Re: Warning on memory offline (and possible in usual migration?)

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

On Tue, 15 Apr 2008 12:31:00 -0700 (PDT)
Christoph Lameter <clameter@sgi.com> wrote:
> Page migration should stop after 10 retries though? You need to set the RC 
> to another value than -EAGAIN in order to avoid the retries.
> 
> if (page_mapping(page) && !PageUptodate(page)) {
> 	rc = -EBUSY;
> 	goto unlock;
> }
> 
> will stop retries.
> 
will try.

> > Once I use drop_caches, memory offlining works very well.
> > (even under some workload.) If the code I added is bad, plz blame me.
> 
> The retries during page migration may hold off the completion of bringing 
> up a page up to date since the PageLock is repeatedly acquired. So either 
> pass more pages in one go to migrate_pages() or pause once in awhile?
> 
yes, *may*.  But page offlining can be stopped by Ctrl-C.

What I experienced was.
==
%echo offline > /sys/device/system/memoryXXXX/state
...wait for a minute
Ctrl-C
% sync
% sync
% echo offline > /sys/device/system/memoryXXXX/state
...wait for a minute
% echo 3 > /proc/sys/vm/drop_caches
% echo offline > /sys/device/system/memoryXXXX/state
success.
==

I'll see what happens wish -EBUSY but maybe no help...

Thanks,
-Kame

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