streamclone: use backgroundfilecloser (
issue4889)
Closing files that have been appended to is slow on Windows/NTFS.
CloseHandle() calls on this platform often take 1-10ms - and that's
on my i7-6700K Skylake processor with a modern and fast SSD. Contrast
with other I/O operations, such as writing data, which take <100us.
This means that creating/appending thousands of files can add
significant overhead. For example, cloning mozilla-central creates
~232,000 revlog files. Assuming 1ms per CloseHandle(), that yields
232s (3:52) of wall time waiting for file closes!
The impact of this overhead can be measured most directly when applying
stream clone bundles. Applying these files is effectively uncompressing
a tar archive (read: it's very fast).
Using a RAM disk (read: no I/O wait), the difference in wall time for a
`hg debugapplystreamclonebundle` for a ~1731 MB mozilla-central bundle
between Windows and Linux from the same machine is drastic:
Linux: ~12.8s (128MB/s)
Windows: ~352.0s (4.7MB/s)
Windows is ~27.5x slower. Yikes!
After this patch:
Linux: ~12.8s (128MB/s)
Windows: ~102.1s (16.1MB/s)
Windows is now ~3.4x faster. Unfortunately, it is still ~8x slower than
Linux. Profiling reveals a few hot code paths that could likely be
improved. But those are for other patches.
This patch introduces test-clone-uncompressed.t because existing tests
of `clone --uncompressed` are scattered about and adding a variation for
background thread closing to e.g. test-http.t doesn't feel correct.
#!/bin/bash -eu
. $(dirname $0)/dockerlib.sh
. $(dirname $0)/packagelib.sh
BUILDDIR=$(dirname $0)
export ROOTDIR=$(cd $BUILDDIR/..; pwd)
checkdocker
DISTID="$1"
CODENAME="$2"
PLATFORM="$1-$2"
shift # extra params are passed to build process
OUTPUTDIR=${OUTPUTDIR:=$ROOTDIR/packages/$PLATFORM}
initcontainer $PLATFORM
# debuild only appears to be able to save built debs etc to .., so we
# have to share the .. of the current directory with the docker
# container and hope it's writable. Whee.
dn=$(basename $PWD)
if [ $(uname) = "Darwin" ] ; then
$DOCKER run -u $DBUILDUSER --rm -v $PWD/..:/mnt $CONTAINER \
sh -c "cd /mnt/$dn && make clean && make local"
fi
$DOCKER run -u $DBUILDUSER --rm -v $PWD/..:/mnt $CONTAINER \
sh -c "cd /mnt/$dn && DEB_BUILD_OPTIONS='${DEB_BUILD_OPTIONS:=}' contrib/builddeb --build --distid $DISTID --codename $CODENAME"
contrib/builddeb --cleanup --distid $DISTID --codename $CODENAME
if [ $(uname) = "Darwin" ] ; then
$DOCKER run -u $DBUILDUSER --rm -v $PWD/..:/mnt $CONTAINER \
sh -c "cd /mnt/$dn && make clean"
fi