Mercurial > hg
view mercurial/peer.py @ 26379:39d643252b9f
revlog: use existing file handle when reading during _addrevision
_addrevision() may need to read from revlogs as part of computing
deltas. Previously, we would flush existing file handles and open
a new, short-lived file handle to perform the reading.
If we have an existing file handle, it seems logical to reuse it
for reading instead of opening a new file handle. This patch
makes that the new behavior.
After this patch, revlog files are only reopened when adding
revisions if the revlog is switched from inline to non-inline.
On Linux when unbundling a bundle of the mozilla-central repo, this
patch has the following impact on system call counts:
Call Before After Delta
write 827,639 673,390 -154,249
open 700,103 684,089 -16,014
read 74,489 74,489 0
fstat 493,924 461,896 -32,028
close 249,131 233,117 -16,014
stat 242,001 242,001 0
lstat 18,676 18,676 0
lseek 20,268 20,268 0
ioctl 14,652 13,173 -1,479
TOTAL 3,180,758 2,930,679 -250,079
It's worth noting that many of the open() calls fail due to missing
files. That's why there are many more open() calls than close().
Despite the significant system call reduction, this change does not
seem to have a significant performance impact on Linux.
On Windows 10 (not a VM, on a SSD), this patch appears to reduce
unbundle time for mozilla-central from ~960s to ~920s. This isn't
as significant as I was hoping. But a decrease it is nonetheless.
Still, Windows unbundle performance is still >2x slower than Linux.
Despite the lack of significant gains, fewer system calls is fewer
system calls. If nothing else, this will narrow the focus of potential
areas to optimize in the future.
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Sun, 27 Sep 2015 16:08:18 -0700 |
parents | e6b56b2c1f26 |
children | d549cbb5503d |
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# peer.py - repository base classes for mercurial # # Copyright 2005, 2006 Matt Mackall <mpm@selenic.com> # Copyright 2006 Vadim Gelfer <vadim.gelfer@gmail.com> # # This software may be used and distributed according to the terms of the # GNU General Public License version 2 or any later version. from __future__ import absolute_import from .i18n import _ from . import ( error, util, ) # abstract batching support class future(object): '''placeholder for a value to be set later''' def set(self, value): if util.safehasattr(self, 'value'): raise error.RepoError("future is already set") self.value = value class batcher(object): '''base class for batches of commands submittable in a single request All methods invoked on instances of this class are simply queued and return a a future for the result. Once you call submit(), all the queued calls are performed and the results set in their respective futures. ''' def __init__(self): self.calls = [] def __getattr__(self, name): def call(*args, **opts): resref = future() self.calls.append((name, args, opts, resref,)) return resref return call def submit(self): pass class localbatch(batcher): '''performs the queued calls directly''' def __init__(self, local): batcher.__init__(self) self.local = local def submit(self): for name, args, opts, resref in self.calls: resref.set(getattr(self.local, name)(*args, **opts)) def batchable(f): '''annotation for batchable methods Such methods must implement a coroutine as follows: @batchable def sample(self, one, two=None): # Handle locally computable results first: if not one: yield "a local result", None # Build list of encoded arguments suitable for your wire protocol: encargs = [('one', encode(one),), ('two', encode(two),)] # Create future for injection of encoded result: encresref = future() # Return encoded arguments and future: yield encargs, encresref # Assuming the future to be filled with the result from the batched # request now. Decode it: yield decode(encresref.value) The decorator returns a function which wraps this coroutine as a plain method, but adds the original method as an attribute called "batchable", which is used by remotebatch to split the call into separate encoding and decoding phases. ''' def plain(*args, **opts): batchable = f(*args, **opts) encargsorres, encresref = batchable.next() if not encresref: return encargsorres # a local result in this case self = args[0] encresref.set(self._submitone(f.func_name, encargsorres)) return batchable.next() setattr(plain, 'batchable', f) return plain class peerrepository(object): def batch(self): return localbatch(self) def capable(self, name): '''tell whether repo supports named capability. return False if not supported. if boolean capability, return True. if string capability, return string.''' caps = self._capabilities() if name in caps: return True name_eq = name + '=' for cap in caps: if cap.startswith(name_eq): return cap[len(name_eq):] return False def requirecap(self, name, purpose): '''raise an exception if the given capability is not present''' if not self.capable(name): raise error.CapabilityError( _('cannot %s; remote repository does not ' 'support the %r capability') % (purpose, name)) def local(self): '''return peer as a localrepo, or None''' return None def peer(self): return self def canpush(self): return True def close(self): pass