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Date: Tue, 17 Jul 2018 11:54:54 -0700
From: Roman Gushchin <guro@fb.com>
Subject: Re: [PATCH v2 5/7] mm: rename and change semantics of
 nr_indirectly_reclaimable_bytes
Message-ID: <20180717185451.GA18762@castle.DHCP.thefacebook.com>
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To: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Michal Hocko <mhocko@kernel.org>, Johannes Weiner <hannes@cmpxchg.org>, linux-api@vger.kernel.org, Christoph Lameter <cl@linux.com>, David Rientjes <rientjes@google.com>, Mel Gorman <mgorman@techsingularity.net>, Matthew Wilcox <willy@infradead.org>, Vijayanand Jitta <vjitta@codeaurora.org>, Laura Abbott <labbott@redhat.com>, Sumit Semwal <sumit.semwal@linaro.org>

On Tue, Jul 17, 2018 at 10:44:07AM +0200, Vlastimil Babka wrote:
> On 07/02/2018 06:52 PM, Roman Gushchin wrote:
> > On Sat, Jun 30, 2018 at 12:09:27PM +0200, Vlastimil Babka wrote:
> >> On 06/29/2018 11:12 PM, Roman Gushchin wrote:
> >>>>
> >>>> The vmstat counter NR_INDIRECTLY_RECLAIMABLE_BYTES was introduced by commit
> >>>> eb59254608bc ("mm: introduce NR_INDIRECTLY_RECLAIMABLE_BYTES") with the goal of
> >>>> accounting objects that can be reclaimed, but cannot be allocated via a
> >>>> SLAB_RECLAIM_ACCOUNT cache. This is now possible via kmalloc() with
> >>>> __GFP_RECLAIMABLE flag, and the dcache external names user is converted.
> >>>>
> >>>> The counter is however still useful for accounting direct page allocations
> >>>> (i.e. not slab) with a shrinker, such as the ION page pool. So keep it, and:
> >>>
> >>> Btw, it looks like I've another example of usefulness of this counter:
> >>> dynamic per-cpu data.
> >>
> >> Hmm, but are those reclaimable? Most likely not in general? Do you have
> >> examples that are?
> > 
> > If these per-cpu data is something like per-cpu refcounters,
> > which are using to manage reclaimable objects (e.g. cgroup css objects).
> > Of course, they are not always reclaimable, but in certain states.
> 
> BTW, seems you seem interested, could you provide some more formal
> review as well? Others too. We don't need to cover all use cases
> immediately, when the patchset is apparently stalled due to lack of
> review. Thanks!

Sure!

The patchset looks sane at a first glance, but I need some time
to dig deeper. Is v2 the final version?

Thanks!