From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 23A64C47082 for ; Tue, 8 Jun 2021 16:12:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0768C6108E for ; Tue, 8 Jun 2021 16:12:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231580AbhFHQOj (ORCPT ); Tue, 8 Jun 2021 12:14:39 -0400 Received: from mail-wr1-f47.google.com ([209.85.221.47]:36672 "EHLO mail-wr1-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231221AbhFHQOj (ORCPT ); Tue, 8 Jun 2021 12:14:39 -0400 Received: by mail-wr1-f47.google.com with SMTP id e11so12001495wrg.3 for ; Tue, 08 Jun 2021 09:12:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=message-id:in-reply-to:references:from:date:subject:mime-version :content-transfer-encoding:fcc:to:cc; bh=EFVbDjK6SqZ0+OxD+Qns6eJAHEOMQW2yiWPKzfdNB6s=; b=LGhLk82XXKn2iL8hkd/u3i5bPEjR+ttmxb1RQUaK84f25WUWKACJ/xLl+YxK+nA9gj Whg9zbvPRAqFfYPMgo4cYY8cKA6TL+5IbK5ZjY3B52vRPQNvxkBvgF1arAR2oe3RCSeq OdL20jnMnADj5K8obVbDDycj4bqjrpyZRLnahnNN1nkkax0by8l2TxegcxF1oKrpiQ73 nJ5nkmXW1oBHSbtxlN7rBn+imqHGbXvziHeqzZMR14lD0ld3meS4EeveDE+ghSleUQ1B FOaiHaYEXMxcOLOHXfd6CoIJLK/0/pVRP61mwKLbpM4d2y/R6Od57fx/2tm+2UgQIxnc buoA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:message-id:in-reply-to:references:from:date :subject:mime-version:content-transfer-encoding:fcc:to:cc; bh=EFVbDjK6SqZ0+OxD+Qns6eJAHEOMQW2yiWPKzfdNB6s=; b=rrr2UfxdiyyonO6rsymirHFF+QJ0T/WBZMRAQGLwG9oW/4AyRQVoK013E0i4RWkXoo fftVW38SYIR2AQvPhBaSSttWdPXONoZmYo2Re/aKyUcgVCRhPv3Ym1ztWaa90nkeYiVD 56l4NQePk18QWD5rdAlhHxENsuJS+u3aoaK1jVCF31+1Rj51QpJKYBhqnLYnQAXfok89 AtYnq6f+GrDSQ9HZHMlvGzcGte1Qwg/v5Fx0cZN3aw78H6C1KhnbDlcHJo0WrSaMhPLj x7Q7NHqVBl8x4tSl4KQgCPDrZveohYhJN0MBg387nJEEiXiKezhvo4xiOYgKbG0scnTT Oinw== X-Gm-Message-State: AOAM533k0up9wIpPQHa37FMDUNr2pglnc8uxMtbQsnq6nZcXdjR6viLZ vtUObMkH1HP/3bdeXgVX0DQhlMYzfFE= X-Google-Smtp-Source: ABdhPJxGHVolyK5rvz6zgMRQ9+Sd7/7TW7rtO2RwRjO/BQ5uIrQCATZCSexKtxQ5E0qGZWLM0HyqrQ== X-Received: by 2002:adf:9dd1:: with SMTP id q17mr23042347wre.402.1623168705206; Tue, 08 Jun 2021 09:11:45 -0700 (PDT) Received: from [127.0.0.1] ([13.74.141.28]) by smtp.gmail.com with ESMTPSA id a11sm20331237wrr.48.2021.06.08.09.11.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Jun 2021 09:11:44 -0700 (PDT) Message-Id: <140c1e89e0ec69c5c5e8a99b632c1cf25c2325d4.1623168703.git.gitgitgadget@gmail.com> In-Reply-To: References: From: "Elijah Newren via GitGitGadget" Date: Tue, 08 Jun 2021 16:11:39 +0000 Subject: [PATCH v4 1/4] merge-ort: replace string_list_df_name_compare with faster alternative MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Fcc: Sent To: git@vger.kernel.org Cc: Derrick Stolee , Jonathan Tan , Taylor Blau , =?UTF-8?Q?Ren=C3=A9?= Scharfe , Elijah Newren , Derrick Stolee , Jeff King , Elijah Newren , Elijah Newren Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org From: Elijah Newren Gathering accumulated times from trace2 output on the mega-renames testcase, I saw the following timings (where I'm only showing a few lines to highlight the portions of interest): 10.120 : label:incore_nonrecursive 4.462 : ..label:process_entries 3.143 : ....label:process_entries setup 2.988 : ......label:plist special sort 1.305 : ....label:processing 2.604 : ..label:collect_merge_info 2.018 : ..label:merge_start 1.018 : ..label:renames In the above output, note that the 4.462 seconds for process_entries was split as 3.143 seconds for "process_entries setup" and 1.305 seconds for "processing" (and a little time for other stuff removed from the highlight). Most of the "process_entries setup" time was spent on "plist special sort" which corresponds to the following code: trace2_region_enter("merge", "plist special sort", opt->repo); plist.cmp = string_list_df_name_compare; string_list_sort(&plist); trace2_region_leave("merge", "plist special sort", opt->repo); In other words, in a merge strategy that would be invoked by passing "-sort" to either rebase or merge, sorting an array takes more time than anything else. Serves me right for naming my merge strategy this way. Rewrite the comparison function in a way that does not require finding out the lengths of the strings when comparing them. While at it, tweak the code for our specific case -- no need to handle a variety of modes, for example. The combination of these changes reduced the time spent in "plist special sort" by ~25% in the mega-renames case. 