[PATCH 2/4] proc: replace seq_printf on seq_putc to speed up /proc/pid/smaps

[Andrei Vagin <avagin@xxxxxxxxxx>]

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

Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Signed-off-by: Andrei Vagin <avagin@xxxxxxxxxx>
---
 fs/proc/task_mmu.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 3026feda0432..65ae54659833 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -688,8 +688,9 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
 		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');
-- 
2.13.6