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Fri, 10 May 2024 13:26:46 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id rS1BApYgPmaMBAAAD6G6ig (envelope-from ); Fri, 10 May 2024 13:26:46 +0000 Date: Fri, 10 May 2024 15:26:35 +0200 From: Michal Hocko To: Roman Gushchin Cc: Andrew Morton , Muchun Song , Johannes Weiner , Shakeel Butt , Matthew Wilcox , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH rfc 6/9] mm: memcg: move cgroup v1 oom handling code into memcontrol-v1.c Message-ID: References: <20240509034138.2207186-1-roman.gushchin@linux.dev> <20240509034138.2207186-7-roman.gushchin@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240509034138.2207186-7-roman.gushchin@linux.dev> X-Rspamd-Queue-Id: 7CCA620007 X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: zfqsu9wt844pg5afyw4ujis5xf4ps8yu X-HE-Tag: 1715347609-808280 X-HE-Meta: U2FsdGVkX192sQedKcm+DE3Gy6eIoy/baEc3XCMjIJ8wkVnRIvXf90FrJZSOxP6M/Mo7NDZ8QOxZbJUo48oIw9B+6Mzlzj/DyRdOwUD0qhI2sMoQQbpVThyy/PaCRDdAz7efshHK3B6iN4PjHHUiDiuXIxDNJPO/t0jd/Ml79aJTIbif1jXUbmZ86HEp7JhtZRcLcq58CLHyx+jqsfdyZM9F8naXtk6pmNg7tk0kalV0KjBP21b0AXO2sGWuai4FIWP14BVZO/9X69ifbS9O/rPhIZlhBM7+Vl+aFOfHqIKeoz+hrcDZLN4/2DDjtdsaIolvdbOSknK22nCIeQhBGuPvudfey1bNTU+sXoGD9PBKrnPPYjaaLVlt/RIfXzbBHYEM9vf1uazorEFkKO15G3XBPcdJIx/chBn2LAsUjo3L0FC5JiuH7hn+203GBGfzWh90Tq36BvZuQMNs0h/vY/ntsuu66zFBTS1Hqou4p+ZD+tagyJzN1rktbx3Ptr/zKk2hss9CRmOs150qbm8ALZVHxMBWlh/yFwLhX2De/YD5hWb1UfhG4q9mdoq80gQgzyLeURDNWGn6xUNpGQydwBLlpLNjSt1U2fojfNHYBtFGL91n2SYw5kqJ17rFn99rQcCoq8RITakWWAJ3NjJzv0q7yg5nlTXjlfRWFBY7zT6PBWgNXCsIC8QbSH8BBSiwj02mRQHVH4GLQCgvoPMSjXGqzvO3Gbp5MrSLqy+So4b9VTNY2DbcnGwS+Z5Ilc7A9rcvlwB+bQNxbvUWWmNCU+GftjOODe/ZVX2JTJmmxKCe3J8EWTJ/3io8fELcW5XtDDqhpRKUHx7k51El16RkH10KJYe97u0LadMzhwtmj+42sA5O75bAy7tTYOWb32pZPT51Q1hHXMeC3PjdBRHzYSja+CbD0TT1oB7tRMyA6iKgJ2TlVo6Yfuq/UzzfwfHTrUxxHWuvvywpnRm6IP0 lyglzFNh qkcA+6ixKN1Nfrk5OLchypqYFftBWP5h2rLhOIMLuK3XwlQPngyZY4ayydW4xt5bu4vP4/LZVBxD7huqtRfU2RmL6/wZLOyFKSwhUjDY4l/Fo85+XImxWVNUJwG9Jsp4KU7iiQhokYDjB4TEslzZsG3yIv6Q885T386ieLCkeJQzAUaNHARB8DwB6PV1OL5WwAz/P6grLZU1gS1TDmub+QJaWCg== 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: List-Subscribe: List-Unsubscribe: On Wed 08-05-24 20:41:35, Roman Gushchin wrote: [...] > @@ -1747,106 +1623,14 @@ static bool mem_cgroup_oom(struct mem_cgroup *memcg, gfp_t mask, int order) > > memcg_memory_event(memcg, MEMCG_OOM); > > - /* > - * We are in the middle of the charge context here, so we > - * don't want to block when potentially sitting on a callstack > - * that holds all kinds of filesystem and mm locks. > - * > - * cgroup1 allows disabling the OOM killer and waiting for outside > - * handling until the charge can succeed; remember the context and put > - * the task to sleep at the end of the page fault when all locks are > - * released. > - * > - * On the other hand, in-kernel OOM killer allows for an async victim > - * memory reclaim (oom_reaper) and that means that we are not solely > - * relying on the oom victim to make a forward progress and we can > - * invoke the oom killer here. > - * > - * Please note that mem_cgroup_out_of_memory might fail to find a > - * victim and then we have to bail out from the charge path. > - */ > - if (READ_ONCE(memcg->oom_kill_disable)) { > - if (current->in_user_fault) { > - css_get(&memcg->css); > - current->memcg_in_oom = memcg; > - current->memcg_oom_gfp_mask = mask; > - current->memcg_oom_order = order; > - } > + if (!mem_cgroup_v1_oom_prepare(memcg, mask, order, &locked)) > return false; > - } > - > - mem_cgroup_mark_under_oom(memcg); > - > - locked = mem_cgroup_oom_trylock(memcg); This really confused me because this looks like the oom locking is removed for v2 but this is not the case because mem_cgroup_v1_oom_prepare is not really v1 only code - in other words this is not going to be just return false for CONFIG_MEMCG_V1=n. It makes sense to move the userspace oom handling out to the v1 file. I would keep mem_cgroup_mark_under_oom here. I am not sure about the oom locking thing because I think we can make it v1 only. For v2 I guess we can go without this locking as the oom path is already locked and it implements overkilling prevention (oom_evaluate_task) as it walks all processes in the oom hierarchy. > - > - if (locked) > - mem_cgroup_oom_notify(memcg); > - > - mem_cgroup_unmark_under_oom(memcg); > ret = mem_cgroup_out_of_memory(memcg, mask, order); > - > - if (locked) > - mem_cgroup_oom_unlock(memcg); > + mem_cgroup_v1_oom_finish(memcg, &locked); > > return ret; > } -- Michal Hocko SUSE Labs