git/list-objects.c, branch v2.4.2

rev-list: add an option to mark fewer edges as uninteresting

2014-12-29T17:57:55Z

In commit fbd4a70 (list-objects: mark more commits as edges in mark_edges_uninteresting - 2013-08-16), we marked an increasing number of edges uninteresting. This change, and the subsequent change to make this conditional on --objects-edge, are used by --thin to make much smaller packs for shallow clones. Unfortunately, they cause a significant performance regression when pushing non-shallow clones with lots of refs (23.322 seconds vs. 4.785 seconds with 22400 refs). Add an option to git rev-list, --objects-edge-aggressive, that preserves this more aggressive behavior, while leaving --objects-edge to provide more performant behavior. Preserve the current behavior for the moment by using the aggressive option. Signed-off-by: brian m. carlson Signed-off-by: Junio C Hamano

traverse_commit_list: support pending blobs/trees with paths

2014-10-19T22:06:31Z

When we call traverse_commit_list, we may have trees and blobs in the pending array. As we process these, we pass the "name" field from the pending entry as the path of the object within the tree (which then becomes the root path if we recurse into subtrees). When we set up the traversal in prepare_revision_walk, though, the "name" field of any pending trees and blobs is likely to be the ref at which we found the object. We would not want to make this part of the path (e.g., doing so would make "git rev-list --objects v2.6.11-tree" in linux.git show paths like "v2.6.11-tree/Makefile", which is nonsensical). Therefore prepare_revision_walk sets the name field of each pending tree and blobs to the empty string. However, this leaves no room for a caller who does know the correct path of a pending object to propagate that information to the revision walker. We can fix this by making two related changes: 1. Use the "path" field as the path instead of the "name" field in traverse_commit_list. If the path is not set, default to "" (which is what we always ended up with in the current code, because of prepare_revision_walk). 2. In prepare_revision_walk, make a complete copy of the entry. This makes the path field available to the walker (if there is one), solving our problem. Leaving the name field intact is now OK, as we do not use it as a path due to point (1) above (and we can use it to make more meaningful error messages if we want). We also make the original "mode" field available to the walker, though it does not actually use it. Note that we still re-add the pending objects and free the old ones (so we may strdup the path and name only to free the old ones). This could be made more efficient by simply copying the object_array entries that we are keeping. However, that would require more restructuring of the code, and is not done here. Signed-off-by: Jeff King Signed-off-by: Junio C Hamano

object_array: add a "clear" function

2014-10-16T17:10:37Z

There's currently no easy way to free the memory associated with an object_array (and in most cases, we simply leak the memory in a rev_info's pending array). Let's provide a helper to make this easier to handle. We can make use of it in list-objects.c, which does the same thing by hand (but fails to free the "name" field of each entry, potentially leaking memory). Signed-off-by: Jeff King Signed-off-by: Junio C Hamano

Merge branch 'jk/pack-bitmap'

2014-04-08T19:00:33Z

* jk/pack-bitmap: pack-objects: do not reuse packfiles without --delta-base-offset add `ignore_missing_links` mode to revwalk

add `ignore_missing_links` mode to revwalk

2014-04-04T20:31:38Z

When pack-objects is computing the reachability bitmap to serve a fetch request, it can erroneously die() if some of the UNINTERESTING objects are not present. Upload-pack throws away HAVE lines from the client for objects we do not have, but we may have a tip object without all of its ancestors (e.g., if the tip is no longer reachable and was new enough to survive a `git prune`, but some of its reachable objects did get pruned). In the non-bitmap case, we do a revision walk with the HAVE objects marked as UNINTERESTING. The revision walker explicitly ignores errors in accessing UNINTERESTING commits to handle this case (and we do not bother looking at UNINTERESTING trees or blobs at all). When we have bitmaps, however, the process is quite different. The bitmap index for a pack-objects run is calculated in two separate steps: First, we perform an extensive walk from all the HAVEs to find the full set of objects reachable from them. This walk is usually optimized away because we are expected to hit an object with a bitmap during the traversal, which allows us to terminate early. Secondly, we perform an extensive walk from all the WANTs, which usually also terminates early because we hit a commit with an existing bitmap. Once we have the resulting bitmaps from the two walks, we AND-NOT them together to obtain the resulting set of objects we need to pack. When we are walking the HAVE objects, the revision walker does not know that we are walking it only to mark the results as uninteresting. We strip out the UNINTERESTING flag, because those objects _are_ interesting to us during the first walk. We want to keep going to get a complete set of reachable objects if we can. We need some way to tell the revision walker that it's OK to silently truncate the HAVE walk, just like it does for the UNINTERESTING case. This patch introduces a new `ignore_missing_links` flag to the `rev_info` struct, which we set only for the HAVE walk. It also adds tests to cover UNINTERESTING objects missing from several positions: a missing blob, a missing tree, and a missing parent commit. The missing blob already worked (as we do not care about its contents at all), but the other two cases caused us to die(). Note that there are a few cases we do not need to test: 1. We do not need to test a missing tree, with the blob still present. Without the tree that refers to it, we would not know that the blob is relevant to our walk. 2. We do not need to test a tip commit that is missing. Upload-pack omits these for us (and in fact, we complain even in the non-bitmap case if it fails to do so). Reported-by: Siddharth Agarwal Signed-off-by: Vicent Marti Signed-off-by: Jeff King Signed-off-by: Junio C Hamano

Merge branch 'jk/mark-edges-uninteresting'

