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([2600:1700:e72:80a0:91f9:c820:22ba:fec7]) by smtp.gmail.com with ESMTPSA id h13sm13112258qtn.26.2021.04.05.14.02.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 05 Apr 2021 14:02:53 -0700 (PDT) Subject: Re: [PATCH] [GSOC] ref-filter: use single strbuf for all output To: ZheNing Hu via GitGitGadget , git@vger.kernel.org Cc: Jeff King , Junio C Hamano , Christian Couder , Hariom Verma , ZheNing Hu References: From: Derrick Stolee Message-ID: <50fce64e-d3f5-05e6-5e2a-645864211176@gmail.com> Date: Mon, 5 Apr 2021 17:02:53 -0400 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On 4/5/2021 10:01 AM, ZheNing Hu via GitGitGadget wrote: > From: ZheNing Hu > > When we use `git for-each-ref`, every ref will call > `show_ref_array_item()` and allocate its own final strbuf > and error strbuf. Instead, we can provide two single strbuf: > final_buf and error_buf that get reused for each output. s/two single strbuf/two buffers/ > When run it 100 times: > > $ git for-each-ref > > on git.git : > > 3.19s user > 3.88s system > 35% cpu > 20.199 total > > to: > > 2.89s user > 4.00s system > 34% cpu > 19.741 total > > The performance has been slightly improved. This is a nice amount of time! Perhaps simplify the presentation: The performance for 'git for-each-ref' on the Git repository itself with X references changes from 3.2 seconds to 2.9 seconds. > Signed-off-by: ZheNing Hu > --- > [GSOC] ref-filter: use single strbuf for all output > > This patch learned Jeff King's optimization measures in git > cat-file(79ed0a5): using a single strbuf for all objects output Instead > of allocating a large number of small strbuf for every object. This part of the cover letter could be put into the commit message itself. Use the correct formatting, though: This approach is similar to the one used by 79ed0a5 (cat-file: use a single strbuf for all output, 2018-08-14) to speed up the cat-file builtin. I found the code change to be correct. Thanks! -Stolee