From patchwork Tue Dec 8 00:05:36 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Taylor Blau X-Patchwork-Id: 11957175 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=-13.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,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 7D28DC4167B for ; Tue, 8 Dec 2020 00:06:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 463BC23A1D for ; Tue, 8 Dec 2020 00:06:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728607AbgLHAG0 (ORCPT ); Mon, 7 Dec 2020 19:06:26 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45568 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728300AbgLHAGZ (ORCPT ); Mon, 7 Dec 2020 19:06:25 -0500 Received: from mail-ot1-x331.google.com (mail-ot1-x331.google.com [IPv6:2607:f8b0:4864:20::331]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D8E8AC061257 for ; Mon, 7 Dec 2020 16:05:39 -0800 (PST) Received: by mail-ot1-x331.google.com with SMTP id h19so14340925otr.1 for ; Mon, 07 Dec 2020 16:05:39 -0800 (PST) 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=5oK9d8MRvwLAr4PgAX2C7YmL72QhE9Q310xr6XLqZic=; b=apmt2GF7L2sLHpAH0dNeJrVXrW7pWxS8xd9OeVNtvDV69j30dkAGP9TI4qG1fCaXEQ thBPuFfTJtoSXX1XQ7H11EWcPjj8JYgavSKUd9yYmv6dOhF1Hx/eMOVDPeWcrw+AmDqN 81s+/d47HY/pu4aGt+qlPzVKzpbAlHZCrcRfzPA4BYh+hLjO8u2jqemc9OYLA3OaSf+1 tfNrcEQKcLZvZMqj639iTkNBYXYbXommFZWs8YgT6qvkOZj6LpJcjUeo3o9iQnAjpZu0 K01Ted05PD5VuuVmD4z3w57OMPxwx3viFUlvD//25uC1qpWlsCzERk5MMDkQtJu3DSwr hguw== 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=5oK9d8MRvwLAr4PgAX2C7YmL72QhE9Q310xr6XLqZic=; b=nmZU7rH7prksg2hqQO2NaQRKXGnNeRXD03xrDaeF9DSgFc2qpeHdQxvJ6TAZlQpU32 P7EM5u7YT+3YaAODLzSGWjg8u+ACfWS8aiVQPJmm66av/fWdlMaYsAFw9U/DCLw2WIka IhpDF2yvkgrpQvdc+L0CCRVDosbFAisfLTt/hfQ/bRxoLy/Vz/C4KlKjGQwLyePmZyLD G0vQIsSGCHjTEZQzIJRypLHJYG7K0B3qFM4OUjVWcUnBoWiWIDMfhwVw/uOQs3atiLSV UWA43nOHVtJ1xQx8m6RNlip4Zkbe5O+OTEMSnIjbjAo77wLhuXWHeW2vh2e8fXw0OwGo 0fyA== X-Gm-Message-State: AOAM533r76jWcwRln99nGqWQjxejZyFO3c8Y9/lK6yAcX9O3sbZdpDQp NgkR0ggPl/8Q3FxlcJ9Z9dazqYlKeaLipigw X-Google-Smtp-Source: ABdhPJyJFZrGH6Cf2jTQJu7Qnw/atyCH20E+BbsC0NAh4nv6ec6hXATZrFrtQpE2j4dq2sNLGQDV+A== X-Received: by 2002:a9d:7a97:: with SMTP id l23mr14763954otn.232.1607385938896; Mon, 07 Dec 2020 16:05:38 -0800 (PST) Received: from localhost ([8.44.146.30]) by smtp.gmail.com with ESMTPSA id n31sm1085775otn.33.2020.12.07.16.05.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 07 Dec 2020 16:05:38 -0800 (PST) Date: Mon, 7 Dec 2020 19:05:36 -0500 From: Taylor Blau To: git@vger.kernel.org Cc: peff@peff.net, jonathantanmy@google.com, dstolee@microsoft.com, gitster@pobox.com Subject: [PATCH v3 19/24] pack-bitmap-write: ignore BITMAP_FLAG_REUSE Message-ID: References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org From: Jeff King The on-disk bitmap format has a flag to mark a bitmap to be "reused". This is a rather curious feature, and works like this: - a run of pack-objects would decide to mark the last 80% of the bitmaps it generates with the reuse flag - the next time we generate bitmaps, we'd see those reuse flags from the last run, and mark those commits as special: - we'd be more likely to select those commits to get bitmaps in the new output - when generating the bitmap for a selected commit, we'd reuse the old bitmap as-is (rearranging the bits to match the new pack, of course) However, neither of these behaviors particularly makes sense. Just because a commit happened to be bitmapped last time does not make it a good candidate for having a bitmap this time. In particular, we may choose bitmaps based on how recent they are in history, or whether a ref tip points to them, and those things will change. We're better off re-considering fresh which commits are good candidates. Reusing the existing bitmap _is_ a reasonable thing to do to save computation. But only reusing exact bitmaps is a weak form of this. If we have an old bitmap for A and now want a new bitmap for its child, we should be able to compute that only by looking at