linux-kernel - [PATCH 13/13] proc: convert /proc/*/task/*/children to _print

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Message-Id: <20180827231503.26899-13-adobriyan@gmail.com>
Date:   Tue, 28 Aug 2018 02:15:03 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     akpm@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org, Alexey Dobriyan <adobriyan@...il.com>
Subject: [PATCH 13/13] proc: convert /proc/*/task/*/children to _print_integer()

Benchmark pread /proc/1/task/1/children 2^21 times on the same system:

	6.766400479 s
	4.328648442

	-36%

(need to remeasure on a controlled set of children)

Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
---
 fs/proc/array.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/proc/array.c b/fs/proc/array.c
index d0565527166a..045ce2cac1dd 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -710,9 +710,11 @@ get_children_pid(struct inode *inode, struct pid *pid_prev, loff_t pos)
 static int children_seq_show(struct seq_file *seq, void *v)
 {
 	struct inode *inode = file_inode(seq->file);
+	char buf[10 + 1], *p = buf + sizeof(buf);
 
-	seq_printf(seq, "%d ", pid_nr_ns(v, proc_pid_ns(inode)));
-	return 0;
+	*--p = ' ';
+	p = _print_integer_u32(p, pid_nr_ns(v, proc_pid_ns(inode)));
+	return seq_write(seq, p, buf + sizeof(buf) - p);
 }
 
 static void *children_seq_start(struct seq_file *seq, loff_t *pos)
-- 
2.16.4