84b9749a3a
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@163.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
38 lines
840 B
C
38 lines
840 B
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/init.h>
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#include <linux/kernel_stat.h>
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#include <linux/proc_fs.h>
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#include <linux/seq_file.h>
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#include "internal.h"
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/*
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* /proc/softirqs ... display the number of softirqs
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*/
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static int show_softirqs(struct seq_file *p, void *v)
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{
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int i, j;
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seq_puts(p, " ");
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for_each_possible_cpu(i)
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seq_printf(p, "CPU%-8d", i);
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seq_putc(p, '\n');
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for (i = 0; i < NR_SOFTIRQS; i++) {
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seq_printf(p, "%12s:", softirq_to_name[i]);
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for_each_possible_cpu(j)
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seq_put_decimal_ull_width(p, " ", kstat_softirqs_cpu(i, j), 10);
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seq_putc(p, '\n');
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}
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return 0;
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}
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static int __init proc_softirqs_init(void)
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{
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struct proc_dir_entry *pde;
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pde = proc_create_single("softirqs", 0, NULL, show_softirqs);
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pde_make_permanent(pde);
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return 0;
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}
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fs_initcall(proc_softirqs_init);
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