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Nguyễn Thái Ngọc Duy c9018b0305 pack-objects: refactor write_object() into helper functions
The function first decides if we want to copy data taken from existing
pack verbatim or we want to encode the data ourselves for the packfile
we are creating and then carries out the decision.  Separate the latter
phase into two helper functions, one for the case the data is reused,
the other for the case the data is produced anew.

A little twist is that it can later turn out that we cannot reuse the
data after we initially decide to do so; in such a case, the "reuse"
helper makes a call to "generate" helper.  It is easier to follow than
the current fallback code that uses "goto" inside a single large
function.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2012-05-18 14:22:15 -07:00
Nguyễn Thái Ngọc Duy 754980d023 pack-objects, streaming: turn "xx >= big_file_threshold" to ".. > .."
This is because all other places do "xx > big_file_threshold"

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2012-05-18 14:21:19 -07:00
Jeff King 7e52f5660e gc: do not explode objects which will be immediately pruned
When we pack everything into one big pack with "git repack
-Ad", any unreferenced objects in to-be-deleted packs are
exploded into loose objects, with the intent that they will
be examined and possibly cleaned up by the next run of "git
prune".

Since the exploded objects will receive the mtime of the
pack from which they come, if the source pack is old, those
loose objects will end up pruned immediately. In that case,
it is much more efficient to skip the exploding step
entirely for these objects.

This patch teaches pack-objects to receive the expiration
information and avoid writing these objects out. It also
teaches "git gc" to pass the value of gc.pruneexpire to
repack (which in turn learns to pass it along to
pack-objects) so that this optimization happens
automatically during "git gc" and "git gc --auto".

Signed-off-by: Jeff King <peff@peff.net>
Acked-by: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2012-04-11 11:09:49 -07:00
Michał Kiedrowicz 2b34e486bc pack-objects: Fix compilation with NO_PTHREDS
It looks like commit 99fb6e04 (pack-objects: convert to use
parse_options(), 2012-02-01) moved the #ifdef NO_PTHREDS around but
hasn't noticed that the 'arg' variable no longer is available.

Signed-off-by: Michał Kiedrowicz <michal.kiedrowicz@gmail.com>
Acked-by: Nguyen Thai Ngoc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2012-02-26 17:46:00 -08:00
Nguyễn Thái Ngọc Duy 99fb6e04cb pack-objects: convert to use parse_options()
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2012-02-01 13:05:00 -08:00
Nguyễn Thái Ngọc Duy 3a2ec52e99 pack-objects: remove bogus comment
The comment was introduced in b5d97e6 (pack-objects: run rev-list
equivalent internally. - 2006-09-04), stating that

git pack-objects [options] base-name <refs...>

is acceptable and refs should be passed into rev-list. But that's not
true. All arguments after base-name are ignored.

Remove the comment and reject this syntax (i.e. no more arguments after
base name)

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2012-02-01 13:04:11 -08:00
Nguyễn Thái Ngọc Duy 6a301345a5 pack-objects: do not accept "--index-version=version,"
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2012-02-01 13:03:46 -08:00
Junio C Hamano c4a01a3cbb Merge branch 'maint'
* maint:
  Update draft release notes to 1.7.8.4
  Update draft release notes to 1.7.7.6
  Update draft release notes to 1.7.6.6
  thin-pack: try harder to use preferred base objects as base
2012-01-12 23:33:39 -08:00
Junio C Hamano 5a6a939481 Merge branch 'maint-1.7.7' into maint
* maint-1.7.7:
  Update draft release notes to 1.7.7.6
  Update draft release notes to 1.7.6.6
  thin-pack: try harder to use preferred base objects as base
2012-01-12 23:31:46 -08:00
Junio C Hamano 901c907d83 Merge branch 'maint-1.7.6' into maint-1.7.7
* maint-1.7.6:
  Update draft release notes to 1.7.6.6
  thin-pack: try harder to use preferred base objects as base
2012-01-12 23:31:05 -08:00
Jeff King 15f07e061e thin-pack: try harder to use preferred base objects as base
When creating a pack using objects that reside in existing packs, we try
to avoid recomputing futile delta between an object (trg) and a candidate
for its base object (src) if they are stored in the same packfile, and trg
is not recorded as a delta already. This heuristics makes sense because it
is likely that we tried to express trg as a delta based on src but it did
not produce a good delta when we created the existing pack.

