Unverified Commit 45751097 authored by Christophe JAILLET's avatar Christophe JAILLET Committed by Christian Brauner
Browse files

seq_file: Optimize seq_puts() 



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_putc() or 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
   3436

   $ git grep seq_puts.*\".\" | wc -l
   84

Signed-off-by: default avatarChristophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/a8589bffe4830dafcb9111e22acf06603fea7132.1713781332.git.christophe.jaillet@wanadoo.fr


Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
The output for seq_putc() generation has also be checked and works.
parent 0a960ba4

fs/seq_file.c

+2 −2
Original line number Diff line number Diff line
@@ -669,7 +669,7 @@ void seq_putc(struct seq_file *m, char c) 
}

EXPORT_SYMBOL(seq_putc);



void seq_puts(struct seq_file *m, const char *s)

void __seq_puts(struct seq_file *m, const char *s)

{

	int len = strlen(s);
@@ -680,7 +680,7 @@ void seq_puts(struct seq_file *m, const char *s) 
	memcpy(m->buf + m->count, s, len);

	m->count += len;

}

EXPORT_SYMBOL(seq_puts);

EXPORT_SYMBOL(__seq_puts);



/**

 * seq_put_decimal_ull_width - A helper routine for putting decimal numbers

include/linux/seq_file.h

+12 −1
Original line number Diff line number Diff line
@@ -118,7 +118,18 @@ void seq_vprintf(struct seq_file *m, const char *fmt, va_list args); 
__printf(2, 3)

void seq_printf(struct seq_file *m, const char *fmt, ...);

void seq_putc(struct seq_file *m, char c);

void seq_puts(struct seq_file *m, const char *s);

void __seq_puts(struct seq_file *m, const char *s);



static __always_inline void seq_puts(struct seq_file *m, const char *s)

{

	if (!__builtin_constant_p(*s))

		__seq_puts(m, s);

	else if (s[0] && !s[1])

		seq_putc(m, s[0]);

	else

		seq_write(m, s, __builtin_strlen(s));

}



void seq_put_decimal_ull_width(struct seq_file *m, const char *delimiter,

			       unsigned long long num, unsigned int width);

void seq_put_decimal_ull(struct seq_file *m, const char *delimiter,