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s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=H/4ytESJPTv0Fk+cvfD+ZeYMt6Is89WPN3CMnUvmQxM=; b=tc2qLPBjdTc/kwx701ziuYrQF/cQIiJQiou7+ORSsbYLNIvEn6Lbm+hr3VsuqePYKx RJa6/HLVjxttjp5KpTOcgeXInokqOqTnhqSJjvR+P3tovpqkp6iJcPi0PX8w5GMA9sv2 X+dl0vrM/OZeRm2bV2BpQ/ancQzSxsq7Qf2/iIdHCuh1/31VwgWwRHKK0uOs7vhrH2if 0KiGMYgDl+l9xzNMdTDE/wWr88fwZWXpVG2wMAfGLEFvtTmVjJfkcBI5k5yLEl6Pt+At FgilBIvz7jqWfb5+c6reafSJlPC37FX5UZcHf8bt/HT/5QvkdRc5dcQn1PSrviuSZNsR 0Xwg== X-Gm-Message-State: AOAM530PHW6LwOMnkIQPGS802sqBRxZ+YBWcdy8uXuDupqlCKCVYT/Ka wOj2E8+KkDwSwugznzyQ+P4S9lBK+4bDuP11Tl8N1g== X-Google-Smtp-Source: ABdhPJwYD6TFySTm5cYZmtRpAi8UMNhwXWW0cMMBEcQZMDvs2E75z8IPDt6LpAAGJhJXuTsXYwe6n4eEC09LOVn2Ey4= X-Received: by 2002:a19:4301:: with SMTP id q1mr3056210lfa.96.1592605015159; Fri, 19 Jun 2020 15:16:55 -0700 (PDT) MIME-Version: 1.0 References: <20200608230654.828134-1-guro@fb.com> <20200608230654.828134-7-guro@fb.com> <20200619213810.GA237539@carbon.dhcp.thefacebook.com> In-Reply-To: <20200619213810.GA237539@carbon.dhcp.thefacebook.com> From: Shakeel Butt Date: Fri, 19 Jun 2020 15:16:44 -0700 Message-ID: Subject: Re: [PATCH v6 06/19] mm: memcg/slab: obj_cgroup API To: Roman Gushchin Cc: Andrew Morton , Christoph Lameter , Johannes Weiner , Michal Hocko , Linux MM , Vlastimil Babka , Kernel Team , LKML Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 593D6180C07A3 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam04 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Jun 19, 2020 at 2:38 PM Roman Gushchin wrote: > [snip] > > > memcg->objcg is rcu protected. > > > objcg->memcg is a raw pointer, which is always pointing at a memory > > > cgroup, but can be atomically swapped to the parent memory cgroup. So > > > the caller > > > > What type of caller? The allocator? > > Basically whoever uses the pointer. Is it better to s/caller/user? > Yes 'user' feels better. > > [...] > > > > The normal stock can go to 32*nr_cpus*PAGE_SIZE. I am wondering if > > just PAGE_SIZE is too less for obj stock. > > It works on top of the current stock of 32 pages, so it can grab these > 32 pages without any atomic operations. And it should be easy to increase > this limit if we'll see any benefits. > > Thank you for looking into the patchset! > > Andrew, can you, please, squash the following fix based on Shakeel's suggestions? > Thanks! > > -- For the following squashed into the original patch: Reviewed-by: Shakeel Butt > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > index 7ed3af71a6fb..2499f78cf32d 100644 > --- a/include/linux/memcontrol.h > +++ b/include/linux/memcontrol.h > @@ -326,7 +326,7 @@ struct mem_cgroup { > int kmemcg_id; > enum memcg_kmem_state kmem_state; > struct obj_cgroup __rcu *objcg; > - struct list_head objcg_list; > + struct list_head objcg_list; /* list of inherited objcgs */ > #endif > > #ifdef CONFIG_CGROUP_WRITEBACK > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 70cd44b28db1..9f14b91700d9 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -2843,7 +2843,7 @@ __always_inline struct obj_cgroup *get_obj_cgroup_from_current(void) > struct obj_cgroup *objcg = NULL; > struct mem_cgroup *memcg; > > - if (unlikely(!current->mm)) > + if (unlikely(!current->mm && !current->active_memcg)) > return NULL; > > rcu_read_lock();