lkml.org 
[lkml]   [2013]   [Jun]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] block: Reserve only one queue tag for sync IO if only 3 tags are available
On Fri, Jun 28 2013, Jan Kara wrote:
> In case a device has three tags available we still reserve two of them
> for sync IO. That leaves only a single tag for async IO such as
> writeback from flusher thread which results in poor performance.
>
> Allow async IO to consume two tags in case queue has three tag availabe
> to get a decent async write performance.
>
> This patch improves streaming write performance on a machine with such disk
> from ~21 MB/s to ~52 MB/s. Also postmark throughput in presence of
> streaming writer improves from 8 to 12 transactions per second so sync
> IO doesn't seem to be harmed in presence of heavy async writer.

That's pretty crazy! Never seen a device like that. But yes, it
obviously exists, and the 2 reserved tags doesn't work well for that. So
it's an improvement.

Thanks, will queue up for 3.11.

--
Jens Axboe



\
 
 \ /
  Last update: 2013-06-28 23:01    [W:0.034 / U:2.292 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site