linux-kernel - Re: [PATCH v2 5/7] mm: rename and change semantics of nr_indirectly_reclaimable

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Date:   Fri, 29 Jun 2018 14:12:05 -0700
From:   Roman Gushchin <guro@...com>
To:     Vlastimil Babka <vbabka@...e.cz>
CC:     kbuild test robot <lkp@...el.com>, <kbuild-all@...org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        <linux-api@...r.kernel.org>, Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Matthew Wilcox <willy@...radead.org>,
        Vijayanand Jitta <vjitta@...eaurora.org>,
        Laura Abbott <labbott@...hat.com>,
        Sumit Semwal <sumit.semwal@...aro.org>
Subject: Re: [PATCH v2 5/7] mm: rename and change semantics of
 nr_indirectly_reclaimable_bytes

On Fri, Jun 29, 2018 at 05:37:02PM +0200, Vlastimil Babka wrote:
> On 06/20/2018 01:23 PM, kbuild test robot wrote:
> > Hi Vlastimil,
> > 
> > Thank you for the patch! Yet something to improve:
> > 
> > [auto build test ERROR on mmotm/master]
> > [also build test ERROR on v4.18-rc1 next-20180619]
> > [if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
> > 
> > url:    https://github.com/0day-ci/linux/commits/Vlastimil-Babka/kmalloc-reclaimable-caches/20180618-172912
> > base:   git://git.cmpxchg.org/linux-mmotm.git master
> > config: x86_64-allmodconfig (attached as .config)
> > compiler: gcc-7 (Debian 7.3.0-16) 7.3.0
> > reproduce:
> >         # save the attached .config to linux build tree
> >         make ARCH=x86_64 
> > 
> > All errors (new ones prefixed by >>):
> > 
> >    drivers/staging//android/ion/ion_page_pool.c: In function 'ion_page_pool_remove':
> >>> drivers/staging//android/ion/ion_page_pool.c:56:40: error: 'NR_INDIRECTLY_RECLAIMABLE_BYTES' undeclared (first use in this function)
> >      mod_node_page_state(page_pgdat(page), NR_INDIRECTLY_RECLAIMABLE_BYTES,
> >                                            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >    drivers/staging//android/ion/ion_page_pool.c:56:40: note: each undeclared identifier is reported only once for each function it appears in
> > 
> > vim +/NR_INDIRECTLY_RECLAIMABLE_BYTES +56 drivers/staging//android/ion/ion_page_pool.c
> 
> Looks like I missed a hunk, updated patch below.
> 
> ----8<----
> From a0053c64c72d7e094252d0d7462de8569d87c543 Mon Sep 17 00:00:00 2001
> From: Vlastimil Babka <vbabka@...e.cz>
> Date: Tue, 22 May 2018 16:10:10 +0200
> Subject: [PATCH v3 5/7] mm: rename and change semantics of
>  nr_indirectly_reclaimable_bytes
> 
> 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.