[Lustre-discuss] Lustre write performances 4 times faster after removing SD_IOSTATS from kernel

[Charland, Denis]

> The sd_iostats code uses spin_lock_irqsave() to ensure consistent data structure access in interrupt context, so
> possibly this is causing the performance impact.  The impact might be more severe if there are many cores on the server.

Thanks Andreas, that's a more realistic explanation...

> The sd_iostats patch is completely optional, and is no longer in the RHEL6 kernel patch series in the Lustre
> 2.1/2.2 releases.

It has also been removed from SLES11 kernel patch series in Lustre 1.8.7 release but for another reason (Bugzilla - Bug #23988).

Cheers, Denis