lkml.org 
[lkml]   [2016]   [Mar]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 6/6] writeback: throttle buffered writeback
From
Date
On 03/22/2016 02:12 PM, Jeff Moyer wrote:
> Hi, Jens,
>
> Jens Axboe <axboe@fb.com> writes:
>
>> If the device has write back caching, 'wb_cache_delay' delays by
>> this amount of usecs when a write completes before allowing more.
>
> What's the reason behind that?

For classic write back caching, the cache can absorb a bunch of writes
shortly, which means that the completion cost only shows a small part of
the overall cost. This means that if we just throttle on completion,
then when the device starts committing to media, then we'll end up
starving other IO anyway. This knob is a way to attempt to tame that.

--
Jens Axboe

\
 
 \ /
  Last update: 2016-03-22 21:41    [W:0.071 / U:0.168 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site