As the pack heuristics prefer producing delta to remove data, and Linus's
law dictates that the size of a file grows over time, we tend to record
the newest version of the file as inflated, and older ones as delta
against it.

When creating a thin-pack to transfer recent history, it is likely that we
will try to send an object that is recorded in full, as it is newer.  But
the heuristics to avoid recomputing futile delta effectively forbids us
from attempting to express such an object as a delta based on another
object. Sending an object in full is often more expensive than sending a
suboptimal delta based on other objects, and it is even more so if we
could use an object we know the receiving end already has (i.e. preferred
base object) as the delta base.

Tweak the recomputation avoidance logic, so that we do not punt on
computing delta against a preferred base object.

The effect of this change can be seen on two simulated upload-pack
workloads. The first is based on 44 reflog entries from my git.git
origin/master reflog, and represents the packs that kernel.org sent me git
updates for the past month or two. The second workload represents much
larger fetches, going from git's v1.0.0 tag to v1.1.0, then v1.1.0 to
v1.2.0, and so on.

The table below shows the average generated pack size and the average CPU
time consumed for each dataset, both before and after the patch:

                  dataset
            | reflog | tags
---------------------------------
     before | 53358  | 2750977
size  after | 32398  | 2668479
     change |   -39% |      -3%
---------------------------------
     before |  0.18  | 1.12
CPU   after |  0.18  | 1.15
     change |    +0% |      +3%

This patch makes a much bigger difference for packs with a shorter slice
of history (since its effect is seen at the boundaries of the pack) though
it has some benefit even for larger packs.

Signed-off-by: Jeff King <peff@peff.net>
Acked-by: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2012-01-12 23:06:20 -08:00
Junio C Hamano 48b303675a Merge branch 'jc/stream-to-pack'
* jc/stream-to-pack:
  bulk-checkin: replace fast-import based implementation
  csum-file: introduce sha1file_checkpoint
  finish_tmp_packfile(): a helper function
  create_tmp_packfile(): a helper function
  write_pack_header(): a helper function

Conflicts:
	pack.h
2011-12-16 22:33:40 -08:00
Junio C Hamano 2e8722fc9e Merge branch 'jc/maint-pack-object-cycle' into maint
* jc/maint-pack-object-cycle:
  pack-object: tolerate broken packs that have duplicated objects

Conflicts:
	builtin/pack-objects.c
2011-12-13 22:04:50 -08:00
Junio C Hamano df6246ed78 Merge branch 'nd/misc-cleanups' into maint
* nd/misc-cleanups:
  unpack_object_header_buffer(): clear the size field upon error
  tree_entry_interesting: make use of local pointer "item"
  tree_entry_interesting(): give meaningful names to return values
  read_directory_recursive: reduce one indentation level
  get_tree_entry(): do not call find_tree_entry() on an empty tree
  tree-walk.c: do not leak internal structure in tree_entry_len()
2011-12-13 22:02:51 -08:00
Junio C Hamano cddec4f8ae Merge branch 'jc/maint-pack-object-cycle'
* jc/maint-pack-object-cycle:
  pack-object: tolerate broken packs that have duplicated objects

