view hgweb.cgi @ 39560:84bf6ded9317

wireprotoframing: buffer emitted data to reduce frame count

An upcoming commit introduces a wire protocol command that can emit
hundreds of thousands of small objects. Without a buffering layer,
we would emit a single, small frame for every object. Performance
profiling revealed this to be a source of significant overhead for
both client and server.

This commit introduces a very crude buffering layer so that we emit
fewer, bigger frames in such a scenario. This code will likely get
rewritten in the future to be part of the streams API, as we'll
need a similar strategy for compressing data. I don't want to think
about it too much at the moment though.

server
before: user 32.500+0.000 sys 1.160+0.000
after:  user 20.230+0.010 sys 0.180+0.000

client
before: user 133.400+0.000 sys 93.120+0.000
after:  user  68.370+0.000 sys 32.950+0.000

This appears to indicate we have significant overhead in the frame
processing code on both client and server. It might be worth profiling
that at some point...

Differential Revision: https://phab.mercurial-scm.org/D4473

#!/usr/bin/env python
#
# An example hgweb CGI script, edit as necessary
# See also https://mercurial-scm.org/wiki/PublishingRepositories

# Path to repo or hgweb config to serve (see 'hg help hgweb')
config = "/path/to/repo/or/config"

# Uncomment and adjust if Mercurial is not installed system-wide
# (consult "installed modules" path from 'hg debuginstall'):
#import sys; sys.path.insert(0, "/path/to/python/lib")

# Uncomment to send python tracebacks to the browser if an error occurs:
#import cgitb; cgitb.enable()

from mercurial import demandimport; demandimport.enable()
from mercurial.hgweb import hgweb, wsgicgi
application = hgweb(config)
wsgicgi.launch(application)