From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_PASS,SPF_PASS shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by dcvr.yhbt.net (Postfix) with ESMTP id 3CF151F9FF for ; Tue, 30 Mar 2021 15:05:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232327AbhC3PFB (ORCPT ); Tue, 30 Mar 2021 11:05:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53152 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231782AbhC3PEi (ORCPT ); Tue, 30 Mar 2021 11:04:38 -0400 Received: from mail-il1-x134.google.com (mail-il1-x134.google.com [IPv6:2607:f8b0:4864:20::134]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 58090C061574 for ; Tue, 30 Mar 2021 08:04:38 -0700 (PDT) Received: by mail-il1-x134.google.com with SMTP id h7so7290529ilj.8 for ; Tue, 30 Mar 2021 08:04:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ttaylorr-com.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=3nVkSUnCuRKdX/20i8p1f+C/avnQBDdAKi+Iv4n5nPE=; b=uMg5e8aCTkmRjo/9WvJbMYgFRUmm1nXJivCweYpTdFpeszndwXkAMQMWOO+yKKmTr/ evvDxIzNYxH9PyF8Iye3HkVR7xrwyUz40M7/B5ylqkjsIwcIwhR66HH+2z6Am8lQRr+3 TPgf40nz0T8aVJ0HoAXyF/1fQw/9z0RBNf4FslcPePnqvf9AxO2/QvTdiYicrIvpoBSj qTpTzknTX/Ha/7+5X8YVuEM4E4LKX6p5KVKiboegzZAtxv5d3uHinIddz9Fr5Q4OReHo MQf9jIZRKuPOjoreUc/PmCYX8MjV4LrP6q4pTpPm9IdgSSonvrhxeJFGkC5/jgXzPHYU kp2Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=3nVkSUnCuRKdX/20i8p1f+C/avnQBDdAKi+Iv4n5nPE=; b=XFBYRtKhwodpkD2qmX8Xqu6B5mDC0WkXGAmPQdfQ8SAU1MEAN+7PW/PcftcO9aUue7 /YBNx7JLBojUp87MKgBwjImprD+NFaOFA0/qgYVssWoOAH9wKujuk4r4ZpBhFRs99qSn nD0j+HhphN/ZpkbqLcPAk9nXgUxkFKtvfztOhvG8d87yD38VPWE4PdZnguW1rbMZLPJw oKmYm90SVEQD2XVupP9QDORwR4JtJZk8phnB8kbylKCHlgkMtYC4nLeEzqJUtj+onNpd zWMe274NLv3FVinGZoQ7pctY0tuhH/u/iLd3A8j9TaKWwH6BfOwyme73XHdadbmeM5Z+ VWfw== X-Gm-Message-State: AOAM531e50uDBJt7XLg/rqxhkyVt6PXcQV8DV29bA6W1atCkwBurCLv7 5jwPXz46k32imypQH+s5q5Qh0zPJMRYsYA== X-Google-Smtp-Source: ABdhPJwQV6eR+5JAw1MZpwCox/qup65jKSUY4oyVlMRNLB0/59A52cdu/MaZb7rEt661MmxyYJTp4w== X-Received: by 2002:a05:6e02:1a8d:: with SMTP id k13mr14029580ilv.3.1617116677566; Tue, 30 Mar 2021 08:04:37 -0700 (PDT) Received: from localhost ([2605:9480:22e:ff10:7b00:4f79:8763:6261]) by smtp.gmail.com with ESMTPSA id x4sm8595121ilm.39.2021.03.30.08.04.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 30 Mar 2021 08:04:37 -0700 (PDT) Date: Tue, 30 Mar 2021 11:04:36 -0400 From: Taylor Blau To: git@vger.kernel.org Cc: gitster@pobox.com, peff@peff.net, dstolee@microsoft.com, jonathantanmy@google.com Subject: [PATCH v4 16/16] midx.c: improve cache locality in midx_pack_order_cmp() Message-ID: <7b793e7d0918bc5869f9c2aef818fdd7353ea77b.1617116623.git.me@ttaylorr.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org From: Jeff King There is a lot of pointer dereferencing in the pre-image version of 'midx_pack_order_cmp()', which this patch gets rid of. Instead of comparing the pack preferred-ness and then the pack id, both of these checks are done at the same time by using the high-order bit of the pack id to represent whether it's preferred. Then the pack id and offset are compared as usual. This produces the same result so long as there are less than 2^31 packs, which seems like a likely assumption to make in practice. Signed-off-by: Jeff King Signed-off-by: Taylor Blau --- midx.c | 55 +++++++++++++++++++++++++++++-------------------------- 1 file changed, 29 insertions(+), 26 deletions(-) diff --git a/midx.c b/midx.c index b96eaa12fb..9e86583172 100644 --- a/midx.c +++ b/midx.c @@ -818,46 +818,49 @@ static int write_midx_large_offsets(struct hashfile *f, return 0; } -static int midx_pack_order_cmp(const void *va, const void *vb, void *_ctx) +struct midx_pack_order_data { + uint32_t nr; + uint32_t pack; + off_t offset; +}; + +static int midx_pack_order_cmp(const void *va, const void *vb) { - struct write_midx_context *ctx = _ctx; - - struct pack_midx_entry *a = &ctx->entries[*(const uint32_t *)va]; - struct pack_midx_entry *b = &ctx->entries[*(const uint32_t *)vb]; - - uint32_t perm_a = ctx->pack_perm[a->pack_int_id]; - uint32_t perm_b = ctx->pack_perm[b->pack_int_id]; - - /* Sort objects in the preferred pack ahead of any others. */ - if (a->preferred > b->preferred) + const struct midx_pack_order_data *a = va, *b = vb; + if (a->pack < b->pack) return -1; - if (a->preferred < b->preferred) + else if (a->pack > b->pack) return 1; - - /* Then, order objects by which packs they appear in. */ - if (perm_a < perm_b) + else if (a->offset < b->offset) return -1; - if (perm_a > perm_b) + else if (a->offset > b->offset) return 1; - - /* Then, disambiguate by their offset within each pack. */ - if (a->offset < b->offset) - return -1; - if (a->offset > b->offset) - return 1; - - return 0; + else + return 0; } static uint32_t *midx_pack_order(struct write_midx_context *ctx) { + struct midx_pack_order_data *data; uint32_t *pack_order; uint32_t i; + ALLOC_ARRAY(data, ctx->entries_nr); + for (i = 0; i < ctx->entries_nr; i++) { + struct pack_midx_entry *e = &ctx->entries[i]; + data[i].nr = i; + data[i].pack = ctx->pack_perm[e->pack_int_id]; + if (!e->preferred) + data[i].pack |= (1U << 31); + data[i].offset = e->offset; + } + + QSORT(data, ctx->entries_nr, midx_pack_order_cmp); + ALLOC_ARRAY(pack_order, ctx->entries_nr); for (i = 0; i < ctx->entries_nr; i++) - pack_order[i] = i; - QSORT_S(pack_order, ctx->entries_nr, midx_pack_order_cmp, ctx); + pack_order[i] = data[i].nr; + free(data); return pack_order; } -- 2.30.0.667.g81c0cbc6fd