Mercurial > hg
view hgext/censor.py @ 38732:be4984261611
merge: mark file gets as not thread safe (issue5933)
In default installs, this has the effect of disabling the thread-based
worker on Windows when manifesting files in the working directory. My
measurements have shown that with revlog-based repositories, Mercurial
spends a lot of CPU time in revlog code resolving file data. This ends
up incurring a lot of context switching across threads and slows down
`hg update` operations when going from an empty working directory to
the tip of the repo.
On mozilla-unified (246,351 files) on an i7-6700K (4+4 CPUs):
before: 487s wall
after: 360s wall (equivalent to worker.enabled=false)
cpus=2: 379s wall
Even with only 2 threads, the thread pool is still slower.
The introduction of the thread-based worker (02b36e860e0b) states that
it resulted in a "~50%" speedup for `hg sparse --enable-profile` and
`hg sparse --disable-profile`. This disagrees with my measurement
above. I theorize a few reasons for this:
1) Removal of files from the working directory is I/O - not CPU - bound
and should benefit from a thread pool (unless I/O is insanely fast
and the GIL release is near instantaneous). So tests like `hg sparse
--enable-profile` may exercise deletion throughput and aren't good
benchmarks for worker tasks that are CPU heavy.
2) The patch was authored by someone at Facebook. The results were
likely measured against a repository using remotefilelog. And I
believe that revision retrieval during working directory updates with
remotefilelog will often use a remote store, thus being I/O and not
CPU bound. This probably resulted in an overstated performance gain.
Since there appears to be a need to enable the thread-based worker with
some stores, I've made the flagging of file gets as thread safe
configurable. I've made it experimental because I don't want to formalize
a boolean flag for this option and because this attribute is best
captured against the store implementation. But we don't have a proper
store API for this yet. I'd rather cross this bridge later.
It is possible there are revlog-based repositories that do benefit from
a thread-based worker. I didn't do very comprehensive testing. If there
are, we may want to devise a more proper algorithm for whether to use
the thread-based worker, including possibly config options to limit the
number of threads to use. But until I see evidence that justifies
complexity, simplicity wins.
Differential Revision: https://phab.mercurial-scm.org/D3963
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Wed, 18 Jul 2018 09:49:34 -0700 |
parents | e219e355e088 |
children | e7aa113b14f7 |
line wrap: on
line source
# Copyright (C) 2015 - Mike Edgar <adgar@google.com> # # This extension enables removal of file content at a given revision, # rewriting the data/metadata of successive revisions to preserve revision log # integrity. """erase file content at a given revision The censor command instructs Mercurial to erase all content of a file at a given revision *without updating the changeset hash.* This allows existing history to remain valid while preventing future clones/pulls from receiving the erased data. Typical uses for censor are due to security or legal requirements, including:: * Passwords, private keys, cryptographic material * Licensed data/code/libraries for which the license has expired * Personally Identifiable Information or other private data Censored nodes can interrupt mercurial's typical operation whenever the excised data needs to be materialized. Some commands, like ``hg cat``/``hg revert``, simply fail when asked to produce censored data. Others, like ``hg verify`` and ``hg update``, must be capable of tolerating censored data to continue to function in a meaningful way. Such commands only tolerate censored file revisions if they are allowed by the "censor.policy=ignore" config option. """ from __future__ import absolute_import from mercurial.i18n import _ from mercurial.node import short from mercurial import ( error, registrar, revlog, scmutil, util, ) cmdtable = {} command = registrar.command(cmdtable) # Note for extension authors: ONLY specify testedwith = 'ships-with-hg-core' for # extensions which SHIP WITH MERCURIAL. Non-mainline extensions should # be specifying the version(s) of Mercurial they are tested with, or # leave the attribute unspecified. testedwith = 