From nobody Mon Apr 6 00:23:34 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E144BC6FA82 for ; Tue, 13 Sep 2022 11:07:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231889AbiIMLHR (ORCPT ); Tue, 13 Sep 2022 07:07:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51886 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231886AbiIMLHG (ORCPT ); Tue, 13 Sep 2022 07:07:06 -0400 Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 662C05F9A3 for ; Tue, 13 Sep 2022 04:06:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1663067216; x=1694603216; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=MiEDfww/B/2De+3MVM2YwC08RnmErrMIpkB17KjlA6Y=; b=Y5yjog+L8vTo3owYBw8Eob7QTbPIHQpdBw6ao1ZMOL0pybaL359rl5mR FRFPH1FHrMwQFQ9lUYZIixboV5U0LolUDo/GL7XqnHfBh4ujsOHcylsRb qAMekPV3Qp8ADJ2tSnvaYcoc1YmxSFsMgFdrq1+D7Rg9B7H6IShq1SPoK r72WTmKI6LBapT3us6qbTzkaGj5UWcf3SaPIfOjeQkQ3qlDkhFR6PxJvH 2E/dYB/PodtVRMFkEPHCtgQdQHznNvTt3XJTjikRuhoTzmn/Xhdd3cQQW oOfYqOPyHC/Jx6C3vSBnNdvaM3M/03RopBajF0kcY1/NkfU4ncPoHuzFq g==; X-IronPort-AV: E=McAfee;i="6500,9779,10468"; a="285130178" X-IronPort-AV: E=Sophos;i="5.93,312,1654585200"; d="scan'208";a="285130178" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Sep 2022 04:06:55 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.93,312,1654585200"; d="scan'208";a="678522192" Received: from linux-pnp-server-13.sh.intel.com ([10.239.176.176]) by fmsmga008.fm.intel.com with ESMTP; 13 Sep 2022 04:06:50 -0700 From: Jiebin Sun To: 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, manfred@colorfullife.com, 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, jiebin.sun@intel.com, Tim Chen , kernel test robot Subject: [PATCH v6 1/2] percpu: Add percpu_counter_add_local and percpu_counter_sub_local Date: Wed, 14 Sep 2022 03:25:37 +0800 Message-Id: <20220913192538.3023708-2-jiebin.sun@intel.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20220913192538.3023708-1-jiebin.sun@intel.com> References: <20220902152243.479592-1-jiebin.sun@intel.com> <20220913192538.3023708-1-jiebin.sun@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" The batch size in percpu_counter_add_batch should be very large in heavy writing and rare reading case. Add the "_local" version, and mostly it will do local adding, reduce the global updating and mitigate lock contention in writing. Signed-off-by: Jiebin Sun Reviewed-by: Tim Chen Reported-by: kernel test robot --- include/linux/percpu_counter.h | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) diff --git a/include/linux/percpu_counter.h b/include/linux/percpu_counter.h index 01861eebed79..8ed5fba6d156 100644 --- a/include/linux/percpu_counter.h +++ b/include/linux/percpu_counter.h @@ -15,6 +15,9 @@ #include #include =20 +/* percpu_counter batch for local add or sub */ +#define PERCPU_COUNTER_LOCAL_BATCH INT_MAX + #ifdef CONFIG_SMP =20 struct percpu_counter { @@ -56,6 +59,22 @@ static inline void percpu_counter_add(struct percpu_coun= ter *fbc, s64 amount) percpu_counter_add_batch(fbc, amount, percpu_counter_batch); } =20 +/* + * With percpu_counter_add_local() and percpu_counter_sub_local(), counts + * are accumulated in local per cpu counter and not in fbc->count until + * local count overflows PERCPU_COUNTER_LOCAL_BATCH. This makes counter + * write efficient. + * But percpu_counter_sum(), instead of percpu_counter_read(), needs to be + * used to add up the counts from each CPU to account for all the local + * counts. So percpu_counter_add_local() and percpu_counter_sub_local() + * should be used when a counter is updated frequently and read rarely. + */ +static inline void +percpu_counter_add_local(struct percpu_counter *fbc, s64 amount) +{ + percpu_counter_add_batch(fbc, amount, PERCPU_COUNTER_LOCAL_BATCH); +} + static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc) { s64 ret =3D __percpu_counter_sum(fbc); @@ -138,6 +157,13 @@ percpu_counter_add(struct percpu_counter *fbc, s64 amo= unt) preempt_enable(); } =20 +/* non-SMP percpu_counter_add_local is the same with percpu_counter_add */ +static inline void +percpu_counter_add_local(struct percpu_counter *fbc, s64 amount) +{ + percpu_counter_add(fbc, amount); +} + static inline void percpu_counter_add_batch(struct percpu_counter *fbc, s64 amount, s32 batch) { @@ -193,4 +219,10 @@ static inline void percpu_counter_sub(struct percpu_co= unter *fbc, s64 amount) percpu_counter_add(fbc, -amount); } =20 +static inline void +percpu_counter_sub_local(struct percpu_counter *fbc, s64 amount) +{ + percpu_counter_add_local(fbc, -amount); +} + #endif /* _LINUX_PERCPU_COUNTER_H */ --=20 2.31.1