Conflicts:
	builtin/pack-objects.c
2011-12-05 15:19:34 -08:00
Junio C Hamano 62cdb6b23a Merge branch 'nd/misc-cleanups'
* nd/misc-cleanups:
  unpack_object_header_buffer(): clear the size field upon error
  tree_entry_interesting: make use of local pointer "item"
  tree_entry_interesting(): give meaningful names to return values
  read_directory_recursive: reduce one indentation level
  get_tree_entry(): do not call find_tree_entry() on an empty tree
  tree-walk.c: do not leak internal structure in tree_entry_len()
2011-12-05 15:10:20 -08:00
Junio C Hamano 568508e765 bulk-checkin: replace fast-import based implementation
This extends the earlier approach to stream a large file directly from the
filesystem to its own packfile, and allows "git add" to send large files
directly into a single pack. Older code used to spawn fast-import, but the
new bulk-checkin API replaces it.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2011-12-01 11:46:09 -08:00
Junio C Hamano f63c79dbc8 pack-object: tolerate broken packs that have duplicated objects
When --reuse-delta is in effect (which is the default), and an existing
pack in the repository has the same object registered twice (e.g. one copy
in a non-delta format and the other copy in a delta against some other
object), an attempt to repack the repository can result in a cyclic delta
dependency, causing write_one() function to infinitely recurse into
itself.

Detect such a case and break the loopy dependency by writing out an object
that is involved in such a loop in the non-delta format.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2011-11-16 22:06:08 -08:00
Junio C Hamano 84a9ea90e1 Merge branch 'dm/pack-objects-update'
* dm/pack-objects-update:
  pack-objects: don't traverse objects unnecessarily
  pack-objects: rewrite add_descendants_to_write_order() iteratively
  pack-objects: use unsigned int for counter and offset values
  pack-objects: mark add_to_write_order() as inline
2011-11-01 15:20:07 -07:00
Junio C Hamano 0e990530ae finish_tmp_packfile(): a helper function
Factor out a small logic out of the private write_pack_file() function
in builtin/pack-objects.c.

This changes the order of finishing multi-pack generation slightly. The
code used to

 - adjust shared perm of temporary packfile
 - rename temporary packfile to the final name
 - update mtime of the packfile under the final name
 - adjust shared perm of temporary idxfile
 - rename temporary idxfile to the final name

but because the helper does not want to do the mtime thing, the updated
code does that step first and then all the rest.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2011-10-28 12:34:09 -07:00
Junio C Hamano cdf9db3c83 create_tmp_packfile(): a helper function
Factor out a small logic out of the private write_pack_file() function
in builtin/pack-objects.c

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2011-10-28 11:52:14 -07:00
Junio C Hamano c0ad465725 write_pack_header(): a helper function
Factor out a small logic out of the private write_pack_file() function
in builtin/pack-objects.c

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2011-10-28 11:40:48 -07:00
Nguyễn Thái Ngọc Duy 0de1633783 tree-walk.c: do not leak internal structure in tree_entry_len()
tree_entry_len() does not simply take two random arguments and return
a tree length. The two pointers must point to a tree item structure,
or struct name_entry. Passing random pointers will return incorrect
value.

Force callers to pass struct name_entry instead of two pointers (with
hope that they don't manually construct struct name_entry themselves)

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2011-10-27 11:08:26 -07:00
Junio C Hamano 2070950633 Merge branch 'jk/maint-pack-objects-compete-with-delete'
* jk/maint-pack-objects-compete-with-delete:
  downgrade "packfile cannot be accessed" errors to warnings
  pack-objects: protect against disappearing packs
2011-10-21 16:04:33 -07:00
Dan McGee 38d4debb6d pack-objects: don't traverse objects unnecessarily
This brings back some of the performance lost in optimizing recency
order inside pack objects. We were doing extreme amounts of object
re-traversal: for the 2.14 million objects in the Linux kernel
repository, we were calling add_to_write_order() over 1.03 billion times
(a 0.2% hit rate, making 99.8% of of these calls extraneous).

Two optimizations take place here- we can start our objects array
iteration from a known point where we left off before we started trying
to find our tags, and we don't need to do the deep dives required by
add_family_to_write_order() if the object has already been marked as
filled.

