linux-kernel - Re: [PATCH 3/3] dcache: account external names as indirectly reclaimable memory

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Message-ID: <20180416114144.GK17484@dhcp22.suse.cz>
Date:   Mon, 16 Apr 2018 13:41:44 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Johannes Weiner <hannes@...xchg.org>
Cc:     Vlastimil Babka <vbabka@...e.cz>, Minchan Kim <minchan@...nel.org>,
        Roman Gushchin <guro@...com>, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...com
Subject: Re: [PATCH 3/3] dcache: account external names as indirectly
 reclaimable memory

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.

-- 
Michal Hocko
SUSE Labs