trees and that are new to the child. But this code would consider only exact reuse (which is perhaps why it was eager to select those commits in the first place). Furthermore, the recent switch to the reverse-edge algorithm for generating bitmaps dropped this optimization entirely (and yet still performs better). So let's do a few cleanups: - drop the whole "reusing bitmaps" phase of generating bitmaps. It's not helping anything, and is mostly unused code (or worse, code that is using CPU but not doing anything useful) - drop the use of the on-disk reuse flag to select commits to bitmap - stop setting the on-disk reuse flag in bitmaps we generate (since nothing respects it anymore) We will keep a few innards of the reuse code, which will help us implement a more capable version of the "reuse" optimization: - simplify rebuild_existing_bitmaps() into a function that only builds the mapping of bits between the old and new orders, but doesn't actually convert any bitmaps - make rebuild_bitmap() public; we'll call it lazily to convert bitmaps as we traverse (using the mapping created above) Signed-off-by: Jeff King Signed-off-by: Taylor Blau --- builtin/pack-objects.c | 1 - pack-bitmap-write.c | 50 +++++------------------------------------- pack-bitmap.c | 46 +++++--------------------------------- pack-bitmap.h | 6 ++++- 4 files changed, 16 insertions(+), 87 deletions(-) diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c index 5617c01b5a..2a00358f34 100644 --- a/builtin/pack-objects.c +++ b/builtin/pack-objects.c @@ -1104,7 +1104,6 @@ static void write_pack_file(void) stop_progress(&progress_state); bitmap_writer_show_progress(progress); - bitmap_writer_reuse_bitmaps(&to_pack); bitmap_writer_select_commits(indexed_commits, indexed_commits_nr, -1); bitmap_writer_build(&to_pack); bitmap_writer_finish(written_list, nr_written, diff --git a/pack-bitmap-write.c b/pack-bitmap-write.c index 0af93193d8..333058854d 100644 --- a/pack-bitmap-write.c +++ b/pack-bitmap-write.c @@ -30,7 +30,6 @@ struct bitmap_writer { struct ewah_bitmap *tags; kh_oid_map_t *bitmaps; - kh_oid_map_t *reused; struct packing_data *to_pack; struct bitmapped_commit *selected; @@ -112,7 +111,7 @@ void bitmap_writer_build_type_index(struct packing_data *to_pack, * Compute the actual bitmaps */ -static inline void push_bitmapped_commit(struct commit *commit, struct ewah_bitmap *reused) +static inline void push_bitmapped_commit(struct commit *commit) { if (writer.selected_nr >= writer.selected_alloc) { writer.selected_alloc = (writer.selected_alloc + 32) * 2; @@ -120,7 +119,7 @@ static inline void push_bitmapped_commit(struct commit *commit, struct ewah_bitm } writer.selected[writer.selected_nr].commit = commit; - writer.selected[writer.selected_nr].bitmap = reused; + writer.selected[writer.selected_nr].bitmap = NULL; writer.selected[writer.selected_nr].flags = 0; writer.selected_nr++; @@ -372,13 +371,6 @@ static void store_selected(struct bb_commit *ent, struct commit *commit) khiter_t hash_pos; int hash_ret; - /* - * the "reuse bitmaps" phase may have stored something here, but - * our new algorithm doesn't use it. Drop it. - */ - if (stored->bitmap) - ewah_free(stored->bitmap); - stored->bitmap = bitmap_to_ewah(ent->bitmap); hash_pos = kh_put_oid_map(writer.bitmaps, commit->object.oid, &hash_ret); @@ -480,35 +472,6 @@ static int date_compare(const void *_a, const void *_b) return (long)b->date - (long)a->date; } -void bitmap_writer_reuse_bitmaps(struct packing_data *to_pack) -{ - struct bitmap_index *bitmap_git; - if (!