These two optimizations bring some pretty spectacular results via `perf
stat`:

task-clock:   83373 ms        --> 43800 ms         (50% faster)
cycles:       221,633,461,676 --> 116,307,209,986  (47% fewer)
instructions: 149,299,179,939 --> 122,998,800,184  (18% fewer)

Helped-by: Ramsay Jones (format string fix in "die" message)
Signed-off-by: Dan McGee <dpmcgee@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2011-10-20 17:17:49 -07:00
Dan McGee f380872f0a pack-objects: rewrite add_descendants_to_write_order() iteratively
This removes the need to call this function recursively, shinking the
code size slightly and netting a small performance increase.

Signed-off-by: Dan McGee <dpmcgee@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2011-10-18 00:16:32 -07:00
Dan McGee 92bef1a14a pack-objects: use unsigned int for counter and offset values
This is done in some of the new pack layout code introduced in commit
1b4bb16b9e. This more closely matches the nr_objects global that is
unsigned that these variables are based off of and bounded by.

Signed-off-by: Dan McGee <dpmcgee@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2011-10-18 00:16:32 -07:00
Dan McGee be12681896 pack-objects: mark add_to_write_order() as inline
This function is a whole 26 bytes when compiled on x86_64, but is
currently invoked over 1.037 billion times when running pack-objects on
the Linux kernel git repository. This is hitting the point where
micro-optimizations do make a difference, and inlining it only increases
the object file size by 38 bytes.

As reported by perf, this dropped task-clock from 84183 to 83373 ms, and
total cycles from 223.5 billion to 221.6 billion. Not astronomical, but
worth getting for adding one word.

Signed-off-by: Dan McGee <dpmcgee@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2011-10-18 00:16:31 -07:00
Jeff King 58a6a9cc43 downgrade "packfile cannot be accessed" errors to warnings
These can happen if another process simultaneously prunes a
pack. But that is not usually an error condition, because a
properly-running prune should have repacked the object into
a new pack. So we will notice that the pack has disappeared
unexpectedly, print a message, try other packs (possibly
after re-scanning the list of packs), and find it in the new
pack.

Acked-by: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2011-10-14 11:43:09 -07:00
Jeff King 4c08018204 pack-objects: protect against disappearing packs
It's possible that while pack-objects is running, a
simultaneously running prune process might delete a pack
that we are interested in. Because we load the pack indices
early on, we know that the pack contains our item, but by
the time we try to open and map it, it is gone.

Since c715f78, we already protect against this in the normal
object access code path, but pack-objects accesses the packs
at a lower level.  In the normal access path, we call
find_pack_entry, which will call find_pack_entry_one on each
pack index, which does the actual lookup. If it gets a hit,
we will actually open and verify the validity of the
matching packfile (using c715f78's is_pack_valid). If we
can't open it, we'll issue a warning and pretend that we
didn't find it, causing us to go on to the next pack (or on
to loose objects).

Furthermore, we will cache the descriptor to the opened
packfile. Which means that later, when we actually try to
access the object, we are likely to still have that packfile
opened, and won't care if it has been unlinked from the
filesystem.

Notice the "likely" above. If there is another pack access
in the interim, and we run out of descriptors, we could
close the pack. And then a later attempt to access the
closed pack could fail (we'll try to re-open it, of course,
but it may have been deleted). In practice, this doesn't
happen because we tend to look up items and then access them
immediately.

Pack-objects does not follow this code path. Instead, it
accesses the packs at a much lower level, using
find_pack_entry_one directly. This means we skip the
is_pack_valid check, and may end up with the name of a
packfile, but no open descriptor.

We can add the same is_pack_valid check here. Unfortunately,
the access patterns of pack-objects are not quite as nice
for keeping lookup and object access together. We look up
each object as we find out about it, and the only later when
writing the packfile do we necessarily access it. Which
means that the opened packfile may be closed in the interim.

In practice, however, adding this check still has value, for
three reasons.

  1. If you have a reasonable number of packs and/or a
     reasonable file descriptor limit, you can keep all of
     your packs open simultaneously. If this is the case,
     then the race is impossible to trigger.

