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Re: [PATCH 1/5] mm: vmscan: Do not writeback filesystem pages in direct

To: Mel Gorman <mgorman@xxxxxxx>
Subject: Re: [PATCH 1/5] mm: vmscan: Do not writeback filesystem pages in direct reclaim
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Date: Thu, 14 Jul 2011 15:17:08 +0900
Cc: Linux-MM <linux-mm@xxxxxxxxx>, LKML <linux-kernel@xxxxxxxxxxxxxxx>, XFS <xfs@xxxxxxxxxxx>, Dave Chinner <david@xxxxxxxxxxxxx>, Christoph Hellwig <hch@xxxxxxxxxxxxx>, Johannes Weiner <jweiner@xxxxxxxxxx>, Wu Fengguang <fengguang.wu@xxxxxxxxx>, Jan Kara <jack@xxxxxxx>, Rik van Riel <riel@xxxxxxxxxx>, Minchan Kim <minchan.kim@xxxxxxxxx>
In-reply-to: <20110714061915.GN7529@xxxxxxx>
Organization: FUJITSU Co. LTD.
References: <1310567487-15367-1-git-send-email-mgorman@xxxxxxx> <1310567487-15367-2-git-send-email-mgorman@xxxxxxx> <20110714103801.83e10fdb.kamezawa.hiroyu@xxxxxxxxxxxxxx> <20110714061915.GN7529@xxxxxxx>
On Thu, 14 Jul 2011 07:19:15 +0100
Mel Gorman <mgorman@xxxxxxx> wrote:

> On Thu, Jul 14, 2011 at 10:38:01AM +0900, KAMEZAWA Hiroyuki wrote:
> > > @@ -825,6 +825,15 @@ static unsigned long shrink_page_list(struct 
> > > list_head *page_list,
> > >           if (PageDirty(page)) {
> > >                   nr_dirty++;
> > >  
> > > +                 /*
> > > +                  * Only kswapd can writeback filesystem pages to
> > > +                  * avoid risk of stack overflow
> > > +                  */
> > > +                 if (page_is_file_cache(page) && !current_is_kswapd()) {
> > > +                         inc_zone_page_state(page, NR_VMSCAN_WRITE_SKIP);
> > > +                         goto keep_locked;
> > > +                 }
> > > +
> > 
> > 
> > This will cause tons of memcg OOM kill because we have no help of kswapd 
> > (now).
> > 
> > Could you make this
> > 
> >     if (scanning_global_lru(sc) && page_is_file_cache(page) && 
> > !current_is_kswapd())
> > ...
> > 
> 
> I can, but as Christoph points out, the request is already being
> ignored so how will it help?
> 

Hmm, ok, please go as you do now. I'll do hurry up to implement dirty_ratio by 
myself
without waiting for original patch writer. I think his latest version was really
near to be merged... I'll start rebase his one to mmotm in this end of month.

Thanks,
-Kame

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