f2d16813607e6c906cb4defb21d7c3b
    BUG: 1385226
    Signed-off-by: Ravishankar N <ravishankar at redhat.com>
    Reported-by: Max Raba <max.raba at comsysto.com>
    Reviewed-on: http://review.gluster.org/15649
    Smoke: Gluster Build System <jenkins at build.gluster.org>
    NetBSD-regression: NetBSD Build System <jenkins at build.gluster.org>
    CentOS-regression: Gluster Build System <jenkins at build.gluster.org>
    Reviewed-by: Pranith Kumar Karampuri <pkarampu at redhat.com>

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