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[146.241.44.112]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-4635a9eefd0sm3301361cf.27.2024.11.14.01.17.34 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 14 Nov 2024 01:17:35 -0800 (PST) Message-ID: <9e64f1ca-844f-47ec-8555-4ac1e409ec16@redhat.com> Date: Thu, 14 Nov 2024 10:17:32 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] net/core/net-procfs: use seq_put_decimal_ull_width() for decimal values in /proc/net/dev To: David Wang <00107082@163.com>, davem@davemloft.net, edumazet@google.com, kuba@kernel.org Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20241110045221.4959-1-00107082@163.com> Content-Language: en-US From: Paolo Abeni In-Reply-To: <20241110045221.4959-1-00107082@163.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/10/24 05:52, David Wang wrote: > seq_printf() is costy, when reading /proc/net/dev, profiling indicates > about 13% samples of seq_printf(): > dev_seq_show(98.350% 428046/435229) > dev_seq_printf_stats(99.777% 427092/428046) > dev_get_stats(86.121% 367814/427092) > rtl8169_get_stats64(98.519% 362365/367814) > dev_fetch_sw_netstats(0.554% 2038/367814) > loopback_get_stats64(0.250% 919/367814) > dev_get_tstats64(0.077% 284/367814) > netdev_stats_to_stats64(0.051% 189/367814) > _find_next_bit(0.029% 106/367814) > seq_printf(13.719% 58594/427092) > And on a system with one wireless interface, timing for 1 million rounds of > stress reading /proc/net/dev: > real 0m51.828s > user 0m0.225s > sys 0m51.671s > On average, reading /proc/net/dev takes ~0.051ms > > With this patch, extra costs parsing format string by seq_printf() can be > optimized out, and the timing for 1 million rounds of read is: > real 0m49.127s > user 0m0.295s > sys 0m48.552s > On average, ~0.048ms reading /proc/net/dev, a ~6% improvement. > > Even though dev_get_stats() takes up the majority of the reading process, > the improvement is still significant; > And the improvement may vary with the physical interface on the system. > > Signed-off-by: David Wang <00107082@163.com> If the user-space is concerned with performances, it must use netlink. Optimizing a legacy interface gives IMHO a very wrong message. I'm sorry, I think we should not accept this change. /P