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.
#require serve
Test raw style of hgweb
$ hg init test
$ cd test
$ mkdir sub
$ cat >'sub/some text%.txt' <<ENDSOME
> This is just some random text
> that will go inside the file and take a few lines.
> It is very boring to read, but computers don't
> care about things like that.
> ENDSOME
$ hg add 'sub/some text%.txt'
$ hg commit -d "1 0" -m "Just some text"
$ hg serve -p $HGPORT -A access.log -E error.log -d --pid-file=hg.pid
$ cat hg.pid >> $DAEMON_PIDS
$ (get-with-headers.py localhost:$HGPORT '?f=bf0ff59095c9;file=sub/some%20text%25.txt;style=raw' content-type content-length content-disposition) >getoutput.txt
$ killdaemons.py hg.pid
$ cat getoutput.txt
200 Script output follows
content-type: application/binary
content-length: 157
content-disposition: inline; filename="some text%.txt"
This is just some random text
that will go inside the file and take a few lines.
It is very boring to read, but computers don't
care about things like that.
$ cat access.log error.log
127.0.0.1 - - [*] "GET /?f=bf0ff59095c9;file=sub/some%20text%25.txt;style=raw HTTP/1.1" 200 - (glob)
$ rm access.log error.log
$ hg serve -p $HGPORT -A access.log -E error.log -d --pid-file=hg.pid \
> --config web.guessmime=True
$ cat hg.pid >> $DAEMON_PIDS
$ (get-with-headers.py localhost:$HGPORT '?f=bf0ff59095c9;file=sub/some%20text%25.txt;style=raw' content-type content-length content-disposition) >getoutput.txt
$ killdaemons.py hg.pid
$ cat getoutput.txt
200 Script output follows
content-type: text/plain; charset="ascii"
content-length: 157
content-disposition: inline; filename="some text%.txt"
This is just some random text
that will go inside the file and take a few lines.
It is very boring to read, but computers don't
care about things like that.
$ cat access.log error.log
127.0.0.1 - - [*] "GET /?f=bf0ff59095c9;file=sub/some%20text%25.txt;style=raw HTTP/1.1" 200 - (glob)
$ cd ..