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Mon, 08 Jun 2026 08:04:59 -0700 (PDT) Received: from fedora ([172.245.82.59]) by smtp.gmail.com with ESMTPSA id 00721157ae682-7ea23a9946bsm84389287b3.37.2026.06.08.08.04.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 08 Jun 2026 08:04:58 -0700 (PDT) Date: Mon, 8 Jun 2026 10:04:51 -0500 From: Ming Lei To: wenxiong@linux.ibm.com Cc: linux-block@vger.kernel.org, axboe@kernel.dk, yukuai@fygo.io, wenxiong@us.ibm.com Subject: Re: [PATCH]block: Observing higher CPU utilization during random IO testing Message-ID: References: <20260604162709.3006327-1-wenxiong@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260604162709.3006327-1-wenxiong@linux.ibm.com> On Thu, Jun 04, 2026 at 12:27:09PM -0400, wenxiong@linux.ibm.com wrote: > From: Wen Xiong > > Hi All, > > Our performance team observed the higher CPU utilization in RHEL10 compared > to RHEL9.8, observed the similar issue in upstream kernel(v7.1-rc6) as well > when running FIO random IO tests. Random IO tests are more CPU intensive > than sequential IO tests due to several factors: more context switching, > interrupt Handling, cache Inefficiency etc. > > Given commit 060406c61c7c ("block: add plug while submitting IO") > causes performance regression. This patch reverts it. One thing is that plugging should be applied in outer io code path, also it doesn't make sense to apply this timestamp optimization for single IO batch. > > Below is performance comparison with the latest upstream kernel. > > Iotype qd nj rmix mpstat busy mpstat busy > with inner plug without inner plug > Randrw 1 20 100 53% 24% > Randrw 1 40 100 70% 24% > Randrw 1 20 70 40% 24% > Randrw 1 40 70 60% 26% > Randrw 1 20 0 14% 6% > Randrw 1 40 0 20% 7% > > Signed-off-by: Wen Xiong > Suggested-by: Ming Lei With commit log update, this patch looks fine: Reviewed-by: Ming Lei Thanks, Ming