'ships-with-hg-core' @command('censor', [('r', 'rev', '', _('censor file from specified revision'), _('REV')), ('t', 'tombstone', '', _('replacement tombstone data'), _('TEXT'))], _('-r REV [-t TEXT] [FILE]')) def censor(ui, repo, path, rev='', tombstone='', **opts): with repo.wlock(), repo.lock(): return _docensor(ui, repo, path, rev, tombstone, **opts) def _docensor(ui, repo, path, rev='', tombstone='', **opts): if not path: raise error.Abort(_('must specify file path to censor')) if not rev: raise error.Abort(_('must specify revision to censor')) wctx = repo[None] m = scmutil.match(wctx, (path,)) if m.anypats() or len(m.files()) != 1: raise error.Abort(_('can only specify an explicit filename')) path = m.files()[0] flog = repo.file(path) if not len(flog): raise error.Abort(_('cannot censor file with no history')) rev = scmutil.revsingle(repo, rev, rev).rev() try: ctx = repo[rev] except KeyError: raise error.Abort(_('invalid revision identifier %s') % rev) try: fctx = ctx.filectx(path) except error.LookupError: raise error.Abort(_('file does not exist at revision %s') % rev) fnode = fctx.filenode() headctxs = [repo[c] for c in repo.heads()] heads = [c for c in headctxs if path in c and c.filenode(path) == fnode] if heads: headlist = ', '.join([short(c.node()) for c in heads]) raise error.Abort(_('cannot censor file in heads (%s)') % headlist, hint=_('clean/delete and commit first')) wp = wctx.parents() if ctx.node() in [p.node() for p in wp]: raise error.Abort(_('cannot censor working directory'), hint=_('clean/delete/update first')) flogv = flog.version & 0xFFFF if flogv != revlog.REVLOGV1: raise error.Abort( _('censor does not support revlog version %d') % (flogv,)) tombstone = revlog.packmeta({"censored": tombstone}, "") crev = fctx.filerev() if len(tombstone) > flog.rawsize(crev): raise error.Abort(_( 'censor tombstone must be no longer than censored data')) # Using two files instead of one makes it easy to rewrite entry-by-entry idxread = repo.svfs(flog.indexfile, 'r') idxwrite = repo.svfs(flog.indexfile, 'wb', atomictemp=True) if flog.version & revlog.FLAG_INLINE_DATA: dataread, datawrite = idxread, idxwrite else: dataread = repo.svfs(flog.datafile, 'r') datawrite = repo.svfs(flog.datafile, 'wb', atomictemp=True) # Copy all revlog data up to the entry to be censored. rio = revlog.revlogio() offset = flog.start(crev) for chunk in util.filechunkiter(idxread, limit=crev * rio.size): idxwrite.write(chunk) for chunk in util.filechunkiter(dataread, limit=offset): datawrite.write(chunk) def rewriteindex(r, newoffs, newdata=None): """Rewrite the index entry with a new data offset and optional new data. The newdata argument, if given, is a tuple of three positive integers: (new compressed, new uncompressed, added flag bits). """ offlags, comp, uncomp, base, link, p1, p2, nodeid = flog.index[r] flags = revlog.gettype(offlags) if newdata: comp, uncomp, nflags = newdata flags |= nflags offlags = revlog.offset_type(newoffs, flags) e = (offlags, comp, uncomp, r, link, p1, p2, nodeid) idxwrite.write(rio.packentry(e, None, flog.version, r)) idxread.seek(rio.size, 1) def rewrite(r, offs, data, nflags=revlog.REVIDX_DEFAULT_FLAGS): """Write the given full text to the filelog with the given data offset. Returns: The integer number of data bytes written, for tracking data offsets. """ flag, compdata = flog.compress(data) newcomp = len(flag) + len(compdata) rewriteindex(r, offs, (newcomp, len(data), nflags)) datawrite.write(flag) datawrite.write(compdata) dataread.seek(flog.length(r), 1) return newcomp # Rewrite censored revlog entry with (padded) tombstone data. pad = ' ' * (flog.rawsize(crev) - len(tombstone)) offset += rewrite(crev, offset, tombstone + pad, revlog.REVIDX_ISCENSORED) # Rewrite all following filelog revisions fixing up offsets and deltas. for srev in xrange(crev + 1, len(flog)): if crev in flog.parentrevs(srev): # Immediate children of censored node must be re-added as fulltext. try: revdata = flog.revision(srev) except error.CensoredNodeError as e: revdata = e.tombstone dlen = rewrite(srev, offset, revdata) else: # Copy any other revision data verbatim after fixing up the offset. rewriteindex(srev, offset) dlen = flog.length(srev) for chunk in util.filechunkiter(dataread, limit=dlen): datawrite.write(chunk) offset += dlen idxread.close() idxwrite.close() if dataread is not idxread: dataread.close() datawrite.close()