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diff: restrict when prefetching occurs 

Commit 7fbbcb21b1 ("diff: batch fetching of missing blobs", 2019-04-08)
optimized "diff" by prefetching blobs in a partial clone, but there are
some cases wherein blobs do not need to be prefetched. In these cases,
any command that uses the diff machinery will unnecessarily fetch blobs.

diffcore_std() may read blobs when it calls the following functions:
 (1) diffcore_skip_stat_unmatch() (controlled by the config variable
     diff.autorefreshindex)
 (2) diffcore_break() and diffcore_merge_broken() (for break-rewrite
     detection)
 (3) diffcore_rename() (for rename detection)
 (4) diffcore_pickaxe() (for detecting addition/deletion of specified
     string)

Instead of always prefetching blobs, teach diffcore_skip_stat_unmatch(),
diffcore_break(), and diffcore_rename() to prefetch blobs upon the first
read of a missing object. This covers (1), (2), and (3): to cover the
rest, teach diffcore_std() to prefetch if the output type is one that
includes blob data (and hence blob data will be required later anyway),
or if it knows that (4) will be run.

Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Jonathan Tan 2020-04-07 15:11:43 -07:00 committed by Junio C Hamano
parent c14b6f83ec
commit 95acf11a3d
5 changed files with 181 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

73
diff.c
View File

@ -4034,10 +4034,18 @@ int diff_populate_filespec(struct repository *r,
*/
info.contentp = &s->data;
if (options && options->missing_object_cb) {
if (!oid_object_info_extended(r, &s->oid, &info,
OBJECT_INFO_LOOKUP_REPLACE |
OBJECT_INFO_SKIP_FETCH_OBJECT))
goto object_read;
options->missing_object_cb(options->missing_object_data);
}
if (oid_object_info_extended(r, &s->oid, &info,
OBJECT_INFO_LOOKUP_REPLACE))
die("unable to read %s", oid_to_hex(&s->oid));
object_read:
if (size_only || check_binary) {
if (size_only)
return 0;
@ -6444,6 +6452,8 @@ static int diff_filespec_check_stat_unmatch(struct repository *r,
{
struct diff_populate_filespec_options dpf_options = {
.check_size_only = 1,
.missing_object_cb = diff_queued_diff_prefetch,
.missing_object_data = r,
};
if (p->done_skip_stat_unmatch)
@ -6520,9 +6530,9 @@ void diffcore_fix_diff_index(void)
QSORT(q->queue, q->nr, diffnamecmp);
}
static void add_if_missing(struct repository *r,
struct oid_array *to_fetch,
const struct diff_filespec *filespec)
void diff_add_if_missing(struct repository *r,
struct oid_array *to_fetch,
const struct diff_filespec *filespec)
{
if (filespec && filespec->oid_valid &&
!S_ISGITLINK(filespec->mode) &&
@ -6531,28 +6541,47 @@ static void add_if_missing(struct repository *r,
oid_array_append(to_fetch, &filespec->oid);
}
void diff_queued_diff_prefetch(void *repository)
{
struct repository *repo = repository;
int i;
struct diff_queue_struct *q = &diff_queued_diff;
struct oid_array to_fetch = OID_ARRAY_INIT;
for (i = 0; i < q->nr; i++) {
struct diff_filepair *p = q->queue[i];
diff_add_if_missing(repo, &to_fetch, p->one);
diff_add_if_missing(repo, &to_fetch, p->two);
}
/*
* NEEDSWORK: Consider deduplicating the OIDs sent.
*/
promisor_remote_get_direct(repo, to_fetch.oid, to_fetch.nr);
oid_array_clear(&to_fetch);
}
void diffcore_std(struct diff_options *options)
{
if (options->repo == the_repository && has_promisor_remote()) {
/*
* Prefetch the diff pairs that are about to be flushed.
*/
int i;
struct diff_queue_struct *q = &diff_queued_diff;
struct oid_array to_fetch = OID_ARRAY_INIT;
int output_formats_to_prefetch = DIFF_FORMAT_DIFFSTAT |
DIFF_FORMAT_NUMSTAT |
DIFF_FORMAT_PATCH |
DIFF_FORMAT_SHORTSTAT |
DIFF_FORMAT_DIRSTAT;
for (i = 0; i < q->nr; i++) {
struct diff_filepair *p = q->queue[i];
add_if_missing(options->repo, &to_fetch, p->one);
add_if_missing(options->repo, &to_fetch, p->two);
}
/*
* NEEDSWORK: Consider deduplicating the OIDs sent.
*/
promisor_remote_get_direct(options->repo,
to_fetch.oid, to_fetch.nr);
oid_array_clear(&to_fetch);
}
/*
* Check if the user requested a blob-data-requiring diff output and/or
* break-rewrite detection (which requires blob data). If yes, prefetch
* the diff pairs.
*
* If no prefetching occurs, diffcore_rename() will prefetch if it
* decides that it needs inexact rename detection.
*/
if (options->repo == the_repository && has_promisor_remote() &&
(options->output_format & output_formats_to_prefetch ||
options->pickaxe_opts & DIFF_PICKAXE_KINDS_MASK))
diff_queued_diff_prefetch(options->repo);
/* NOTE please keep the following in sync with diff_tree_combined() */
if (options->skip_stat_unmatch)

