linux-kernel - Re: [PATCH 1/3] mm: introduce NR_INDIRECTLY_RECLAIMABLE

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Date:   Wed, 25 Apr 2018 13:52:12 +0100
From:   Roman Gushchin <guro@...com>
To:     Vijayanand Jitta <vjitta@...eaurora.org>
CC:     vinayak menon <vinayakm.list@...il.com>,
        Vlastimil Babka <vbabka@...e.cz>, <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Michal Hocko <mhocko@...e.com>,
        Johannes Weiner <hannes@...xchg.org>,
        <linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <kernel-team@...com>, Linux API <linux-api@...r.kernel.org>
Subject: Re: [PATCH 1/3] mm: introduce NR_INDIRECTLY_RECLAIMABLE_BYTES

On Wed, Apr 25, 2018 at 09:19:29AM +0530, Vijayanand Jitta wrote:
> >>>> Idk, I don't like the idea of adding a counter outside of the vm counters
> >>>> infrastructure, and I definitely wouldn't touch the exposed
> >>>> nr_slab_reclaimable and nr_slab_unreclaimable fields.
> >>>
> >>> We would be just making the reported values more precise wrt reality.
> >>
> >> It depends on if we believe that only slab memory can be reclaimable
> >> or not. If yes, this is true, otherwise not.
> >>
> >> My guess is that some drivers (e.g. networking) might have buffers,
> >> which are reclaimable under mempressure, and are allocated using
> >> the page allocator. But I have to look closer...
> >>
> > 
> > One such case I have encountered is that of the ION page pool. The page pool
> > registers a shrinker. When not in any memory pressure page pool can go high
> > and thus cause an mmap to fail when OVERCOMMIT_GUESS is set. I can send
> > a patch to account ION page pool pages in NR_INDIRECTLY_RECLAIMABLE_BYTES.

Perfect!
This is exactly what I've expected.

> > 
> > Thanks,
> > Vinayak
> > 
> 
> As Vinayak mentioned NR_INDIRECTLY_RECLAIMABLE_BYTES can be used to solve the issue
> with ION page pool when OVERCOMMIT_GUESS is set, the patch for the same can be 
> found here https://lkml.org/lkml/2018/4/24/1288

This makes perfect sense to me.

Please, fell free to add:
Acked-by: Roman Gushchin <guro@...com>

Thank you!