(bitmap_git = prepare_bitmap_git(to_pack->repo))) - return; - - writer.reused = kh_init_oid_map(); - rebuild_existing_bitmaps(bitmap_git, to_pack, writer.reused, - writer.show_progress); - /* - * NEEDSWORK: rebuild_existing_bitmaps() makes writer.reused reference - * some bitmaps in bitmap_git, so we can't free the latter. - */ -} - -static struct ewah_bitmap *find_reused_bitmap(const struct object_id *oid) -{ - khiter_t hash_pos; - - if (!writer.reused) - return NULL; - - hash_pos = kh_get_oid_map(writer.reused, *oid); - if (hash_pos >= kh_end(writer.reused)) - return NULL; - - return kh_value(writer.reused, hash_pos); -} - void bitmap_writer_select_commits(struct commit **indexed_commits, unsigned int indexed_commits_nr, int max_bitmaps) @@ -522,12 +485,11 @@ void bitmap_writer_select_commits(struct commit **indexed_commits, if (indexed_commits_nr < 100) { for (i = 0; i < indexed_commits_nr; ++i) - push_bitmapped_commit(indexed_commits[i], NULL); + push_bitmapped_commit(indexed_commits[i]); return; } for (;;) { - struct ewah_bitmap *reused_bitmap = NULL; struct commit *chosen = NULL; next = next_commit_index(i); @@ -542,15 +504,13 @@ void bitmap_writer_select_commits(struct commit **indexed_commits, if (next == 0) { chosen = indexed_commits[i]; - reused_bitmap = find_reused_bitmap(&chosen->object.oid); } else { chosen = indexed_commits[i + next]; for (j = 0; j <= next; ++j) { struct commit *cm = indexed_commits[i + j]; - reused_bitmap = find_reused_bitmap(&cm->object.oid); - if (reused_bitmap || (cm->object.flags & NEEDS_BITMAP) != 0) { + if ((cm->object.flags & NEEDS_BITMAP) != 0) { chosen = cm; break; } @@ -560,7 +520,7 @@ void bitmap_writer_select_commits(struct commit **indexed_commits, } } - push_bitmapped_commit(chosen, reused_bitmap); + push_bitmapped_commit(chosen); i += next + 1; display_progress(writer.progress, i); diff --git a/pack-bitmap.c b/pack-bitmap.c index 60c781d100..d1368b69bb 100644 --- a/pack-bitmap.c +++ b/pack-bitmap.c @@ -1338,9 +1338,9 @@ void test_bitmap_walk(struct rev_info *revs) free_bitmap_index(bitmap_git); } -static int rebuild_bitmap(uint32_t *reposition, - struct ewah_bitmap *source, - struct bitmap *dest) +int rebuild_bitmap(const uint32_t *reposition, + struct ewah_bitmap *source, + struct bitmap *dest) { uint32_t pos = 0; struct ewah_iterator it; @@ -1369,19 +1369,11 @@ static int rebuild_bitmap(uint32_t *reposition, return 0; } -int rebuild_existing_bitmaps(struct bitmap_index *bitmap_git, - struct packing_data *mapping, - kh_oid_map_t *reused_bitmaps, - int show_progress) +uint32_t *create_bitmap_mapping(struct bitmap_index *bitmap_git, + struct packing_data *mapping) { uint32_t i, num_objects; uint32_t *reposition; - struct bitmap *rebuild; - struct stored_bitmap *stored; - struct progress *progress = NULL; - - khiter_t hash_pos; - int hash_ret; num_objects = bitmap_git->pack->num_objects; reposition = xcalloc(num_objects, sizeof(uint32_t)); @@ -1399,33 +1391,7 @@ int rebuild_existing_bitmaps(struct bitmap_index *bitmap_git, reposition[i] = oe_in_pack_pos(mapping, oe) + 1; } - rebuild = bitmap_new(); - i = 0; - - if (show_progress) - progress = start_progress("Reusing bitmaps", 0); - - kh_foreach_value(bitmap_git->bitmaps, stored, { - if (stored->flags & BITMAP_FLAG_REUSE) { - if (!rebuild_bitmap(reposition, - lookup_stored_bitmap(stored), - rebuild)) { - hash_pos = kh_put_oid_map(reused_bitmaps, - stored->oid, - &hash_ret); - kh_value(reused_bitmaps, hash_pos) = - bitmap_to_ewah(rebuild); - } - bitmap_reset(rebuild); - display_progress(progress, ++i); - } - }); - - stop_progress(&progress); - - free(reposition); - bitmap_free(rebuild); - return 0; + return reposition; } void free_bitmap_index(struct bitmap_index *b) diff --git a/pack-bitmap.h b/pack-bitmap.h index 1203120c43..afa4115136 100644 --- a/pack-bitmap.h +++ b/pack-bitmap.h @@ -73,7 +73,11 @@ void bitmap_writer_set_checksum(unsigned char *sha1); void bitmap_writer_build_type_index(struct packing_data *to_pack, struct pack_idx_entry **index, uint32_t index_nr); -void bitmap_writer_reuse_bitmaps(struct packing_data *to_pack); +uint32_t *create_bitmap_mapping(struct bitmap_index *bitmap_git, + struct packing_data *mapping); +int rebuild_bitmap(const uint32_t *reposition, + struct ewah_bitmap *source, + struct bitmap *dest); void bitmap_writer_select_commits(struct commit **indexed_commits, unsigned int indexed_commits_nr, int max_bitmaps); void bitmap_writer_build(struct packing_data *to_pack);