lkml.org 
[lkml]   [2011]   [Feb]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 0/5] blk-throttle: writeback and swap IO control
On Thu, Feb 24, 2011 at 09:40:39AM +0900, KAMEZAWA Hiroyuki wrote:

[..]
> > > If we don't consider the swap IO, any other IO
> > > operation from our point of view will happen directly from process
> > > context (writes in memory + sync reads from the block device).
> >
> > Why do we need to account for swap IO? Application never asked for swap
> > IO. It is kernel's decision to move soem pages to swap to free up some
> > memory. What's the point in charging those pages to application group
> > and throttle accordingly?
> >
>
> I think swap I/O should be controlled by memcg's dirty_ratio.
> But, IIRC, NEC guy had a requirement for this...
>
> I think some enterprise cusotmer may want to throttle the whole speed of
> swapout I/O (not swapin)...so, they may be glad if they can limit throttle
> the I/O against a disk partition or all I/O tagged as 'swapio' rather than
> some cgroup name.

If swap is on a separate disk, then one can control put write throttling rules
on systemwide swapout. Though I still don't understand how that can help.

>
> But I'm afraid slow swapout may consume much dirty_ratio and make things
> worse ;)

Exactly. So I think focus should be controlling things earlier and stop
applications early before they can either write too much data in page
cache etc.

Thanks
Vivek


\
 
 \ /
  Last update: 2011-02-24 17:23    [W:0.232 / U:0.148 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site