[Bugs] [Bug 1601166] performance.read-ahead causes huge increase in unnecessary network traffic

[bugzilla at redhat.com]

https://bugzilla.redhat.com/show_bug.cgi?id=1601166

Raghavendra G <rgowdapp at redhat.com> changed:

           What    |Removed                     |Added
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             Status|NEW                         |ASSIGNED
           Assignee|bugs at gluster.org            |rgowdapp at redhat.com



--- Comment #2 from Raghavendra G <rgowdapp at redhat.com> ---
>From client logs attached to bz 1393419, I could see that reads from kernel are
interspersed with attr calls. These fstat calls flush the read-ahead cache. So,
data is read more than once - once for read-ahead and later when application
actually issues read. This explains the extra data read over network.

>From the same logs, it also looks read-ahead logic is bit aggressive making
this problem more prominent. Had there been no fstat calls from kernel, the
prefetched data would be eventually consumed as cache hit and it would not have
been a problem.

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