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Date: Tue, 17 Apr 2018 12:24:13 +0100
From: Roman Gushchin <guro@fb.com>
To: Michal Hocko <mhocko@kernel.org>
CC: Johannes Weiner <hannes@cmpxchg.org>, Vlastimil Babka <vbabka@suse.cz>,
        Minchan Kim <minchan@kernel.org>, <linux-mm@kvack.org>,
        Andrew Morton
	<akpm@linux-foundation.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        <linux-fsdevel@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <kernel-team@fb.com>
Subject: Re: [PATCH 3/3] dcache: account external names as indirectly
 reclaimable memory
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On Mon, Apr 16, 2018 at 01:41:44PM +0200, Michal Hocko wrote:
> On Fri 13-04-18 10:37:16, Johannes Weiner wrote:
> > On Fri, Apr 13, 2018 at 04:28:21PM +0200, Michal Hocko wrote:
> > > On Fri 13-04-18 16:20:00, Vlastimil Babka wrote:
> > > > We would need kmalloc-reclaimable-X variants. It could be worth it,
> > > > especially if we find more similar usages. I suspect they would be more
> > > > useful than the existing dma-kmalloc-X :)
> > > 
> > > I am still not sure why __GFP_RECLAIMABLE cannot be made work as
> > > expected and account slab pages as SLAB_RECLAIMABLE
> > 
> > Can you outline how this would work without separate caches?
> 
> I thought that the cache would only maintain two sets of slab pages
> depending on the allocation reuquests. I am pretty sure there will be
> other details to iron out and maybe it will turn out that such a large
> portion of the chache would need to duplicate the state that a
> completely new cache would be more reasonable. Is this worth exploring
> at least? I mean something like this should help with the fragmentation
> already AFAIU. Accounting would be just free on top.

IMO, this approach is much better than duplicating all kmalloc caches.
It's definitely has to be explored and discussed.

Thank you!