12
diffcore-break.c
View File

@ -4,6 +4,7 @@
#include "cache.h"
#include "diff.h"
#include "diffcore.h"
#include "promisor-remote.h"
static int should_break(struct repository *r,
struct diff_filespec *src,
@ -49,6 +50,8 @@ static int should_break(struct repository *r,
unsigned long delta_size, max_size;
unsigned long src_copied, literal_added, src_removed;
struct diff_populate_filespec_options options = { 0 };
*merge_score_p = 0; /* assume no deletion --- "do not break"
* is the default.
*/
@ -62,8 +65,13 @@ static int should_break(struct repository *r,
oideq(&src->oid, &dst->oid))
return 0; /* they are the same */
if (diff_populate_filespec(r, src, NULL) ||
diff_populate_filespec(r, dst, NULL))
if (r == the_repository && has_promisor_remote()) {
options.missing_object_cb = diff_queued_diff_prefetch;
options.missing_object_data = r;
}
if (diff_populate_filespec(r, src, &options) ||
diff_populate_filespec(r, dst, &options))
return 0; /* error but caught downstream */
max_size = ((src->size > dst->size) ? src->size : dst->size);

55
diffcore-rename.c
View File

@ -1,4 +1,5 @@
/*
*
* Copyright (C) 2005 Junio C Hamano
*/
#include "cache.h"
@ -7,6 +8,7 @@
#include "object-store.h"
#include "hashmap.h"
#include "progress.h"
#include "promisor-remote.h"
/* Table of rename/copy destinations */
@ -128,10 +130,46 @@ struct diff_score {
short name_score;
};
struct prefetch_options {
struct repository *repo;
int skip_unmodified;
};
static void prefetch(void *prefetch_options)
{
struct prefetch_options *options = prefetch_options;
int i;
struct oid_array to_fetch = OID_ARRAY_INIT;
for (i = 0; i < rename_dst_nr; i++) {
if (rename_dst[i].pair)
/*
* The loop in diffcore_rename() will not need these
* blobs, so skip prefetching.
*/
continue; /* already found exact match */
diff_add_if_missing(options->repo, &to_fetch,
rename_dst[i].two);
}
for (i = 0; i < rename_src_nr; i++) {
if (options->skip_unmodified &&
diff_unmodified_pair(rename_src[i].p))
/*
* The loop in diffcore_rename() will not need these
* blobs, so skip prefetching.
*/
continue;
diff_add_if_missing(options->repo, &to_fetch,
rename_src[i].p->one);
}
promisor_remote_get_direct(options->repo, to_fetch.oid, to_fetch.nr);
oid_array_clear(&to_fetch);
}
static int estimate_similarity(struct repository *r,
struct diff_filespec *src,
struct diff_filespec *dst,
int minimum_score)
int minimum_score,
int skip_unmodified)
{
/* src points at a file that existed in the original tree (or
* optionally a file in the destination tree) and dst points
@ -151,6 +189,12 @@ static int estimate_similarity(struct repository *r,
struct diff_populate_filespec_options dpf_options = {
.check_size_only = 1
};
struct prefetch_options prefetch_options = {r, skip_unmodified};
if (r == the_repository && has_promisor_remote()) {
dpf_options.missing_object_cb = prefetch;
dpf_options.missing_object_data = &prefetch_options;
}
/* We deal only with regular files. Symlink renames are handled
* only when they are exact matches --- in other words, no edits
@ -190,9 +234,11 @@ static int estimate_similarity(struct repository *r,
if (max_size * (MAX_SCORE-minimum_score) < delta_size * MAX_SCORE)
return 0;
if (!src->cnt_data && diff_populate_filespec(r, src, NULL))
dpf_options.check_size_only = 0;
if (!src->cnt_data && diff_populate_filespec(r, src, &dpf_options))
return 0;
if (!dst->cnt_data && diff_populate_filespec(r, dst, NULL))
if (!dst->cnt_data && diff_populate_filespec(r, dst, &dpf_options))
return 0;
if (diffcore_count_changes(r, src, dst,
@ -569,7 +615,8 @@ void diffcore_rename(struct diff_options *options)
this_src.score = estimate_similarity(options->repo,
one, two,
minimum_score);
minimum_score,
skip_unmodified);
this_src.name_score = basename_same(one, two);
this_src.dst = i;
this_src.src = j;