  2. Even if you can't keep all packs open at once, you
     may end up keeping the deleted one open (i.e., you may
     get lucky).

  3. The race window is shortened. You may notice early that
     the pack is gone, and not try to access it. Triggering
     the problem without this check means deleting the pack
     any time after we read the list of index files, but
     before we access the looked-up objects.  Triggering it
     with this check means deleting the pack means deleting
     the pack after we do a lookup (and successfully access
     the packfile), but before we access the object. Which
     is a smaller window.

Acked-by: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2011-10-14 11:42:37 -07:00
Junio C Hamano 2e2e7e9dd0 Merge branch 'jc/fetch-verify'
* jc/fetch-verify:
  fetch: verify we have everything we need before updating our ref
  rev-list --verify-object
  list-objects: pass callback data to show_objects()
2011-10-05 12:36:20 -07:00
Junio C Hamano 4947367267 list-objects: pass callback data to show_objects()
The traverse_commit_list() API takes two callback functions, one to show
commit objects, and the other to show other kinds of objects. Even though
the former has a callback data parameter, so that the callback does not
have to rely on global state, the latter does not.

Give the show_objects() callback the same callback data parameter.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2011-09-01 15:46:12 -07:00
Junio C Hamano 324b6b1678 Merge branch 'mh/check-attr-relative'
* mh/check-attr-relative: (29 commits)
  test-path-utils: Add subcommand "prefix_path"
  test-path-utils: Add subcommand "absolute_path"
  git-check-attr: Normalize paths
  git-check-attr: Demonstrate problems with relative paths
  git-check-attr: Demonstrate problems with unnormalized paths
  git-check-attr: test that no output is written to stderr
  Rename git_checkattr() to git_check_attr()
  git-check-attr: Fix command-line handling to match docs
  git-check-attr: Drive two tests using the same raw data
  git-check-attr: Add an --all option to show all attributes
  git-check-attr: Error out if no pathnames are specified
  git-check-attr: Process command-line args more systematically
  git-check-attr: Handle each error separately
  git-check-attr: Extract a function error_with_usage()
  git-check-attr: Introduce a new variable
  git-check-attr: Extract a function output_attr()
  Allow querying all attributes on a file
  Remove redundant check
  Remove redundant call to bootstrap_attr_stack()
  Extract a function collect_all_attrs()
  ...
2011-08-17 17:36:22 -07:00
Junio C Hamano 96790ca029 Merge branch 'jc/pack-order-tweak'
* jc/pack-order-tweak:
  pack-objects: optimize "recency order"
  core: log offset pack data accesses happened
2011-08-05 14:54:57 -07:00
Michael Haggerty d932f4eb9f Rename git_checkattr() to git_check_attr()
Suggested by: Junio Hamano <gitster@pobox.com>

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2011-08-04 15:53:21 -07:00
Junio C Hamano d907bf8ef3 Merge branch 'jc/index-pack'
* jc/index-pack:
  verify-pack: use index-pack --verify
  index-pack: show histogram when emulating "verify-pack -v"
  index-pack: start learning to emulate "verify-pack -v"
  index-pack: a miniscule refactor
  index-pack --verify: read anomalous offsets from v2 idx file
  write_idx_file: need_large_offset() helper function
  index-pack: --verify
  write_idx_file: introduce a struct to hold idx customization options
  index-pack: group the delta-base array entries also by type

Conflicts:
	builtin/verify-pack.c
	cache.h
	sha1_file.c
2011-07-19 09:54:51 -07:00
Junio C Hamano 1b4bb16b9e pack-objects: optimize "recency order"
This optimizes the "recency order" (see pack-heuristics.txt in
Documentation/technical/ directory) used to order objects within a
packfile in three ways:

 - Commits at the tip of tags are written together, in the hope that
   revision traversal done in incremental fetch (which starts by
   putting them in a revision queue marked as UNINTERESTING) will see a
   better locality of these objects;

 - In the original recency order, trees and blobs are intermixed. Write
   trees together before blobs, in the hope that this will improve
   locality when running pathspec-limited revision traversal, i.e.
   "git log paths...";

 - When writing blob objects out, write the whole family of blobs that use
   the same delta base object together, by starting from the root of the
   delta chain, and writing its immediate children in a width-first
   manner, in the hope that this will again improve locality when reading
   blobs that belong to the same path, which are likely to be deltified
   against each other.

