linux-kernel - Re: [PATCH] proc, smaps: reduce printing overhead

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Date:	Thu, 18 Aug 2016 06:26:05 -0700
From:	Joe Perches <joe@...ches.com>
To:	Michal Hocko <mhocko@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>,
	Jann Horn <jann@...jh.net>, Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH] proc, smaps: reduce printing overhead

On Thu, 2016-08-18 at 13:31 +0200, Michal Hocko wrote:

[]

> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
[]
> @@ -721,6 +721,13 @@ void __weak arch_show_smap(struct seq_file *m, struct vm_area_struct *vma)
>  {
>  }
>  
> +static void print_name_value_kb(struct seq_file *m, const char *name, unsigned long val)
> +{
> +	seq_puts(m, name);
> +	seq_put_decimal_ull(m, 0, val);
> +	seq_puts(m, " kB\n");
> +}

The seq_put_decimal_ull function has different arguments
in -next, the separator is changed to const char *.

$ git log --stat -p -1 49f87a2773000ced0c850639975f43134de48342 -- fs/seq_file.c

Maybe this change in fs/proc/meminfo.c should be
made into a public function.

$ git log --stat -p -1  5e27340c20516104c38668e597b3200f339fc64d

static void show_val_kb(struct seq_file *m, const char *s, unsigned long num)
+{
+       char v[32];
+       static const char blanks[7] = {' ', ' ', ' ', ' ',' ', ' ', ' '};
+       int len;
+
+       len = num_to_str(v, sizeof(v), num << (PAGE_SHIFT - 10));
+
+       seq_write(m, s, 16);
+
+       if (len > 0) {
+               if (len < 8)
+                       seq_write(m, blanks, 8 - len);
+
+               seq_write(m, v, len);
+       }
+       seq_write(m, " kB\n", 4);
+}