* Suggestion: vc-hooks.el: Make vc-handled-backends more conservative?
@ 2006-10-10 1:44 T. V. Raman
2006-10-10 3:23 ` Stefan Monnier
0 siblings, 1 reply; 6+ messages in thread
From: T. V. Raman @ 2006-10-10 1:44 UTC (permalink / raw)
In vc-hooks.el, vc-handled-backends
is presently declared to handle a large number of backends:
(defcustom vc-handled-backends '(RCS CVS SVN SCCS Arch MCVS)
The last two --arch and MCVS have a particularly bad performance
penalty on systems that have NFS mounts in places other than /net
or /afs --- se variable vc-ignore-dir-regexp
Unless one discovers the above variable (vc-ignore-dir-regexp is
declared as a defvar, and not as defcustom)
nfs based systems take a heavy performance hit --- since function
vc-find-root recursively ascends the directory tree in attempting
to check if files are under version control.
Suggestions:
A) Possibly make vc-handled-backends more conservative by pruning
it to have RCS CVS and SVN on it by default.
B) Make vc-ignore-dir-regexp a customizable option via
defcustom,
and add a pointer to it in the docstring for
vc-handled-backends so that users discover its purpose
In my case I chased it down by examining the source code
after observing that emacs was making excessive nfs
accesses during file load and save.
--
Best Regards,
--raman
Email: raman@users.sf.net
WWW: http://emacspeak.sf.net/raman/
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^ permalink raw reply [flat|nested] 6+ messages in thread* Re: Suggestion: vc-hooks.el: Make vc-handled-backends more conservative?
2006-10-10 1:44 Suggestion: vc-hooks.el: Make vc-handled-backends more conservative? T. V. Raman
@ 2006-10-10 3:23 ` Stefan Monnier
2006-10-11 13:28 ` T. V. Raman
0 siblings, 1 reply; 6+ messages in thread
From: Stefan Monnier @ 2006-10-10 3:23 UTC (permalink / raw)
Cc: emacs-devel
> The last two --arch and MCVS have a particularly bad performance
> penalty on systems that have NFS mounts in places other than /net
> or /afs --- se variable vc-ignore-dir-regexp
> Unless one discovers the above variable (vc-ignore-dir-regexp is
> declared as a defvar, and not as defcustom)
> nfs based systems take a heavy performance hit --- since function
> vc-find-root recursively ascends the directory tree in attempting
> to check if files are under version control.
> Suggestions:
> A) Possibly make vc-handled-backends more conservative by pruning
> it to have RCS CVS and SVN on it by default.
> B) Make vc-ignore-dir-regexp a customizable option via
> defcustom,
> and add a pointer to it in the docstring for
> vc-handled-backends so that users discover its purpose
I think B is a good idea in general. Especially since vc-ignore-dir-regexp
is useful not just for NFS mounts but for any other circumstance where the
user wants to disable VC in some part of his file-system.
I think A might be a good idea as well. MetaCVS is a rather obscure
revision control system. GNU Arch is less so, but it's not that popular
either. And there are several more still unsupported but whose support
should hopefully come at some point (Mercury, bzr, git, DaRCS, monotone,
codeville, OpenCM, you-name-it). So we most likely will not want *all*
supported systems to be "active". Maybe now is not the worst time to start
down that road.
> In my case I chased it down by examining the source code after
> observing that emacs was making excessive nfs accesses during file
> load and save.
Just to make sure that it can only be fixed with something like
vc-ignore-dir-regexp, could you describe the particular circumstance where
this happens, as well as describe as precisely as possible what
actually happens?
Stefan
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: Suggestion: vc-hooks.el: Make vc-handled-backends more conservative?
2006-10-10 3:23 ` Stefan Monnier
@ 2006-10-11 13:28 ` T. V. Raman
2006-10-11 18:28 ` Stefan Monnier
0 siblings, 1 reply; 6+ messages in thread
From: T. V. Raman @ 2006-10-11 13:28 UTC (permalink / raw)
Cc: raman, emacs-devel
Stephane --
Here is what caused me to chase down the problem.
Consider an environment where your home dir (and all users home
dirs) come from nfs and are visible as /home/user
Also assume that stat calls on nfs dirs is slow.
I found that everytime I opened a file or saved a buffer I saw
slowness. If the nfs filers were having a bad day then things in
emacs got really really bad.
I also observed by tailing /var/log/messages that the machine was
waiting on nfs responses for stat calls on /home/MCVS and
/home/{arch} --- neither of which existed --- but that still
meant you waited for the nfs system to say so.