I tried various workloads in the Linux kernel repositories (HEAD at
v3.0-rc6-71-g4dd1b49) packed with v1.7.6 and with this patch, counting how
large seeks are needed between adjacent accesses to objects in the pack,
and the result looks promising.  The history has 2072052 objects, weighing
some 490MiB.

 * Simple commit-only log.

   $ git log >/dev/null

   There are 254656 commits in total.

                                  v1.7.6  with patch
   Total number of access :      258,031     258,032
          0.0% percentile :           12          12
         10.0% percentile :          259         259
         20.0% percentile :          294         294
         30.0% percentile :          326         326
         40.0% percentile :          363         363
         50.0% percentile :          415         415
         60.0% percentile :          513         513
         70.0% percentile :          857         858
         80.0% percentile :       10,434      10,441
         90.0% percentile :       91,985      91,996
         95.0% percentile :      260,852     260,885
         99.0% percentile :    1,150,680   1,152,811
         99.9% percentile :    3,148,435   3,148,435
       Less than 2MiB seek:       99.70%      99.69%

   95% of the pack accesses look at data that is no further than 260kB
   from the previous location we accessed. The patch does not change the
   order of commit objects very much, and the result is very similar.

 * Pathspec-limited log.

   $ git log drivers/net >/dev/null

   The path is touched by 26551 commits and merges (among 254656 total).

                                  v1.7.6  with patch
   Total number of access :      559,511     558,663
          0.0% percentile :            0           0
         10.0% percentile :          182         167
         20.0% percentile :          259         233
         30.0% percentile :          357         304
         40.0% percentile :          714         485
         50.0% percentile :        5,046       3,976
         60.0% percentile :      688,671     443,578
         70.0% percentile :  319,574,732 110,370,100
         80.0% percentile :  361,647,599 123,707,229
         90.0% percentile :  393,195,669 128,947,636
         95.0% percentile :  405,496,875 131,609,321
         99.0% percentile :  412,942,470 133,078,115
         99.5% percentile :  413,172,266 133,163,349
         99.9% percentile :  413,354,356 133,240,445
       Less than 2MiB seek:       61.71%      62.87%

   With the current pack heuristics, more than 30% of accesses have to
   seek further than 300MB; the updated pack heuristics ensures that less
   than 0.1% of accesses have to seek further than 135MB. This is largely
   due to the fact that the updated heuristics does not mix blobs and
   trees together.

 * Blame.

   $ git blame drivers/net/ne.c >/dev/null

   The path is touched by 34 commits and merges.

                                  v1.7.6  with patch
   Total number of access :      178,147     178,166
          0.0% percentile :            0           0
         10.0% percentile :          142         139
         20.0% percentile :          222         194
         30.0% percentile :          373         300
         40.0% percentile :        1,168         837
         50.0% percentile :       11,248       7,334
         60.0% percentile :  305,121,284 106,850,130
         70.0% percentile :  361,427,854 123,709,715
         80.0% percentile :  388,127,343 128,171,047
         90.0% percentile :  399,987,762 130,200,707
         95.0% percentile :  408,230,673 132,174,308
         99.0% percentile :  412,947,017 133,181,160
         99.5% percentile :  413,312,798 133,220,425
         99.9% percentile :  413,352,366 133,269,051
       Less than 2MiB seek:       56.47%      56.83%

   The result is very similar to the pathspec-limited log above, which
   only looks at the tree objects.

 * Packing recent history.

   $ (git for-each-ref --format='^%(refname)' refs/tags; echo HEAD) |
     git pack-objects --revs --stdout >/dev/null

   This should pack data worth 71 commits.

