GNU bug report logs - #51699
29.0.50; [PATCH] Improve performance of 'file-name-case-insensitive-p' for Tramp files

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Jim Porter <jporterbugs <at> gmail.com>
Subject: bug#51699: closed (Re: bug#51699: 29.0.50; [PATCH] Improve
 performance of 'file-name-case-insensitive-p' for Tramp files)
Date: Thu, 11 Nov 2021 18:52:02 +0000

[Message part 1 (text/plain, inline)]

Your bug report

#51699: 29.0.50; [PATCH] Improve performance of 'file-name-case-insensitive-p' for Tramp files

which was filed against the emacs package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 51699 <at> debbugs.gnu.org.

-- 
51699: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=51699
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Michael Albinus <michael.albinus <at> gmx.de>
To: Jim Porter <jporterbugs <at> gmail.com>
Cc: 51699-done <at> debbugs.gnu.org
Subject: Re: bug#51699: 29.0.50; [PATCH] Improve performance of
 'file-name-case-insensitive-p' for Tramp files
Date: Thu, 11 Nov 2021 19:51:14 +0100

Version: 29.1

Jim Porter <jporterbugs <at> gmail.com> writes:

Hi Jim,

> From 2aec8e21a3e37728a990c4f116f60c8b12bb2110 Mon Sep 17 00:00:00 2001
> From: Jim Porter <jporterbugs <at> gmail.com>
> Date: Wed, 10 Nov 2021 16:41:00 -0800
> Subject: [PATCH] Improve performance of 'tramp-find-foreign-file-name-handler'

Thanks for this final patch. I've applied it to master. It makes
tramp-tests.el faster for most of the test cases, not only for
file-name-case-insensitive-p tests. :-)

Closing this bug.

Best regards, Michael.

[Message part 3 (message/rfc822, inline)]

From: Jim Porter <jporterbugs <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 29.0.50; [PATCH] Improve performance of
 'file-name-case-insensitive-p' for Tramp files
Date: Mon, 8 Nov 2021 19:46:05 -0800

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This is a spinoff of bug#51622. While looking at the performance of 
'abbreviate-file-name' for Tramp files, I noticed that 
'file-name-case-insensitive-p' was taking up a significant percentage of 
the execution time. I dug into this and found two main hot spots:

1) 'tramp-handle-file-name-case-insensitive-p' calling 'file-remote-p' 
and 'expand-file-name'

Since 'file-remote-p' only needed to check whether a connection was 
already established, it could be replaced with this (thanks to Michael 
Albinus for the pointer):

  (let ((non-essential t)) (tramp-connectable-p v))

'expand-file-name' also had room for a small optimization, since it 
previously called 'tramp-connectable-p' (which dissects the file if it's 
not already) and then 'with-parsed-tramp-file-name' (which dissects it 
again). I reversed the order so now there's one fewer dissection, and 
it's a bit faster.

2) Potential handlers in 'tramp-find-foreign-file-name-handler' each 
dissect the file name

Most Tramp methods have a 'tramp-FOO-file-name-p', and most of *those* 
take a file name string and dissect it. This is a lot of duplicated 
effort, so I modified 'tramp-find-foreign-file-name-handler' to pass the 
dissected file name to any of the functions that support it (this is 
indicated by an 'accepts-vec' property on the function). This probably 
warrants some documentation (at least a NEWS entry), but I wanted to be 
sure the strategy made sense before I wrote any docs.

With these changes combined, I see the following results (testing with 
the sshx method connecting to localhost on a GNU/Linux system):

* 'file-name-case-insensitive-p':
  3.5x faster, now 583μs per call
* 'tramp-handle-file-name-case-insensitive-p':
  4.5x faster, now 281μs per call
* 'tramp-find-foreign-file-name-handler':
  5.2x faster, now 45μs per call

In addition to the patches, I've attached the benchmark script that 
generated these results as well as the raw data.

[0001-Improve-performance-when-checking-case-sensitivity-o.patch (text/plain, attachment)]

[0002-Improve-performance-of-tramp-find-foreign-file-name-.patch (text/plain, attachment)]

[benchmark.el (text/plain, attachment)]

[benchmark-results.txt (text/plain, attachment)]

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