linux-kernel - Re: [RFC PATCH 0/5] kmalloc-reclaimable caches

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Date:   Thu, 24 May 2018 13:13:52 +0100
From:   Roman Gushchin <guro@...com>
To:     Vlastimil Babka <vbabka@...e.cz>
CC:     <linux-mm@...ck.org>, Michal Hocko <mhocko@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        <linux-kernel@...r.kernel.org>, <linux-api@...r.kernel.org>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Vijayanand Jitta <vjitta@...eaurora.org>
Subject: Re: [RFC PATCH 0/5] kmalloc-reclaimable caches

On Thu, May 24, 2018 at 01:00:06PM +0200, Vlastimil Babka wrote:
> Hi,
> 
> as discussed at LSF/MM [1] here's a RFC patchset that introduces
> kmalloc-reclaimable caches (more details in the first patch) and uses them
> for SLAB freelists and dcache external names. The latter allows us to
> repurpose the NR_INDIRECTLY_RECLAIMABLE_BYTES counter later in the series.
> 
> This is how /proc/slabinfo looks like after booting in virtme:
> 
> ...
> kmalloc-reclaimable-4194304      0      0 4194304    1 1024 : tunables    1    1    0 : slabdata      0      0      0
> ...
> kmalloc-reclaimable-96     17     64    128   32    1 : tunables  120   60    8 : slabdata      2      2      0
> kmalloc-reclaimable-64     50    128     64   64    1 : tunables  120   60    8 : slabdata      2      2      6
> kmalloc-reclaimable-32      0      0     32  124    1 : tunables  120   60    8 : slabdata      0      0      0
> kmalloc-4194304        0      0 4194304    1 1024 : tunables    1    1    0 : slabdata      0      0      0
> ...
> kmalloc-64          2888   2944     64   64    1 : tunables  120   60    8 : slabdata     46     46    454
> kmalloc-32          4325   4712     32  124    1 : tunables  120   60    8 : slabdata     38     38    563
> kmalloc-128         1178   1216    128   32    1 : tunables  120   60    8 : slabdata     38     38    114
> ...
> 
> /proc/vmstat with new/renamed nr_reclaimable counter (patch 4):
> 
> ...
> nr_slab_reclaimable 2817
> nr_slab_unreclaimable 1781
> ...
> nr_reclaimable 2817
> ...
> 
> /proc/meminfo with exposed nr_reclaimable counter (patch 5):
> 
> ...
> AnonPages:          8624 kB
> Mapped:             3340 kB
> Shmem:               564 kB
> Reclaimable:       11272 kB
> Slab:              18368 kB
> SReclaimable:      11272 kB
> SUnreclaim:         7096 kB
> KernelStack:        1168 kB
> PageTables:          448 kB
> ...
> 
> Now for the issues a.k.a. why RFC:
> 
> - I haven't find any other obvious users for reclaimable kmalloc (yet)

As I remember, ION memory allocator was discussed related to this theme:
https://lkml.org/lkml/2018/4/24/1288

> I did a superset as IIRC somebody suggested that in the older threads or at LSF.

This looks nice to me!

Thanks!