                                  v1.7.6  with patch
   Total number of access :       11,511      11,514
          0.0% percentile :            0           0
         10.0% percentile :           48          47
         20.0% percentile :          134          98
         30.0% percentile :          332         178
         40.0% percentile :        1,386         293
         50.0% percentile :        8,030         478
         60.0% percentile :       33,676       1,195
         70.0% percentile :      147,268      26,216
         80.0% percentile :    9,178,662     464,598
         90.0% percentile :   67,922,665     965,782
         95.0% percentile :   87,773,251   1,226,102
         99.0% percentile :   98,011,763   1,932,377
         99.5% percentile :  100,074,427  33,642,128
         99.9% percentile :  105,336,398 275,772,650
       Less than 2MiB seek:       77.09%      99.04%

    The long-tail part of the result looks worse with the patch, but
    the change helps majority of the access. 99.04% of the accesses
    need less than 2MiB of seeking, compared to 77.09% with the current
    packing heuristics.

 * Index pack.

   $ git index-pack -v .git/objects/pack/pack*.pack

                                  v1.7.6  with patch
   Total number of access :    2,791,228   2,788,802
          0.0% percentile :            9           9
         10.0% percentile :          140          89
         20.0% percentile :          233         167
         30.0% percentile :          322         235
         40.0% percentile :          464         310
         50.0% percentile :          862         423
         60.0% percentile :        2,566         686
         70.0% percentile :       25,827       1,498
         80.0% percentile :    1,317,862       4,971
         90.0% percentile :   11,926,385     119,398
         95.0% percentile :   41,304,149     952,519
         99.0% percentile :  227,613,070   6,709,650
         99.5% percentile :  321,265,121  11,734,871
         99.9% percentile :  382,919,785  33,155,191
       Less than 2MiB seek:       81.73%      96.92%

   As the index-pack command already walks objects in the delta chain
   order, writing the blobs out in the delta chain order seems to
   drastically improve the locality of access.

Note that a half-a-gigabyte packfile comfortably fits in the buffer cache,
and you would unlikely to see much performance difference on a modern and
reasonably beefy machine with enough memory and local disks. Benchmarking
with cold cache (or over NFS) would be interesting.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2011-07-08 10:03:24 -07:00
Junio C Hamano ef49a7a012 zlib: zlib can only process 4GB at a time
The size of objects we read from the repository and data we try to put
into the repository are represented in "unsigned long", so that on larger
architectures we can handle objects that weigh more than 4GB.

But the interface defined in zlib.h to communicate with inflate/deflate
limits avail_in (how many bytes of input are we calling zlib with) and
avail_out (how many bytes of output from zlib are we ready to accept)
fields effectively to 4GB by defining their type to be uInt.

In many places in our code, we allocate a large buffer (e.g. mmap'ing a
large loose object file) and tell zlib its size by assigning the size to
avail_in field of the stream, but that will truncate the high octets of
the real size. The worst part of this story is that we often pass around
z_stream (the state object used by zlib) to keep track of the number of
used bytes in input/output buffer by inspecting these two fields, which
practically limits our callchain to the same 4GB limit.

Wrap z_stream in another structure git_zstream that can express avail_in
and avail_out in unsigned long. For now, just die() when the caller gives
a size that cannot be given to a single zlib call. In later patches in the
series, we would make git_inflate() and git_deflate() internally loop to
give callers an illusion that our "improved" version of zlib interface can
operate on a buffer larger than 4GB in one go.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2011-06-10 11:52:15 -07:00
Junio C Hamano 225a6f1068 zlib: wrap deflateBound() too
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2011-06-10 11:18:17 -07:00
Junio C Hamano 55bb5c9147 zlib: wrap deflate side of the API
Wrap deflateInit, deflate, and deflateEnd for everybody, and the sole use
of deflateInit2 in remote-curl.c to tell the library to use gzip header
and trailer in git_deflate_init_gzip().

