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[2003:d9:9740:fc00:bf68:310a:7021:7923]) by smtp.googlemail.com with ESMTPSA id p23-20020a056402045700b0044792480994sm3611258edw.68.2022.09.03.12.35.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 03 Sep 2022 12:35:13 -0700 (PDT) Message-ID: Date: Sat, 3 Sep 2022 21:35:11 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.2.0 Subject: Re: [PATCH] ipc/msg.c: mitigate the lock contention with percpu counter To: Jiebin Sun , akpm@linux-foundation.org, vasily.averin@linux.dev, shakeelb@google.com, dennis@kernel.org, tj@kernel.org, cl@linux.com, ebiederm@xmission.com, legion@kernel.org, alexander.mikhalitsyn@virtuozzo.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: tim.c.chen@intel.com, feng.tang@intel.com, ying.huang@intel.com, tianyou.li@intel.com, wangyang.guo@intel.com References: <20220902152243.479592-1-jiebin.sun@intel.com> Content-Language: en-US From: Manfred Spraul In-Reply-To: <20220902152243.479592-1-jiebin.sun@intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1662233715; a=rsa-sha256; cv=none; b=QhTWg4Xci74Q0bLHcFAl0hdU5Ww3KI6fO9reA1wxbHH/gvxAnyLcEvJ00ERjR6vwbfcKrr QJzWo9jV/ijc5JI+XEqE4MgOz+IO7zp13cu2YTVXBFlB0X+26M2zx3FQEsfz0WQ5fTVu2r bqabGjU6XqSI4n7EQAggIboOGppk2B4= ARC-Authentication-Results: i=1; imf29.hostedemail.com; dkim=pass header.d=colorfullife-com.20210112.gappssmtp.com header.s=20210112 header.b=aw2e7015; spf=pass (imf29.hostedemail.com: domain of manfred@colorfullife.com designates 209.85.208.46 as permitted sender) smtp.mailfrom=manfred@colorfullife.com; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1662233715; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=SZHgv5PGtCOBVjWnaY9l+4AtXRMYbHOX4QK5lq24Xw8=; b=WMLRd8qxh8o3JvH5Tig0FFIWpRJhyHKxs4NCE/vVvGhVJTuqSkGWpzh2bejDSYdgi8GYwG mLypTWNMwk7prjWRQjYYVd7Npgoa20Mo/WhovJ0GaS35lM+ZSHje5Zp3YA9ZAvQ95UIa7K y2A/yKoyApnoubpFKCb4/Wd8+M5pMuU= X-Stat-Signature: 7hm6837g1xiragowe87t95ork7a8bkda X-Rspamd-Queue-Id: 38F98120094 X-Rspam-User: Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=colorfullife-com.20210112.gappssmtp.com header.s=20210112 header.b=aw2e7015; spf=pass (imf29.hostedemail.com: domain of manfred@colorfullife.com designates 209.85.208.46 as permitted sender) smtp.mailfrom=manfred@colorfullife.com; dmarc=none X-Rspamd-Server: rspam01 X-HE-Tag: 1662233715-989445 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: Hi Jiebin, On 9/2/22 17:22, Jiebin Sun wrote: > The msg_bytes and msg_hdrs atomic counters are frequently > updated when IPC msg queue is in heavy use, causing heavy > cache bounce and overhead. Change them to percpu_counters > greatly improve the performance. Since there is one unique > ipc namespace, additional memory cost is minimal. With ipc namespaces, there is one struct per namespace, correct? The cost is probably still ok, but the change log should be correct. > @@ -1303,14 +1305,16 @@ void msg_init_ns(struct ipc_namespace *ns) > ns->msg_ctlmnb = MSGMNB; > ns->msg_ctlmni = MSGMNI; > > - atomic_set(&ns->msg_bytes, 0); > - atomic_set(&ns->msg_hdrs, 0); > + percpu_counter_init(&ns->percpu_msg_bytes, 0, GFP_KERNEL); > + percpu_counter_init(&ns->percpu_msg_hdrs, 0, GFP_KERNEL); > ipc_init_ids(&ns->ids[IPC_MSG_IDS]); These calls can fail. You must add error handling. --     Manfred