From: Andrei Vagin <avagin@xxxxxxxxxx>
Subject: proc: replace seq_printf on seq_putc to speed up /proc/pid/smaps
seq_putc() works much faster than seq_printf()
$ time python test_smaps.py
== Before patch ==
real 0m3.828s
user 0m0.413s
sys 0m3.408s
== After patch ==
real 0m3.405s
user 0m0.401s
sys 0m3.003s
== Before patch ==
- 75.51% 4.62% python [kernel.kallsyms] [k] show_smap.isra.33
- 70.88% show_smap.isra.33
+ 24.82% seq_put_decimal_ull_aligned
+ 19.78% __walk_page_range
+ 12.74% seq_printf
+ 11.08% show_map_vma.isra.23
+ 1.68% seq_puts
== After patch ==
- 69.16% 5.70% python [kernel.kallsyms] [k] show_smap.isra.33
- 63.46% show_smap.isra.33
+ 25.98% seq_put_decimal_ull_aligned
+ 20.90% __walk_page_range
+ 12.60% show_map_vma.isra.23
1.56% seq_putc
+ 1.55% seq_puts
Link: http://lkml.kernel.org/r/20180212074931.7227-2-avagin@xxxxxxxxxx
Signed-off-by: Andrei Vagin <avagin@xxxxxxxxxx>
Reviewed-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/task_mmu.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff -puN fs/proc/task_mmu.c~proc-replace-seq_printf-on-seq_putc-to-speed-up-proc-pid-smaps fs/proc/task_mmu.c
--- a/fs/proc/task_mmu.c~proc-replace-seq_printf-on-seq_putc-to-speed-up-proc-pid-smaps
+++ a/fs/proc/task_mmu.c
@@ -688,8 +688,9 @@ static void show_smap_vma_flags(struct s
if (!mnemonics[i][0])
continue;
if (vma->vm_flags & (1UL << i)) {
- seq_printf(m, "%c%c ",
- mnemonics[i][0], mnemonics[i][1]);
+ seq_putc(m, mnemonics[i][0]);
+ seq_putc(m, mnemonics[i][1]);
+ seq_putc(m, ' ');
}
}
seq_putc(m, '\n');
_
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