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([2600:1700:e72:80a0:b51d:31f1:a0d6:7fc2]) by smtp.gmail.com with ESMTPSA id 204sm3261441ioc.50.2021.07.15.07.55.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 15 Jul 2021 07:55:28 -0700 (PDT) Subject: Re: [PATCH v2 6/7] merge-ort: avoid recursing into directories when we don't need to To: Elijah Newren via GitGitGadget , git@vger.kernel.org Cc: =?UTF-8?B?w4Z2YXIgQXJuZmrDtnLDsCBCamFybWFzb24=?= , Elijah Newren References: <3409a6cd631deb361d3ecb94491c0c297c52fb53.1626204784.git.gitgitgadget@gmail.com> From: Derrick Stolee Message-ID: <24c5ef26-f5d3-fb0e-b2da-24cdac90450d@gmail.com> Date: Thu, 15 Jul 2021 10:55:26 -0400 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <3409a6cd631deb361d3ecb94491c0c297c52fb53.1626204784.git.gitgitgadget@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On 7/13/2021 3:33 PM, Elijah Newren via GitGitGadget wrote: > From: Elijah Newren ... > For the testcases mentioned in commit 557ac0350d ("merge-ort: begin > performance work; instrument with trace2_region_* calls", 2020-10-28), > this change improves the performance as follows: > > Before After > no-renames: 5.235 s ± 0.042 s 205.1 ms ± 3.8 ms Wow! This is quite the savings, and reinforces that when no renames exist we are likely to hit this optimization. > mega-renames: 9.419 s ± 0.107 s 1.564 s ± 0.010 s I'm surprised that this one works so well, too. Clearly, there must be a lot of directories that can be skipped despite many renames existing. > just-one-mega: 480.1 ms ± 3.9 ms 479.5 ms ± 3.9 ms And no overhead added to this case. Good. > + /* Loop over the set of paths we need to know rename info for */ > + strset_for_each_entry(&renames->relevant_sources[side], > + &iter, entry) { > + char *rename_target, *dir, *dir_marker; > + struct strmap_entry *e; > + > + /* > + * if we don't know delete/rename info for this path, > + * then we need to recurse into all trees to get all > + * adds to make sure we have it. > + */ super-nit: s/if/If/ Otherwise, I can't speak to the code being 100% correct because this area is so dense. I find the code to be well organized, which will help finding and fixing any potential bugs that might show up in strange corner cases later. Thanks, -Stolee