linux-kernel - [PATCH AUTOSEL 5.15 8/8] proc/softirqs: replace seq_printf with seq_put_decimal_ull

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Message-ID: <20241112103745.1653994-8-sashal@kernel.org>
Date: Tue, 12 Nov 2024 05:37:42 -0500
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: David Wang <00107082@....com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Sasha Levin <sashal@...nel.org>,
	linux-fsdevel@...r.kernel.org
Subject: [PATCH AUTOSEL 5.15 8/8] proc/softirqs: replace seq_printf with seq_put_decimal_ull_width

From: David Wang <00107082@....com>

[ Upstream commit 84b9749a3a704dcc824a88aa8267247c801d51e4 ]

seq_printf is costy, on a system with n CPUs, reading /proc/softirqs
would yield 10*n decimal values, and the extra cost parsing format string
grows linearly with number of cpus. Replace seq_printf with
seq_put_decimal_ull_width have significant performance improvement.
On an 8CPUs system, reading /proc/softirqs show ~40% performance
gain with this patch.

Signed-off-by: David Wang <00107082@....com>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/proc/softirqs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/proc/softirqs.c b/fs/proc/softirqs.c
index 12901dcf57e2b..d8f4e7d54d002 100644
--- a/fs/proc/softirqs.c
+++ b/fs/proc/softirqs.c
@@ -19,7 +19,7 @@ static int show_softirqs(struct seq_file *p, void *v)
 	for (i = 0; i < NR_SOFTIRQS; i++) {
 		seq_printf(p, "%12s:", softirq_to_name[i]);
 		for_each_possible_cpu(j)
-			seq_printf(p, " %10u", kstat_softirqs_cpu(i, j));
+			seq_put_decimal_ull_width(p, " ", kstat_softirqs_cpu(i, j), 10);
 		seq_putc(p, '\n');
 	}
 	return 0;
-- 
2.43.0