On Thu, Sep 17, 2015 at 3:42 PM, Chris Mason <clm@xxxxxx> wrote:
>
> Playing around with the plug a little, most of the unplugs are coming
> from the cond_resched_lock(). Not really sure why we are doing the
> cond_resched() there, we should be doing it before we retake the lock
> instead.
>
> This patch takes my box (with dirty thresholds at 1.5GB/3GB) from 195K
> files/sec up to 213K. Average IO size is the same as 4.3-rc1.
Ok, so at least for you, part of the problem really ends up being that
there's a mix of the "synchronous" unplugging (by the actual explicit
"blk_finish_plug(&plug);") and the writeback that is handed off to
kblockd_workqueue.
I'm not seeing why that should be an issue. Sure, there's some CPU
overhead to context switching, but I don't see that it should be that
big of a deal.
I wonder if there is something more serious wrong with the kblockd_workqueue.
Linus
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
