From: Johannes Weiner <hannes@cmpxchg.org>
To: Roman Gushchin <guro@fb.com>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
Michal Hocko <mhocko@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Kernel Team <Kernel-team@fb.com>,
Shakeel Butt <shakeelb@google.com>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
Waiman Long <longman@redhat.com>,
Christoph Lameter <cl@linux.com>
Subject: Re: [PATCH 09/16] mm: memcg/slab: charge individual slab objects instead of pages
Date: Thu, 31 Oct 2019 10:41:51 -0400 [thread overview]
Message-ID: <20191031144151.GB1168@cmpxchg.org> (raw)
In-Reply-To: <20191031015238.GA21323@castle.DHCP.thefacebook.com>
On Thu, Oct 31, 2019 at 01:52:44AM +0000, Roman Gushchin wrote:
> On Fri, Oct 25, 2019 at 03:41:18PM -0400, Johannes Weiner wrote:
> > @@ -3117,15 +3095,24 @@ void __memcg_kmem_uncharge(struct page *page, int order)
> > css_put_many(&memcg->css, nr_pages);
> > }
> >
> > -int __memcg_kmem_charge_subpage(struct mem_cgroup *memcg, size_t size,
> > - gfp_t gfp)
> > +int obj_cgroup_charge(struct obj_cgroup *objcg, size_t size, gfp_t gfp)
> > {
> > - return try_charge(memcg, gfp, size, true);
> > + int ret;
> > +
> > + if (consume_obj_stock(objcg, nr_bytes))
> > + return 0;
> > +
> > + ret = try_charge(objcg->memcg, gfp, 1);
> > + if (ret)
> > + return ret;
> The second problem is also here. If a task belonging to a different memcg
> is scheduled on this cpu, most likely we will need to refill both stocks,
> even if we need only a small temporarily allocation.
Yes, that's a good thing. The reason we have the per-cpu caches in the
first place is because most likely the same cgroup will perform
several allocations. Both the slab allocator and the page allocator
have per-cpu caches for the same reason. I don't really understand
what the argument is.
> > +
> > + refill_obj_stock(objcg, PAGE_SIZE - size);
>
> And the third problem is here. Percpu allocations (on which accounting I'm
> working right now) can be larger than a page.
How about this?
nr_pages = round_up(size, PAGE_SIZE);
try_charge(objcg->memcg, nr_pages);
refill_obj_stock(objcg, size % PAGE_SIZE);
> This is fairly small issue in comparison to the first one. But it illustrates
> well the main point: we can't simple get a page from the existing API and
> sublease it in parts. The problem is that we need to break the main principle
> that a page belongs to a single memcg.
We can change the underlying assumptions of the existing API if they
are no longer correct. We don't have to invent a parallel stack.
next prev parent reply other threads:[~2019-10-31 14:41 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-18 0:28 [PATCH 00/16] The new slab memory controller Roman Gushchin
2019-10-18 0:28 ` [PATCH 01/16] mm: memcg: introduce mem_cgroup_ptr Roman Gushchin
2019-10-18 0:28 ` [PATCH 02/16] mm: vmstat: use s32 for vm_node_stat_diff in struct per_cpu_nodestat Roman Gushchin
2019-10-20 22:44 ` Christopher Lameter
2019-10-21 1:15 ` Roman Gushchin
2019-10-21 18:09 ` Christopher Lameter
2019-10-20 22:51 ` Christopher Lameter
2019-10-21 1:21 ` Roman Gushchin
2019-10-18 0:28 ` [PATCH 03/16] mm: vmstat: convert slab vmstat counter to bytes Roman Gushchin
2019-10-18 0:28 ` [PATCH 04/16] mm: memcg/slab: allocate space for memcg ownership data for non-root slabs Roman Gushchin
2019-10-18 0:28 ` [PATCH 05/16] mm: slub: implement SLUB version of obj_to_index() Roman Gushchin
2019-10-18 0:28 ` [PATCH 06/16] mm: memcg/slab: save memcg ownership data for non-root slab objects Roman Gushchin
2019-10-18 0:28 ` [PATCH 07/16] mm: memcg: move memcg_kmem_bypass() to memcontrol.h Roman Gushchin
2019-10-18 0:28 ` [PATCH 08/16] mm: memcg: introduce __mod_lruvec_memcg_state() Roman Gushchin
2019-10-18 0:28 ` [PATCH 09/16] mm: memcg/slab: charge individual slab objects instead of pages Roman Gushchin
2019-10-25 19:41 ` Johannes Weiner
2019-10-25 20:00 ` Roman Gushchin
2019-10-25 20:52 ` Johannes Weiner
2019-10-31 1:52 ` Roman Gushchin
2019-10-31 14:23 ` Johannes Weiner
2019-10-31 14:41 ` Johannes Weiner [this message]
2019-10-31 15:07 ` Roman Gushchin
2019-10-31 18:50 ` Johannes Weiner
2019-10-18 0:28 ` [PATCH 10/16] mm: memcg: move get_mem_cgroup_from_current() to memcontrol.h Roman Gushchin
2019-10-18 0:28 ` [PATCH 11/16] mm: memcg/slab: replace memcg_from_slab_page() with memcg_from_slab_obj() Roman Gushchin
2019-10-18 0:28 ` [PATCH 13/16] mm: memcg/slab: deprecate memory.kmem.slabinfo Roman Gushchin
2019-10-18 0:28 ` [PATCH 14/16] mm: memcg/slab: use one set of kmem_caches for all memory cgroups Roman Gushchin
2019-10-18 0:28 ` [PATCH 15/16] tools/cgroup: make slabinfo.py compatible with new slab controller Roman Gushchin
2019-10-18 0:28 ` [PATCH 16/16] mm: slab: remove redundant check in memcg_accumulate_slabinfo() Roman Gushchin
2019-10-18 17:03 ` [PATCH 00/16] The new slab memory controller Waiman Long
2019-10-18 17:12 ` Roman Gushchin
2019-10-22 13:22 ` Michal Hocko
2019-10-22 13:28 ` Michal Hocko
2019-10-22 15:48 ` Roman Gushchin
2019-10-22 13:31 ` Michal Hocko
2019-10-22 15:59 ` Roman Gushchin
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