From: Johannes Weiner <hannes@cmpxchg.org>
To: Roman Gushchin <guro@fb.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Christoph Lameter <cl@linux.com>,
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 v4 06/19] mm: memcg/slab: obj_cgroup API
Date: Wed, 27 May 2020 15:56:14 -0400 [thread overview]
Message-ID: <20200527195614.GC47905@cmpxchg.org> (raw)
In-Reply-To: <20200526214227.989341-7-guro@fb.com>
On Tue, May 26, 2020 at 02:42:14PM -0700, Roman Gushchin wrote:
> @@ -257,6 +257,98 @@ struct cgroup_subsys_state *vmpressure_to_css(struct vmpressure *vmpr)
> }
>
> #ifdef CONFIG_MEMCG_KMEM
> +extern spinlock_t css_set_lock;
> +
> +static void obj_cgroup_release(struct percpu_ref *ref)
> +{
> + struct obj_cgroup *objcg = container_of(ref, struct obj_cgroup, refcnt);
> + struct mem_cgroup *memcg;
> + unsigned int nr_bytes;
> + unsigned int nr_pages;
> + unsigned long flags;
> +
> + /*
> + * At this point all allocated objects are freed, and
> + * objcg->nr_charged_bytes can't have an arbitrary byte value.
> + * However, it can be PAGE_SIZE or (x * PAGE_SIZE).
> + *
> + * The following sequence can lead to it:
> + * 1) CPU0: objcg == stock->cached_objcg
> + * 2) CPU1: we do a small allocation (e.g. 92 bytes),
> + * PAGE_SIZE bytes are charged
> + * 3) CPU1: a process from another memcg is allocating something,
> + * the stock if flushed,
> + * objcg->nr_charged_bytes = PAGE_SIZE - 92
> + * 5) CPU0: we do release this object,
> + * 92 bytes are added to stock->nr_bytes
> + * 6) CPU0: stock is flushed,
> + * 92 bytes are added to objcg->nr_charged_bytes
> + *
> + * In the result, nr_charged_bytes == PAGE_SIZE.
> + * This page will be uncharged in obj_cgroup_release().
> + */
Thanks for adding this.
> +int obj_cgroup_charge(struct obj_cgroup *objcg, gfp_t gfp, size_t size)
> +{
> + struct mem_cgroup *memcg;
> + unsigned int nr_pages, nr_bytes;
> + int ret;
> +
> + if (consume_obj_stock(objcg, size))
> + return 0;
> +
> + rcu_read_lock();
> + memcg = obj_cgroup_memcg(objcg);
> + css_get(&memcg->css);
> + rcu_read_unlock();
Can you please also add the comment here I mentioned last time? To
explain why we're not checking objcg->nr_charged_bytes if we have
already pre-allocated bytes that could satisfy the allocation.
Otherwise, looks good to me.
next prev parent reply other threads:[~2020-05-27 19:56 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-26 21:42 [PATCH v4 00/19] The new cgroup slab memory controller Roman Gushchin
2020-05-26 21:42 ` [PATCH v4 01/19] mm: memcg: factor out memcg- and lruvec-level changes out of __mod_lruvec_state() Roman Gushchin
2020-05-26 21:42 ` [PATCH v4 02/19] mm: memcg: prepare for byte-sized vmstat items Roman Gushchin
2020-05-26 21:42 ` [PATCH v4 03/19] mm: memcg: convert vmstat slab counters to bytes Roman Gushchin
2020-05-27 11:43 ` Vlastimil Babka
2020-05-27 16:25 ` Roman Gushchin
2020-05-26 21:42 ` [PATCH v4 04/19] mm: slub: implement SLUB version of obj_to_index() Roman Gushchin
2020-05-27 19:44 ` Johannes Weiner
2020-05-26 21:42 ` [PATCH v4 05/19] mm: memcontrol: decouple reference counting from page accounting Roman Gushchin
2020-05-26 21:42 ` [PATCH v4 06/19] mm: memcg/slab: obj_cgroup API Roman Gushchin
2020-05-27 19:56 ` Johannes Weiner [this message]
2020-05-27 20:03 ` Roman Gushchin
2020-05-26 21:42 ` [PATCH v4 07/19] mm: memcg/slab: allocate obj_cgroups for non-root slab pages Roman Gushchin
2020-05-26 21:42 ` [PATCH v4 08/19] mm: memcg/slab: save obj_cgroup for non-root slab objects Roman Gushchin
2020-05-26 21:42 ` [PATCH v4 09/19] mm: memcg/slab: charge individual slab objects instead of pages Roman Gushchin
2020-05-26 21:42 ` [PATCH v4 10/19] mm: memcg/slab: deprecate memory.kmem.slabinfo Roman Gushchin
2020-05-27 15:54 ` Vlastimil Babka
2020-05-27 16:28 ` Roman Gushchin
2020-05-26 21:42 ` [PATCH v4 11/19] mm: memcg/slab: move memcg_kmem_bypass() to memcontrol.h Roman Gushchin
2020-05-26 21:42 ` [PATCH v4 12/19] mm: memcg/slab: use a single set of kmem_caches for all accounted allocations Roman Gushchin
2020-05-27 16:01 ` Vlastimil Babka
2020-05-27 16:29 ` Roman Gushchin
2020-05-26 21:42 ` [PATCH v4 13/19] mm: memcg/slab: simplify memcg cache creation Roman Gushchin
2020-05-26 21:42 ` [PATCH v4 14/19] mm: memcg/slab: remove memcg_kmem_get_cache() Roman Gushchin
2020-05-26 21:42 ` [PATCH v4 15/19] mm: memcg/slab: deprecate slab_root_caches Roman Gushchin
2020-05-26 21:42 ` [PATCH v4 16/19] mm: memcg/slab: remove redundant check in memcg_accumulate_slabinfo() Roman Gushchin
2020-05-26 21:42 ` [PATCH v4 17/19] mm: memcg/slab: use a single set of kmem_caches for all allocations Roman Gushchin
2020-05-26 21:42 ` [PATCH v4 18/19] kselftests: cgroup: add kernel memory accounting tests Roman Gushchin
2020-05-26 21:42 ` [PATCH v4 19/19] tools/cgroup: add memcg_slabinfo.py tool Roman Gushchin
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