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: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx> --- Changes in v2: - Use a function, instead of a macro [Al Viro] - Handle the case of 1 char only strings, in order to use seq_putc() [Al Viro] - Use __always_inline [David Laight] V1: https://lore.kernel.org/all/5c4f7ad7b88f5026940efa9c8be36a58755ec1b3.1704374916.git.christophe.jaillet@xxxxxxxxxx/ Checked by comparing the output of a few .s files. Here is one of these outputs: $ diff -u drivers/clk/clk.s.old drivers/clk/clk.s | grep -C6 seq_w .L2918: @@ -46072,10 +46073,11 @@ call clk_prepare_unlock # # drivers/clk/clk.c:3438: clk_pm_runtime_put_all(); call clk_pm_runtime_put_all # -# drivers/clk/clk.c:3440: seq_puts(s, "}\n"); +# ./include/linux/seq_file.h:130: seq_write(m, s, __builtin_strlen(s)); + movl $2, %edx #, movq $.LC94, %rsi #, movq %rbp, %rdi # s, - call seq_puts # + call seq_write # # drivers/clk/clk.c:3441: return 0; jmp .L2917 # .size clk_dump_show, .-clk_dump_show @@ -46200,7 +46202,7 @@ leaq 128(%rbx), %r15 #, _97 movq %r15, %rdi # _97, -- # drivers/clk/clk.c:1987: __clk_recalc_rates(core, false, 0); @@ -46480,15 +46482,17 @@ call seq_printf # jmp .L2950 # .L2946: -# drivers/clk/clk.c:3315: seq_puts(s, "-----"); +# ./include/linux/seq_file.h:130: seq_write(m, s, __builtin_strlen(s)); call __sanitizer_cov_trace_pc # + movl $5, %edx #, movq $.LC100, %rsi #, movq %rbp, %rdi # s, - call seq_puts # + call seq_write # +# ./include/linux/seq_file.h:131: } jmp .L2947 # .L2957: # drivers/clk/clk.c:1903: return clk_core_get_accuracy_no_lock(core); - xorl %r14d, %r14d # _34 + xorl %r14d, %r14d # _35 -- @@ -46736,21 +46740,22 @@ call __sanitizer_cov_trace_pc # leaq 240(%r12), %rdi #, tmp101 call __tsan_read8 # -# drivers/clk/clk.c:3355: seq_puts(s, " enable prepare protect duty hardware connection\n"); - movq $.LC104, %rsi #, +# ./include/linux/seq_file.h:130: seq_write(m, s, __builtin_strlen(s)); + movl $142, %edx #, movq %r12, %rdi # s, + movq $.LC104, %rsi #, # drivers/clk/clk.c:3352: struct hlist_head **lists = s->private; movq 240(%r12), %r13 # s_10(D)->private, lists -# drivers/clk/clk.c:3355: seq_puts(s, " enable prepare protect duty hardware connection\n"); - call seq_puts # -# drivers/clk/clk.c:3356: seq_puts(s, " clock count count count rate accuracy phase cycle enable consumer id\n"); +# ./include/linux/seq_file.h:130: seq_write(m, s, __builtin_strlen(s)); + call seq_write # + movl $142, %edx #, movq $.LC105, %rsi #, movq %r12, %rdi # s, - call seq_puts # -# drivers/clk/clk.c:3357: seq_puts(s, "---------------------------------------------------------------------------------------------------------------------------------------------\n"); + call seq_write # movq $.LC106, %rsi #, movq %r12, %rdi # s, - call seq_puts # + movl $142, %edx #, + call seq_write # # drivers/clk/clk.c:3359: ret = clk_pm_runtime_get_all(); call clk_pm_runtime_get_all # # drivers/clk/clk.c:3360: if (ret) @@ -57943,7 +57948,7 @@ subq $88, %rsp #, # drivers/clk/clk.c:5338: { The output for seq_putc() generation has also be checked and works. --- fs/seq_file.c | 4 ++-- include/linux/seq_file.h | 13 ++++++++++++- 2 files changed, 14 insertions(+), 3 deletions(-) diff --git a/fs/seq_file.c b/fs/seq_file.c index f5fdaf3b1572..8ef0a07033ca 100644 --- a/fs/seq_file.c +++ b/fs/seq_file.c @@ -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 diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h index 234bcdb1fba4..8bd4fda6e027 100644 --- a/include/linux/seq_file.h +++ b/include/linux/seq_file.h @@ -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, -- 2.44.0
