Commit 5c5ab971 authored by Alexey Dobriyan's avatar Alexey Dobriyan Committed by Linus Torvalds
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proc: speed up /proc/*/statm 



top(1) reads all /proc/*/statm files but kernel threads will always have
zeros.  Print those zeroes directly without going through
seq_put_decimal_ull().

Speed up reading /proc/2/statm (which is kthreadd) is like 3%.

My system has more kernel threads than normal processes after booting KDE.

Signed-off-by: default avatarAlexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20200307154435.GA2788@avx2


Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent d919b33d

fs/proc/array.c

+23 −16
Original line number Diff line number Diff line
@@ -635,13 +635,18 @@ int proc_tgid_stat(struct seq_file *m, struct pid_namespace *ns, 
int proc_pid_statm(struct seq_file *m, struct pid_namespace *ns,

			struct pid *pid, struct task_struct *task)

{

	unsigned long size = 0, resident = 0, shared = 0, text = 0, data = 0;

	struct mm_struct *mm = get_task_mm(task);



	if (mm) {

		unsigned long size;

		unsigned long resident = 0;

		unsigned long shared = 0;

		unsigned long text = 0;

		unsigned long data = 0;



		size = task_statm(mm, &shared, &text, &data, &resident);

		mmput(mm);

	}



		/*

		 * For quick read, open code by putting numbers directly

		 * expected format is
@@ -656,7 +661,9 @@ int proc_pid_statm(struct seq_file *m, struct pid_namespace *ns, 
		seq_put_decimal_ull(m, " ", data);

		seq_put_decimal_ull(m, " ", 0);

		seq_putc(m, '\n');



	} else {

		seq_write(m, "0 0 0 0 0 0 0\n", 14);

	}

	return 0;

}