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diff mercurial/merge.py @ 34885:df2ff314e36f

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fsmonitor: warn when fsmonitor could be used fsmonitor can significantly speed up operations on large working directories. But fsmonitor isn't enabled by default, so naive users may not realize there is a potential to make Mercurial faster. This commit introduces a warning to working directory updates when fsmonitor could be used. The following conditions must be met: * Working directory is previously empty * New working directory adds >= N files (currently 50,000) * Running on Linux or MacOS * fsmonitor not enabled * Warning not disabled via config override Because of the empty working directory restriction, most users will only see this warning during `hg clone` (assuming very few users actually do an `hg up null`). The addition of a warning may be considered a BC change. However, clone has printed warnings before. Until recently, Mercurial printed a warning with the server's certificate fingerprint when it wasn't explicitly trusted for example. The warning goes to stderr. So it shouldn't interfere with scripts parsing meaningful output. The OS restriction was on the advice of Facebook engineers, who only feel confident with watchman's stability on the supported platforms. .. feature:: Print warning when fsmonitor isn't being used on a large repository Differential Revision: https://phab.mercurial-scm.org/D894
author Gregory Szorc <gregory.szorc@gmail.com>
date Wed, 18 Oct 2017 22:57:15 +0200
parents 754b5117622f
children 1856de4d1297
line wrap: on
line diff
--- a/mercurial/merge.py	Fri Oct 06 06:48:43 2017 -0700
+++ b/mercurial/merge.py	Wed Oct 18 22:57:15 2017 +0200
@@ -25,6 +25,7 @@
 from . import (
     copies,
     error,
+    extensions,
     filemerge,
     match as matchmod,
     obsutil,
@@ -1943,6 +1944,38 @@
             # note that we're in the middle of an update
             repo.vfs.write('updatestate', p2.hex())
 
+        # Advertise fsmonitor when its presence could be useful.
+        #
+        # We only advertise when performing an update from an empty working
+        # directory. This typically only occurs during initial clone.
+        #
+        # We give users a mechanism to disable the warning in case it is
+        # annoying.
+        #
+        # We only allow on Linux and MacOS because that's where fsmonitor is
+        # considered stable.
+        fsmonitorwarning = repo.ui.configbool('fsmonitor', 'warn_when_unused')
+        fsmonitorthreshold = repo.ui.configint('fsmonitor',
+                                               'warn_update_file_count')
+        try:
+            extensions.find('fsmonitor')
+            fsmonitorenabled = repo.ui.config('fsmonitor', 'mode') != 'off'
+            # We intentionally don't look at whether fsmonitor has disabled
+            # itself because a) fsmonitor may have already printed a warning
+            # b) we only care about the config state here.
+        except KeyError:
+            fsmonitorenabled = False
+
+        if (fsmonitorwarning
+                and not fsmonitorenabled
+                and p1.node() == nullid
+                and len(actions['g']) >= fsmonitorthreshold
+                and pycompat.sysplatform.startswith(('linux', 'darwin'))):
+            repo.ui.warn(
+                _('(warning: large working directory being used without '
+                  'fsmonitor enabled; enable fsmonitor to improve performance; '
+                  'see "hg help -e fsmonitor")\n'))
+
         stats = applyupdates(repo, actions, wc, p2, overwrite, labels=labels)
         wc.flushall()