After grepping around for {arch} and MCVS in the elisp sources I
saw that they showed up in VC -- I then toggled debug on quit
(which is what I should have done int he first place)--
saw where emacs was blocked, and the rest was easy --- since the
call in vc-find-root was the one that was initiating the stat
call on /home/MCVS and /home{arch} and since the code indicated
that the cleanest way to turn it off (clean == closest to point
of problem) was vc-ignore-dir-regexp that was the variable I
ended up setting.
Hope this helps--
>>>>> "Stefan" == Stefan Monnier <monnier@iro.umontreal.ca> writes:
>> The last two --arch and MCVS have a particularly bad
>> performance penalty on systems that have NFS mounts in
>> places other than /net or /afs --- se variable
>> vc-ignore-dir-regexp
Stefan>
>> Unless one discovers the above variable
>> (vc-ignore-dir-regexp is declared as a defvar, and not as
>> defcustom) nfs based systems take a heavy performance hit
>> --- since function vc-find-root recursively ascends the
>> directory tree in attempting to check if files are under
>> version control.
Stefan>
>> Suggestions:
Stefan>
>> A) Possibly make vc-handled-backends more conservative by
>> pruning it to have RCS CVS and SVN on it by default.
Stefan>
>> B) Make vc-ignore-dir-regexp a customizable option via
>> defcustom, and add a pointer to it in the docstring for
>> vc-handled-backends so that users discover its purpose
Stefan>
Stefan> I think B is a good idea in general. Especially
Stefan> since vc-ignore-dir-regexp is useful not just for NFS
Stefan> mounts but for any other circumstance where the user
Stefan> wants to disable VC in some part of his file-system.
Stefan>
Stefan> I think A might be a good idea as well. MetaCVS is a
Stefan> rather obscure revision control system. GNU Arch is
Stefan> less so, but it's not that popular either. And there
Stefan> are several more still unsupported but whose support
Stefan> should hopefully come at some point (Mercury, bzr,
Stefan> git, DaRCS, monotone, codeville, OpenCM,
Stefan> you-name-it). So we most likely will not want *all*
Stefan> supported systems to be "active". Maybe now is not
Stefan> the worst time to start down that road.
Stefan>
>> In my case I chased it down by examining the source code
>> after observing that emacs was making excessive nfs
>> accesses during file load and save.
Stefan>
Stefan> Just to make sure that it can only be fixed with
Stefan> something like vc-ignore-dir-regexp, could you
Stefan> describe the particular circumstance where this
Stefan> happens, as well as describe as precisely as possible
Stefan> what actually happens?
Stefan>
Stefan>
Stefan> Stefan
--
Best Regards,
--raman
Email: raman@users.sf.net
WWW: http://emacspeak.sf.net/raman/
AIM: emacspeak GTalk: tv.raman.tv@gmail.com
PGP: http://emacspeak.sf.net/raman/raman-almaden.asc
Google: tv+raman
IRC: irc://irc.freenode.net/#emacs
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: Suggestion: vc-hooks.el: Make vc-handled-backends more conservative?
2006-10-11 13:28 ` T. V. Raman
@ 2006-10-11 18:28 ` Stefan Monnier
2006-10-13 1:31 ` T. V. Raman
0 siblings, 1 reply; 6+ messages in thread
From: Stefan Monnier @ 2006-10-11 18:28 UTC (permalink / raw)
Cc: emacs-devel
> Consider an environment where your home dir (and all users home
> dirs) come from nfs and are visible as /home/user
Hmm... now that I look at the code I see that the optimization I had put for
this common case is actually missing. Can you try the patch below, see if
it helps?
Stefan
--- orig/lisp/vc-hooks.el
+++ mod/lisp/vc-hooks.el
@@ -52,11 +52,13 @@
(defvar vc-header-alist ())
(make-obsolete-variable 'vc-header-alist 'vc-BACKEND-header)
-(defvar vc-ignore-dir-regexp "\\`\\([\\/][\\/]\\|/net/\\|/afs/\\)\\'"
- "Regexp matching directory names that are not under VC's control.
+(defcustom vc-ignore-dir-regexp "\\`\\([\\/][\\/]\\|/net/\\|/afs/\\)\\'"
+ "Regexp matching directory names that are not under VC's control.
The default regexp prevents fruitless and time-consuming attempts
to determine the VC status in directories in which filenames are
-interpreted as hostnames.")
+interpreted as hostnames."
