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: Michael Albinus <michael.albinus <at> gmx.de>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#51699: closed (29.0.50; [PATCH] Improve performance of
 'file-name-case-insensitive-p' for Tramp files)
Date: Thu, 11 Nov 2021 18:52:02 +0000

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Your message dated Thu, 11 Nov 2021 19:51:14 +0100
with message-id <874k8iil0d.fsf <at> gmx.de>
and subject line Re: bug#51699: 29.0.50; [PATCH] Improve performance of 'file-name-case-insensitive-p' for Tramp files
has caused the debbugs.gnu.org bug report #51699,
regarding 29.0.50; [PATCH] Improve performance of 'file-name-case-insensitive-p' for Tramp files
to be marked as done.

(If you believe you have received this mail in error, please contact
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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

[Message part 3 (text/plain, inline)]

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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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.

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