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| author | Derrick Stolee <derrickstolee@github.com> | 2025-02-03 17:11:06 +0000 |
|---|---|---|
| committer | Junio C Hamano <gitster@pobox.com> | 2025-02-03 16:12:42 -0800 |
| commit | bff455576750bd013a3c87b15cc7086cb8c1eab0 (patch) | |
| tree | 28c1c20f55e9da7b10e59b83d49e1ddcac775a08 /t/helper/test-path-walk.c | |
| parent | 6840fe9ee29ab51ffd7d924c624dc62da22c50bf (diff) | |
| download | git-bff455576750bd013a3c87b15cc7086cb8c1eab0.tar.gz | |
backfill: add --sparse option
One way to significantly reduce the cost of a Git clone and later fetches is
to use a blobless partial clone and combine that with a sparse-checkout that
reduces the paths that need to be populated in the working directory. Not
only does this reduce the cost of clones and fetches, the sparse-checkout
reduces the number of objects needed to download from a promisor remote.
However, history investigations can be expensive as computing blob diffs
will trigger promisor remote requests for one object at a time. This can be
avoided by downloading the blobs needed for the given sparse-checkout using
'git backfill' and its new '--sparse' mode, at a time that the user is
willing to pay that extra cost.
Note that this is distinctly different from the '--filter=sparse:<oid>'
option, as this assumes that the partial clone has all reachable trees and
we are using client-side logic to avoid downloading blobs outside of the
sparse-checkout cone. This avoids the server-side cost of walking trees
while also achieving a similar goal. It also downloads in batches based on
similar path names, presenting a resumable download if things are
interrupted.
This augments the path-walk API to have a possibly-NULL 'pl' member that may
point to a 'struct pattern_list'. This could be more general than the
sparse-checkout definition at HEAD, but 'git backfill --sparse' is currently
the only consumer.
Be sure to test this in both cone mode and not cone mode. Cone mode has the
benefit that the path-walk can skip certain paths once they would expand
beyond the sparse-checkout. Non-cone mode can describe the included files
using both positive and negative patterns, which changes the possible return
values of path_matches_pattern_list(). Test both kinds of matches for
increased coverage.
To test this, we can create a blobless sparse clone, expand the
sparse-checkout slightly, and then run 'git backfill --sparse' to see
how much data is downloaded. The general steps are
1. git clone --filter=blob:none --sparse <url>
2. git sparse-checkout set <dir1> ... <dirN>
3. git backfill --sparse
For the Git repository with the 'builtin' directory in the
sparse-checkout, we get these results for various batch sizes:
| Batch Size | Pack Count | Pack Size | Time |
|-----------------|------------|-----------|-------|
| (Initial clone) | 3 | 110 MB | |
| 10K | 12 | 192 MB | 17.2s |
| 15K | 9 | 192 MB | 15.5s |
| 20K | 8 | 192 MB | 15.5s |
| 25K | 7 | 192 MB | 14.7s |
This case matters less because a full clone of the Git repository from
GitHub is currently at 277 MB.
Using a copy of the Linux repository with the 'kernel/' directory in the
sparse-checkout, we get these results:
| Batch Size | Pack Count | Pack Size | Time |
|-----------------|------------|-----------|------|
| (Initial clone) | 2 | 1,876 MB | |
| 10K | 11 | 2,187 MB | 46s |
| 25K | 7 | 2,188 MB | 43s |
| 50K | 5 | 2,194 MB | 44s |
| 100K | 4 | 2,194 MB | 48s |
This case is more meaningful because a full clone of the Linux
repository is currently over 6 GB, so this is a valuable way to download
a fraction of the repository and no longer need network access for all
reachable objects within the sparse-checkout.
Choosing a batch size will depend on a lot of factors, including the
user's network speed or reliability, the repository's file structure,
and how many versions there are of the file within the sparse-checkout
scope. There will not be a one-size-fits-all solution.
Signed-off-by: Derrick Stolee <stolee@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 't/helper/test-path-walk.c')
| -rw-r--r-- | t/helper/test-path-walk.c | 22 |
1 files changed, 21 insertions, 1 deletions
diff --git a/t/helper/test-path-walk.c b/t/helper/test-path-walk.c index 7f2d409c5b..61e845e5ec 100644 --- a/t/helper/test-path-walk.c +++ b/t/helper/test-path-walk.c @@ -1,6 +1,7 @@ #define USE_THE_REPOSITORY_VARIABLE #include "test-tool.h" +#include "dir.h" #include "environment.h" #include "hex.h" #include "object-name.h" @@ -9,6 +10,7 @@ #include "revision.h" #include "setup.h" #include "parse-options.h" +#include "strbuf.h" #include "path-walk.h" #include "oid-array.h" @@ -65,7 +67,7 @@ static int emit_block(const char *path, struct oid_array *oids, int cmd__path_walk(int argc, const char **argv) { - int res; + int res, stdin_pl = 0; struct rev_info revs = REV_INFO_INIT; struct path_walk_info info = PATH_WALK_INFO_INIT; struct path_walk_test_data data = { 0 }; @@ -80,6 +82,8 @@ int cmd__path_walk(int argc, const char **argv) N_("toggle inclusion of tree objects")), OPT_BOOL(0, "prune", &info.prune_all_uninteresting, N_("toggle pruning of uninteresting paths")), + OPT_BOOL(0, "stdin-pl", &stdin_pl, + N_("read a pattern list over stdin")), OPT_END(), }; @@ -99,6 +103,17 @@ int cmd__path_walk(int argc, const char **argv) info.path_fn = emit_block; info.path_fn_data = &data; + if (stdin_pl) { + struct strbuf in = STRBUF_INIT; + CALLOC_ARRAY(info.pl, 1); + + info.pl->use_cone_patterns = 1; + + strbuf_fread(&in, 2048, stdin); + add_patterns_from_buffer(in.buf, in.len, "", 0, info.pl); + strbuf_release(&in); + } + res = walk_objects_by_path(&info); printf("commits:%" PRIuMAX "\n" @@ -107,6 +122,11 @@ int cmd__path_walk(int argc, const char **argv) "tags:%" PRIuMAX "\n", data.commit_nr, data.tree_nr, data.blob_nr, data.tag_nr); + if (info.pl) { + clear_pattern_list(info.pl); + free(info.pl); + } + release_revisions(&revs); return res; } |