Mercurial > hg
view tests/test-largefiles-small-disk.t @ 17970:0b03454abae7
ancestor: faster algorithm for difference of ancestor sets
One of the major reasons rebase is slow in large repositories is
the computation of the detach set: the set of ancestors of the
changesets to rebase not in the destination parent. This is currently
done via a revset that does two walks all the way to the root of
the DAG. Instead of doing that, to find ancestors of a set <revs>
not in another set <common> we walk up the tree in reverse revision
number order, maintaining sets of nodes visited from <revs>, <common>
or both.
For the common case where the sets are close both topologically and
in revision number (relative to repository size), this has been
found to speed up rebase by around 15-20%. When the nodes are farther
apart and the DAG is highly branching, it is harder to say which
would win.
Here's how long computing the detach set takes in a linear repository
with over 400000 changesets, rebasing near tip:
Rebasing across 4 changesets
Revset method: 2.2s
New algorithm: 0.00015s
Rebasing across 250 changesets
Revset method: 2.2s
New algorithm: 0.00069s
Rebasing across 10000 changesets
Revset method: 2.4s
New algorithm: 0.019s
author | Siddharth Agarwal <sid0@fb.com> |
---|---|
date | Mon, 26 Nov 2012 11:46:51 -0800 |
parents | 0d91211dd12f |
children | c9db897d5a43 |
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Test how largefiles abort in case the disk runs full $ cat > criple.py <<EOF > import os, errno, shutil > from mercurial import util > # > # this makes the original largefiles code abort: > def copyfileobj(fsrc, fdst, length=16*1024): > fdst.write(fsrc.read(4)) > raise IOError(errno.ENOSPC, os.strerror(errno.ENOSPC)) > shutil.copyfileobj = copyfileobj > # > # this makes the rewritten code abort: > def filechunkiter(f, size=65536, limit=None): > yield f.read(4) > raise IOError(errno.ENOSPC, os.strerror(errno.ENOSPC)) > util.filechunkiter = filechunkiter > # > def oslink(src, dest): > raise OSError("no hardlinks, try copying instead") > util.oslink = oslink > EOF $ echo "[extensions]" >> $HGRCPATH $ echo "largefiles =" >> $HGRCPATH $ hg init alice $ cd alice $ echo "this is a very big file" > big $ hg add --large big $ hg commit --config extensions.criple=$TESTTMP/criple.py -m big abort: No space left on device [255] The largefile is not created in .hg/largefiles: $ ls .hg/largefiles dirstate The user cache is not even created: >>> import os; os.path.exists("$HOME/.cache/largefiles/") False Make the commit with space on the device: $ hg commit -m big Now make a clone with a full disk, and make sure lfutil.link function makes copies instead of hardlinks: $ cd .. $ hg --config extensions.criple=$TESTTMP/criple.py clone --pull alice bob requesting all changes adding changesets adding manifests adding file changes added 1 changesets with 1 changes to 1 files updating to branch default 1 files updated, 0 files merged, 0 files removed, 0 files unresolved getting changed largefiles abort: No space left on device [255] The largefile is not created in .hg/largefiles: $ ls bob/.hg/largefiles