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bh=iAggmlF4GOtadtjvHCG9VGU8bit4Xaqy/p0gnj0OK7A=; b=RK+XbcmgSb5r0n5e5pwKRqGg012gVMCB/BgpEJ1uGLd83kk2Qp9m3ltJOqPkP9HdoV71ij yD8r+HWyxD3FQY7E1msXK+iv/WfYD+Up/+IJfn6AOg6PMsYPTZNikWOPOYu8mVyvx/r+GO 7shQ7ft20DZTe/p/FIvp82rBcJfEwGA= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 594EA138E3; Tue, 14 Feb 2023 15:56:53 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id Xb8+FEWv62PSAQAAMHmgww (envelope-from ); Tue, 14 Feb 2023 15:56:53 +0000 Date: Tue, 14 Feb 2023 16:56:52 +0100 From: Michal Hocko To: Haifeng Xu Cc: hannes@cmpxchg.org, shakeelb@google.com, muchun.song@linux.dev, akpm@linux-foundation.org, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/memcg: Skip high limit check in root memcg Message-ID: References: <20230210094550.5125-1-haifeng.xu@shopee.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230210094550.5125-1-haifeng.xu@shopee.com> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: F3C8B4000F X-Stat-Signature: 59jxocsur61hfgp6e3n7wak4cmtnz5bx X-Rspam-User: X-HE-Tag: 1676390214-586977 X-HE-Meta: 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 mTAdP+cV REFjmSuhE+iDwRk34L/pUkI/HlYd5hub8R40CIH/YMdB30fh6jusi4EBhWUtyRbMhzX2uBRa6IzIbPwarJ48PgdMyUtEe+SYpBJgWJCuHyOBVFuj2cDPaLdgviYtvWzupvLqQxsN/MoLEwi17GfhGN7L7Ps2EwMA+bc9ckiCMta1MF4J3JInR16ngTdoZ0E4xn31NoG4u1VjzEIZ0qXgVaItLgtcogWBFFBjB 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 10-02-23 09:45:50, Haifeng Xu wrote: > The high limit checks the memory usage from given memcg to root memcg. > However, there is no limit in root memcg. So this check makes no sense > and we can ignore it. Is this check actually addining any benefit? Have you measured aby performance gains by this change? > Signed-off-by: Haifeng Xu > --- > mm/memcontrol.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 73afff8062f9..a31a56598f29 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -2780,6 +2780,10 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask, > do { > bool mem_high, swap_high; > > + /* There is no need for root memcg to check high limit */ > + if (mem_cgroup_is_root(memcg)) > + break; > + > mem_high = page_counter_read(&memcg->memory) > > READ_ONCE(memcg->memory.high); > swap_high = page_counter_read(&memcg->swap) > > -- > 2.25.1 -- Michal Hocko SUSE Labs