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Date:   Sat, 18 Jul 2020 10:24:49 -0700
From:   Guenter Roeck <linux@roeck-us.net>
To:     Roman Gushchin <guro@fb.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Christoph Lameter <cl@linux.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Michal Hocko <mhocko@kernel.org>,
        Shakeel Butt <shakeelb@google.com>, linux-mm@kvack.org,
        Vlastimil Babka <vbabka@suse.cz>, kernel-team@fb.com,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v7 17/19] mm: memcg/slab: use a single set of kmem_caches
 for all allocations
Message-ID: <20200718172449.GA48060@roeck-us.net>
References: <20200623174037.3951353-1-guro@fb.com>
 <20200623174037.3951353-18-guro@fb.com>
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On Tue, Jun 23, 2020 at 10:40:35AM -0700, Roman Gushchin wrote:
> Instead of having two sets of kmem_caches: one for system-wide and
> non-accounted allocations and the second one shared by all accounted
> allocations, we can use just one.
> 
> The idea is simple: space for obj_cgroup metadata can be allocated on
> demand and filled only for accounted allocations.
> 
> It allows to remove a bunch of code which is required to handle kmem_cache
> clones for accounted allocations.  There is no more need to create them,
> accumulate statistics, propagate attributes, etc.  It's a quite
> significant simplification.
> 
> Also, because the total number of slab_caches is reduced almost twice (not
> all kmem_caches have a memcg clone), some additional memory savings are
> expected.  On my devvm it additionally saves about 3.5% of slab memory.
> 
> Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
> Signed-off-by: Roman Gushchin <guro@fb.com>
> Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
> Reviewed-by: Shakeel Butt <shakeelb@google.com>

This patch results in:

{standard input}: Assembler messages:
{standard input}:140: Warning: macro instruction expanded into multiple instructions
mm/slub.c: In function 'slab_alloc.constprop':
mm/slub.c:2897:30: error: inlining failed in call to always_inline 'slab_alloc.constprop': recursive inlining
 static __always_inline void *slab_alloc(struct kmem_cache *s,

and many similar messages when trying to build mips:64r6el_defconfig
or mips:defconfig. Bisect log attached.

Guenter

---

# bad: [aab7ee9f8ff0110bfcd594b33dc33748dc1baf46] Add linux-next specific files for 20200717
# good: [11ba468877bb23f28956a35e896356252d63c983] Linux 5.8-rc5
git bisect start 'HEAD' 'v5.8-rc5'
# good: [4d55a7a1298d197755c1a0f4512f56917e938a83] Merge remote-tracking branch 'crypto/master'
git bisect good 4d55a7a1298d197755c1a0f4512f56917e938a83
# good: [e63bf5dcce255302e355cb2277a3a39c83752c92] Merge remote-tracking branch 'devicetree/for-next'
git bisect good e63bf5dcce255302e355cb2277a3a39c83752c92
# good: [94d932ec3afb923efd8c736974f8316413175a5b] Merge remote-tracking branch 'thunderbolt/next'
git bisect good 94d932ec3afb923efd8c736974f8316413175a5b
# good: [5ddd2e0dbe8fceb80b0b36bd38a32217be7a04a5] Merge remote-tracking branch 'livepatching/for-next'
git bisect good 5ddd2e0dbe8fceb80b0b36bd38a32217be7a04a5
# bad: [40346f79983caf46fb92f779b0353422d43580a9] ipc/shm.c: Remove the superfluous break
git bisect bad 40346f79983caf46fb92f779b0353422d43580a9
# bad: [0b917599517f71ddef5f7274a8199a33cecd49b2] kasan: update required compiler versions in documentation
git bisect bad 0b917599517f71ddef5f7274a8199a33cecd49b2
# good: [7822c5f77725d5bf4ea48f155b0aa3827db19423] tmpfs: per-superblock i_ino support
git bisect good 7822c5f77725d5bf4ea48f155b0aa3827db19423
# bad: [c5b15b89803e3ed2810be285def5f4836e5ee629] mm, memcg: reclaim more aggressively before high allocator throttling
git bisect bad c5b15b89803e3ed2810be285def5f4836e5ee629
# good: [2b6d98a0b0cb5ff828228c6a094813c4919727da] mm: memcg/slab: remove redundant check in memcg_accumulate_slabinfo()
git bisect good 2b6d98a0b0cb5ff828228c6a094813c4919727da
# bad: [d32b702628530c68b4147d410b4cdf21610e9f93] mm: memcg/percpu: per-memcg percpu memory statistics
git bisect bad d32b702628530c68b4147d410b4cdf21610e9f93
# bad: [b109396be9be1b8fd91fa4c70bd73a0e93722274] percpu: return number of released bytes from pcpu_free_area()
git bisect bad b109396be9be1b8fd91fa4c70bd73a0e93722274
# bad: [6cee58aca5d334ee8195a711e4eb61a05e5f7eb5] kselftests: cgroup: add kernel memory accounting tests
git bisect bad 6cee58aca5d334ee8195a711e4eb61a05e5f7eb5
# bad: [2528f5d4f3c139035dc3adcbfb6c63ca14c840f0] mm: memcg/slab: use a single set of kmem_caches for all allocations
git bisect bad 2528f5d4f3c139035dc3adcbfb6c63ca14c840f0
# first bad commit: [2528f5d4f3c139035dc3adcbfb6c63ca14c840f0] mm: memcg/slab: use a single set of kmem_caches for all allocations