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Message-ID: <c14415f18273d134665819bb0d43b1c99b88030c.camel@linux.intel.com>
Subject: Re: [PATCH v5 2/2] ipc/msg: mitigate the lock contention with
 percpu counter
From:   Tim Chen <tim.c.chen@linux.intel.com>
To:     Jiebin Sun <jiebin.sun@intel.com>, 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
Date:   Fri, 09 Sep 2022 09:11:16 -0700
In-Reply-To: <20220909203636.2652466-3-jiebin.sun@intel.com>
References: <20220902152243.479592-1-jiebin.sun@intel.com>
         <20220909203636.2652466-1-jiebin.sun@intel.com>
         <20220909203636.2652466-3-jiebin.sun@intel.com>
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On Sat, 2022-09-10 at 04:36 +0800, 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_counter
> greatly improve the performance. Since there is one percpu
> struct per namespace, additional memory cost is minimal.
> Reading of the count done in msgctl call, which is infrequent.
> So the need to sum up the counts in each CPU is infrequent.
> 
> Apply the patch and test the pts/stress-ng-1.4.0
> -- system v message passing (160 threads).
> 
> Score gain: 3.99x
> 
> CPU: ICX 8380 x 2 sockets
> Core number: 40 x 2 physical cores
> Benchmark: pts/stress-ng-1.4.0
> -- system v message passing (160 threads)

Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com>

> 
> Signed-off-by: Jiebin Sun <jiebin.sun@intel.com>
> ---
>