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: 5.622 s ± 0.059 s 5.235 s ± 0.042 s mega-renames: 10.127 s ± 0.073 s 9.419 s ± 0.107 s just-one-mega: 500.3 ms ± 3.8 ms 480.1 ms ± 3.9 ms Signed-off-by: Elijah Newren Reviewed-by: Derrick Stolee --- merge-ort.c | 67 +++++++++++++++++++++++++++++++++++++---------------- 1 file changed, 47 insertions(+), 20 deletions(-) diff --git a/merge-ort.c b/merge-ort.c index 142d44d74d63..061f15701359 100644 --- a/merge-ort.c +++ b/merge-ort.c @@ -2746,31 +2746,58 @@ static int detect_and_process_renames(struct merge_options *opt, /*** Function Grouping: functions related to process_entries() ***/ -static int string_list_df_name_compare(const char *one, const char *two) +static int sort_dirs_next_to_their_children(const char *one, const char *two) { - int onelen = strlen(one); - int twolen = strlen(two); + unsigned char c1, c2; + /* - * Here we only care that entries for D/F conflicts are - * adjacent, in particular with the file of the D/F conflict - * appearing before files below the corresponding directory. - * The order of the rest of the list is irrelevant for us. + * Here we only care that entries for directories appear adjacent + * to and before files underneath the directory. We can achieve + * that by pretending to add a trailing slash to every file and + * then sorting. In other words, we do not want the natural + * sorting of + * foo + * foo.txt + * foo/bar + * Instead, we want "foo" to sort as though it were "foo/", so that + * we instead get + * foo.txt + * foo + * foo/bar + * To achieve this, we basically implement our own strcmp, except that + * if we get to the end of either string instead of comparing NUL to + * another character, we compare '/' to it. + * + * If this unusual "sort as though '/' were appended" perplexes + * you, perhaps it will help to note that this is not the final + * sort. write_tree() will sort again without the trailing slash + * magic, but just on paths immediately under a given tree. * - * To achieve this, we sort with df_name_compare and provide - * the mode S_IFDIR so that D/F conflicts will sort correctly. - * We use the mode S_IFDIR for everything else for simplicity, - * since in other cases any changes in their order due to - * sorting cause no problems for us. + * The reason to not use df_name_compare directly was that it was + * just too expensive (we don't have the string lengths handy), so + * it was reimplemented. */ - int cmp = df_name_compare(one, onelen, S_IFDIR, - two, twolen, S_IFDIR); + /* - * Now that 'foo' and 'foo/bar' compare equal, we have to make sure - * that 'foo' comes before 'foo/bar'. + * NOTE: This function will never be called with two equal strings, + * because it is used to sort the keys of a strmap, and strmaps have + * unique keys by construction. That simplifies our c1==c2 handling + * below. */ - if (cmp) - return cmp; - return onelen - twolen; + + while (*one && (*one == *two)) { + one++; + two++; + } + + c1 = *one ? *one : '/'; + c2 = *two ? *two : '/'; + + if (c1 == c2) { + /* Getting here means one is a leading directory of the other */ + return (*one) ? 1 : -1; + } else + return c1 - c2; } static int read_oid_strbuf(struct merge_options *opt, @@ -3481,7 +3508,7 @@ static void process_entries(struct merge_options *opt, trace2_region_leave("merge", "plist copy", opt->repo); trace2_region_enter("merge", "plist special sort", opt->repo); - plist.cmp = string_list_df_name_compare; + plist.cmp = sort_dirs_next_to_their_children; string_list_sort(&plist); trace2_region_leave("merge", "plist special sort", opt->repo); -- gitgitgadget