21
diffcore.h
View File

@ -65,9 +65,22 @@ void free_filespec(struct diff_filespec *);
void fill_filespec(struct diff_filespec *, const struct object_id *,
int, unsigned short);
/*
* Prefetch the entries in diff_queued_diff. The parameter is a pointer to a
* struct repository.
*/
void diff_queued_diff_prefetch(void *repository);
struct diff_populate_filespec_options {
unsigned check_size_only : 1;
unsigned check_binary : 1;
/*
* If an object is missing, diff_populate_filespec() will invoke this
* callback before attempting to read that object again.
*/
void (*missing_object_cb)(void *);
void *missing_object_data;
};
int diff_populate_filespec(struct repository *, struct diff_filespec *,
const struct diff_populate_filespec_options *);
@ -185,4 +198,12 @@ int diffcore_count_changes(struct repository *r,
unsigned long *src_copied,
unsigned long *literal_added);
/*
* If filespec contains an OID and if that object is missing from the given
* repository, add that OID to to_fetch.
*/
void diff_add_if_missing(struct repository *r,
struct oid_array *to_fetch,
const struct diff_filespec *filespec);
#endif

48
t/t4067-diff-partial-clone.sh
View File

@ -131,4 +131,52 @@ test_expect_success 'diff with rename detection batches blobs' '
test_line_count = 1 done_lines
'
test_expect_success 'diff does not fetch anything if inexact rename detection is not needed' '
test_when_finished "rm -rf server client trace" &&
test_create_repo server &&
echo a >server/a &&
printf "b\nb\nb\nb\nb\n" >server/b &&
git -C server add a b &&
git -C server commit -m x &&
mv server/b server/c &&
git -C server add c &&
git -C server commit -a -m x &&
test_config -C server uploadpack.allowfilter 1 &&
test_config -C server uploadpack.allowanysha1inwant 1 &&
git clone --bare --filter=blob:limit=0 "file://$(pwd)/server" client &&
# Ensure no fetches.
GIT_TRACE_PACKET="$(pwd)/trace" git -C client diff --raw -M HEAD^ HEAD &&
! test_path_exists trace
'
test_expect_success 'diff --break-rewrites fetches only if necessary, and batches blobs if it does' '
test_when_finished "rm -rf server client trace" &&
test_create_repo server &&
echo a >server/a &&
printf "b\nb\nb\nb\nb\n" >server/b &&
git -C server add a b &&
git -C server commit -m x &&
printf "c\nc\nc\nc\nc\n" >server/b &&
git -C server commit -a -m x &&
test_config -C server uploadpack.allowfilter 1 &&
test_config -C server uploadpack.allowanysha1inwant 1 &&
git clone --bare --filter=blob:limit=0 "file://$(pwd)/server" client &&
# Ensure no fetches.
GIT_TRACE_PACKET="$(pwd)/trace" git -C client diff --raw -M HEAD^ HEAD &&
! test_path_exists trace &&
# But with --break-rewrites, ensure that there is exactly 1 negotiation
# by checking that there is only 1 "done" line sent. ("done" marks the
# end of negotiation.)
GIT_TRACE_PACKET="$(pwd)/trace" git -C client diff --break-rewrites --raw -M HEAD^ HEAD &&
grep "git> done" trace >done_lines &&
test_line_count = 1 done_lines
'
test_done