linux-kernel - Re: [PATCH] seq_file: Optimize seq

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Message-ID: <935fea29-86ef-4cfb-a370-0b9616a0c279@prevas.dk>
Date: Wed, 17 Apr 2024 09:53:43 +0200
From: Rasmus Villemoes <rasmus.villemoes@...vas.dk>
To: Christophe JAILLET <christophe.jaillet@...adoo.fr>,
 Alexander Viro <viro@...iv.linux.org.uk>,
 Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>
Cc: linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
 linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] seq_file: Optimize seq_puts()

On 15/04/2024 22.47, Christophe JAILLET wrote:
> Le 04/01/2024 à 14:29, Christophe JAILLET a écrit :
>> Most of seq_puts() usages are done with a string literal. In such cases,
>> the length of the string car be computed at compile time in order to save
>> a strlen() call at run-time. seq_write() can then be used instead.
>>
>> This saves a few cycles.
>>
>> To have an estimation of how often this optimization triggers:
>>     $ git grep seq_puts.*\" | wc -l
>>     3391
>>
>> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> 
> Hi,
> 
> any feed-back on this small optimisation of seq_puts()?

While you're at it, could you change the implementation of the
out-of-line seq_puts (or __seq_puts if it gets renamed to that) to
simply be seq_write(seq, s, strlen(s)) instead of duplicating the
overflow/memcpy logic.

Rasmus