[Bugs] [Bug 1335373] cyclic dentry loop in inode table

[bugzilla at redhat.com]

https://bugzilla.redhat.com/show_bug.cgi?id=1335373



--- Comment #6 from Raghavendra G <rgowdapp at redhat.com> ---
(In reply to Raghavendra G from comment #5)
> (In reply to Amar Tumballi from comment #4)
> > This can be resolved by `gluster volume set $VOL features.sdfs enable` (the
> > above patch finally made it to repo).
> 
> But doesn't enabling sdfs regresses performance significantly and hence not
> a viable solution? 

commit 829337ed3971a53086f1562d826e79d4f3e3ed39
Author: Amar Tumballi <amarts at redhat.com>
Date:   Mon Jan 28 18:30:24 2019 +0530

    features/sdfs: disable by default

    With the feature enabled, some of the performance testing results,
    specially those which create millions of small files, got approximately
    4x regression compared to version before enabling this.

    On master without this patch:  765 creates/sec
    On master with this patch   : 3380 creates/sec

    Also there seems to be regression caused by this in 'ls -l' workload.

    On master without this patch:  3030 files/sec
    On master with this patch   : 16610 files/sec

    This is a feature added to handle multiple clients parallely operating
    (specially those which race for file creates with same name) on a single
    namespace/directory. Considering that is < 3% of Gluster's usecase right
    now, it makes sense to disable the feature by default, so we don't
    penalize the default users who doesn't bother about this usecase.
    Also note that the client side translators, specially, distribute,
    replicate and disperse already handle the issue upto 99.5% of the cases
    without SDFS, so it makes sense to keep the feature disabled by default.

    Credits: Shyamsunder <srangana at redhat.com> for running the tests and
    getting the numbers.

    Change-Id: Iec49ce1d82e621e9db25eb633fcb1d932e74f4fc
    Updates: bz#1670031
    Signed-off-by: Amar Tumballi <amarts at redhat.com>

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