There is only one caller that cares about the status from deflateEnd().
Introduce git_deflate_end_gently() to let that sole caller retrieve the
status and act on it (i.e. die) for now, but we would probably want to
make inflate_end/deflate_end die when they ran out of memory and get
rid of the _gently() kind.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2011-06-10 11:10:29 -07:00
Junio C Hamano 15366280c2 Teach core.bigfilethreashold to pack-objects
The pack-objects command should take notice of the object file and
refrain from attempting to delta large ones, to be consistent with
the fast-import command.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2011-04-05 20:25:49 -07:00
Junio C Hamano ebcfb3791a write_idx_file: introduce a struct to hold idx customization options
Remove two globals, pack_idx_default version and pack_idx_off32_limit,
and place them in a pack_idx_option structure.  Allow callers to pass
it to write_idx_file() as a parameter.

Adjust all callers to the API change.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2011-02-27 23:29:03 -08:00
Junio C Hamano b361888dd5 thread-utils.h: simplify the inclusion
All files that include this header file use the same four line
incantation:

    #ifndef NO_PTHREADS
    #include <pthread.h>
    #include "thread-utils.h"
    #endif

Move the responsibility for that gymnastics to the header file from the
files that include it.  This approach makes it easier to later declare new
services that are related to threading in thread-utils.h and have them
available to all the threading code.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2010-12-10 12:58:06 -08:00
Junio C Hamano 39f04dbaac Merge branch 'jn/thinner-wrapper'
* jn/thinner-wrapper:
  Remove pack file handling dependency from wrapper.o
  pack-objects: mark file-local variable static
  wrapper: give zlib wrappers their own translation unit
  strbuf: move strbuf_branchname to sha1_name.c
  path helpers: move git_mkstemp* to wrapper.c
  wrapper: move odb_* to environment.c
  wrapper: move xmmap() to sha1_file.c
2010-12-03 16:13:06 -08:00
Jonathan Nieder bc9b21755e pack-objects: mark file-local variable static
old_try_to_free_routine is not meant for use from other files.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2010-11-10 11:08:04 -08:00
Nicolas Pitre 71064a956b make pack-objects a bit more resilient to repo corruption
Right now, packing valid objects could fail when creating a thin pack
simply because a pack edge object used as a preferred base is corrupted.
Since preferred base objects are not strictly needed to produce a valid
pack, let's not consider the inability to read them as a fatal error.
Delta compression may well be attempted against other objects in the
search window.  To avoid warning storms (we are in the inner loop of
the delta search window) a warning is emitted only on the first
occurrence.

Signed-off-by: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2010-10-22 14:59:58 -07:00
Štěpán Němec 884220653f Put a space between `<' and argument in pack-objects usage string
This makes it cosistent with other places (including the
git-pack-objects(1) manpage itself) and avoids possible confusion (I,
for one, mistook `<object-list' for a `<object-list>' typo at first when
preparing this series).

Signed-off-by: Štěpán Němec <stepnem@gmail.com>
Acked-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2010-10-08 12:31:08 -07:00
Štěpán Němec 0adda9362a Use parentheses and `...' where appropriate
Remove some stray usage of other bracket types and asterisks for the
same purpose.

Signed-off-by: Štěpán Němec <stepnem@gmail.com>
Acked-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2010-10-08 12:31:07 -07:00
Štěpán Němec 62b4698e55 Use angles for placeholders consistently
Signed-off-by: Štěpán Němec <stepnem@gmail.com>
Acked-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2010-10-08 12:29:52 -07:00
Erik Faye-Lund c03c83152d do not depend on signed integer overflow
Signed integer overflow is not defined in C, so do not depend on it.

This fixes a problem with GCC 4.4.0 and -O3 where the optimizer would
consider "consumed_bytes > consumed_bytes + bytes" as a constant
expression, and never execute the die()-call.

Signed-off-by: Erik Faye-Lund <kusmabite@gmail.com>
Acked-by: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2010-10-06 11:10:07 -07:00