+ :type 'regexp
+ :group 'vc)
(defcustom vc-handled-backends '(RCS CVS SVN SCCS Arch MCVS)
;; Arch and MCVS come last because they are per-tree rather than per-dir.
@@ -308,6 +310,9 @@
"Find the root of a checked out project.
The function walks up the directory tree from FILE looking for WITNESS.
If WITNESS if not found, return nil, otherwise return the root."
+ ;; Represent /home/luser/foo as ~/foo so that we don't try to look for
+ ;; witnesses in /home or in /.
+ (setq file (abbreviate-file-name file))
(let ((root nil))
(while (not (or root
(equal file (setq file (file-name-directory file)))
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: Suggestion: vc-hooks.el: Make vc-handled-backends more conservative?
2006-10-11 18:28 ` Stefan Monnier
@ 2006-10-13 1:31 ` T. V. Raman
2006-10-13 5:23 ` Stefan Monnier
0 siblings, 1 reply; 6+ messages in thread
From: T. V. Raman @ 2006-10-13 1:31 UTC (permalink / raw)
Cc: raman, emacs-devel
Your patch appears to work. However it is still more efficient in
my environment to prune out arch and mcvs ---
>>>>> "Stefan" == Stefan Monnier <monnier@iro.umontreal.ca> writes:
>> Consider an environment where your home dir (and all users
>> home dirs) come from nfs and are visible as /home/user
Stefan>
Stefan> Hmm... now that I look at the code I see that the
Stefan> optimization I had put for this common case is
Stefan> actually missing. Can you try the patch below, see
Stefan> if it helps?
Stefan>
Stefan>
Stefan> Stefan
Stefan>
Stefan>
Stefan> --- orig/lisp/vc-hooks.el +++ mod/lisp/vc-hooks.el @@
Stefan> -52,11 +52,13 @@ (defvar vc-header-alist ())
Stefan> (make-obsolete-variable 'vc-header-alist
Stefan> 'vc-BACKEND-header)
Stefan>
Stefan> -(defvar vc-ignore-dir-regexp
Stefan> "\\`\\([\\/][\\/]\\|/net/\\|/afs/\\)\\'" - "Regexp
Stefan> matching directory names that are not under VC's
Stefan> control. +(defcustom vc-ignore-dir-regexp
Stefan> "\\`\\([\\/][\\/]\\|/net/\\|/afs/\\)\\'" + "Regexp
Stefan> matching directory names that are not under VC's
Stefan> control. The default regexp prevents fruitless and
Stefan> time-consuming attempts to determine the VC status in
Stefan> directories in which filenames are -interpreted as
Stefan> hostnames.") +interpreted as hostnames." + :type
Stefan> 'regexp + :group 'vc)
Stefan>
Stefan> (defcustom vc-handled-backends '(RCS CVS SVN SCCS
Stefan> Arch MCVS) ;; Arch and MCVS come last because they
Stefan> are per-tree rather than per-dir. @@ -308,6 +310,9
Stefan> @@ "Find the root of a checked out project. The
Stefan> function walks up the directory tree from FILE
Stefan> looking for WITNESS. If WITNESS if not found, return
Stefan> nil, otherwise return the root." + ;; Represent
Stefan> /home/luser/foo as ~/foo so that we don't try to look
Stefan> for + ;; witnesses in /home or in /. + (setq file
Stefan> (abbreviate-file-name file)) (let ((root nil)) (while
Stefan> (not (or root (equal file (setq file
Stefan> (file-name-directory file)))
Stefan>
Stefan>
Stefan> _______________________________________________
Stefan> Emacs-devel mailing list Emacs-devel@gnu.org
Stefan> http://lists.gnu.org/mailman/listinfo/emacs-devel
--
Best Regards,
--raman
Email: raman@users.sf.net
WWW: http://emacspeak.sf.net/raman/
AIM: emacspeak GTalk: tv.raman.tv@gmail.com
PGP: http://emacspeak.sf.net/raman/raman-almaden.asc
Google: tv+raman
IRC: irc://irc.freenode.net/#emacs
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2006-10-13 5:23 UTC | newest]
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2006-10-10 1:44 Suggestion: vc-hooks.el: Make vc-handled-backends more conservative? T. V. Raman
2006-10-10 3:23 ` Stefan Monnier
2006-10-11 13:28 ` T. V. Raman
2006-10-11 18:28 ` Stefan Monnier
2006-10-13 1:31 ` T. V. Raman
2006-10-13 5:23 ` Stefan Monnier
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