2014-01-27T18:45:08Z

Fix performance regression in v1.8.4.x and later. * jk/mark-edges-uninteresting: list-objects: only look at cmdline trees with edge_hint t/perf: time rev-list with UNINTERESTING commits

list-objects: only look at cmdline trees with edge_hint

2014-01-21T22:46:24Z

When rev-list is given a command-line like: git rev-list --objects $commit --not --all the most accurate answer is the difference between the set of objects reachable from $commit and the set reachable from all of the existing refs. However, we have not historically provided that answer, because it is very expensive to calculate. We would have to open every tree of every commit in the entire history. Instead, we find the accurate set difference of the reachable commits, and then mark the trees at the boundaries as uninteresting. This misses objects which appear in the trees of both the interesting commits and deep within the uninteresting history. Commit fbd4a70 (list-objects: mark more commits as edges in mark_edges_uninteresting, 2013-08-16) noticed that we miss those objects during pack-objects, and added code to examine the trees of all of the "--not" refs given on the command-line. Note that this is still not the complete set difference, because we look only at the tips of the command-line arguments, not all of their reachable commits. But it increases the set of boundary objects we consider, which is especially important for shallow fetches. So we are trading extra CPU time for a larger set of boundary objects, which can improve the resulting pack size for a --thin pack. This tradeoff probably makes sense in the context of pack-objects, where we have set revs->edge_hint to have the traversal feed us the set of boundary objects. For a regular rev-list, though, it is probably not a good tradeoff. It is true that it makes our list slightly closer to a true set difference, but it is a rare case where this is important. And because we do not have revs->edge_hint set, we do nothing useful with the larger set of boundary objects. This patch therefore ties the extra tree examination to the revs->edge_hint flag; it is the presence of that flag that makes the tradeoff worthwhile. Here is output from the p0001-rev-list showing the improvement in performance: Test HEAD^ HEAD ----------------------------------------------------------------------------------------- 0001.1: rev-list --all 0.69(0.65+0.02) 0.69(0.66+0.02) +0.0% 0001.2: rev-list --all --objects 3.22(3.19+0.03) 3.23(3.20+0.03) +0.3% 0001.4: rev-list $commit --not --all 0.04(0.04+0.00) 0.04(0.04+0.00) +0.0% 0001.5: rev-list --objects $commit --not --all 0.27(0.26+0.01) 0.04(0.04+0.00) -85.2% Signed-off-by: Jeff King Signed-off-by: Junio C Hamano

Merge branch 'nd/fetch-into-shallow'

2013-09-20T19:25:32Z

When there is no sufficient overlap between old and new history during a fetch into a shallow repository, we unnecessarily sent objects the sending side knows the receiving end has. * nd/fetch-into-shallow: Add testcase for needless objects during a shallow fetch list-objects: mark more commits as edges in mark_edges_uninteresting list-objects: reduce one argument in mark_edges_uninteresting upload-pack: delegate rev walking in shallow fetch to pack-objects shallow: add setup_temporary_shallow() shallow: only add shallow graft points to new shallow file move setup_alternate_shallow and write_shallow_commits to shallow.c

list-objects: mark more commits as edges in mark_edges_uninteresting

2013-08-28T18:54:18Z

The purpose of edge commits is to let pack-objects know what objects it can use as base, but does not need to include in the thin pack because the other side is supposed to already have them. So far we mark uninteresting parents of interesting commits as edges. But even an unrelated uninteresting commit (that the other side has) may become a good base for pack-objects and help produce more efficient packs. This is especially true for shallow clone, when the client issues a fetch with a depth smaller or equal to the number of commits the server is ahead of the client. For example, in this commit history the client has up to "A" and the server has up to "B": -------A---B have--^ ^ / want--+ If depth 1 is requested, the commit list to send to the client includes only B. The way m_e_u is working, it checks if parent commits of B are uninteresting, if so mark them as edges. Due to shallow effect, commit B is grafted to have no parents and the revision walker never sees A as the parent of B. In fact it marks no edges at all in this simple case and sends everything B has to the client even if it could have excluded what A and also the client already have. In a slightly different case where A is not a direct parent of B (iow there are commits in between A and B), marking A as an edge can still save some because B may still have stuff from the far ancestor A. There is another case from the earlier patch, when we deepen a ref from C->E to A->E: ---A---B C---D---E want--^ ^ ^ shallow-+ / have-------+ In this case we need to send A and B to the client, and C (i.e. the current shallow point that the client informs the server) is a very good base because it's closet to A and B. Normal m_e_u won't recognize C as an edge because it only looks back to parents (i.e. A<-B) not the opposite way B->C even if C is already marked as uninteresting commit by the previous patch. This patch includes all uninteresting commits from command line as edges and lets pack-objects decide what's best to do. The upside is we have better chance of producing better packs in certain cases. The downside is we may need to process some extra objects on the server side. For the shallow case on git.git, when the client is 5 commits behind and does "fetch --depth=3", the result pack is 99.26 KiB instead of 4.92 MiB. Reported-and-analyzed-by: Matthijs Kooijman Signed-off-by: Nguyễn Thái Ngọc Duy Signed-off-by: Junio C Hamano

list-objects: reduce one argument in mark_edges_uninteresting

2013-08-28T18:54:18Z

mark_edges_uninteresting() is always called with this form mark_edges_uninteresting(revs->commits, revs, ...); Remove the first argument and let mark_edges_uninteresting figure that out by itself. It helps answer the question "are this commit list and revs related in any way?" when looking at mark_edges_uninteresting implementation. Signed-off-by: Nguyễn Thái Ngọc Duy Signed-off-by: Junio C Hamano