linux-kernel - Re: [PATCH] tools/vm/page_owner

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Date:   Sat, 11 Sep 2021 15:25:20 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Zhenliang Wei <weizhenliang@...wei.com>
Cc:     <tangbin@...s.chinamobile.com>,
        <zhangshengju@...s.chinamobile.com>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>, <nixiaoming@...wei.com>,
        <xiaoqian9@...wei.com>
Subject: Re: [PATCH] tools/vm/page_owner_sort.c: count and sort by mem

On Fri, 10 Sep 2021 11:03:43 +0800 Zhenliang Wei <weizhenliang@...wei.com> wrote:

> When viewing page owner information, we may be more concerned about the
> total memory than the number of stack occurrences. Therefore, the
> following adjustments are made:
> 1. Added the statistics on the total number of pages.
> 2. Added the optional parameter "-m" to configure the program to sort by
>    memory (total pages).
> 

Why does it add regexp matching to add_list()?  Presumably this is some
enhancement to the user interface which I cannot see documented in the
changelog or the code comments,

Can we please add/maintain a full description of the user interface in,
I guess, Documentation/vm/page_owner.rst?

> @@ -59,12 +65,50 @@ static int compare_num(const void *p1, const void *p2)
>  	return l2->num - l1->num;
>  }
>  
> +static int compare_page_num(const void *p1, const void *p2)
> +{
> +	const struct block_list *l1 = p1, *l2 = p2;
> +
> +	return l2->page_num - l1->page_num;
> +}
> +
> +static int get_page_num(char *buf)
> +{
> +	int err, val_len, order_val;
> +	char order_str[4] = {0};
> +	char *endptr;
> +	regmatch_t pmatch[2];
> +
> +	err = regexec(&order_pattern, buf, 2, pmatch, REG_NOTBOL);
> +	if (err != 0 || pmatch[1].rm_so == -1) {
> +		printf("no order pattern in %s\n", buf);

Shouldn't error messages normally be directed to stderr?  We aren't
very consistent about this but it was the accepted thing to do 20-30
years ago, lol.

> +		return 0;
> +	}
> +	val_len = pmatch[1].rm_eo - pmatch[1].rm_so;
> +	if (val_len > 2) /* max_order should not exceed 2 digits */
> +		goto wrong_order;
> +
> +	memcpy(order_str, buf + pmatch[1].rm_so, val_len);
> +
> +	errno = 0;
> +	order_val = strtol(order_str, &endptr, 10);
> +	if (errno != 0 || endptr == order_str || *endptr != '\0')
> +		goto wrong_order;
> +
> +	return 1 << order_val;
> +
> +wrong_order:
> +	printf("wrong order in follow buf:\n%s\n", buf);
> +	return 0;
> +}
> +
>  static void add_list(char *buf, int len)
>  {
>  	if (list_size != 0 &&
>  	    len == list[list_size-1].len &&
>  	    memcmp(buf, list[list_size-1].txt, len) == 0) {
>  		list[list_size-1].num++;
> +		list[list_size-1].page_num += get_page_num(buf);
>  		return;
>  	}
>  	if (list_size == max_size) {
> @@ -74,6 +118,7 @@ static void add_list(char *buf, int len)
>  	list[list_size].txt = malloc(len+1);
>  	list[list_size].len = len;
>  	list[list_size].num = 1;
> +	list[list_size].page_num = get_page_num(buf);
>  	memcpy(list[list_size].txt, buf, len);
>  	list[list_size].txt[len] = 0;
>  	list_size++;
> @@ -85,6 +130,13 @@ static void add_list(char *buf, int len)
>  
>  #define BUF_SIZE	(128 * 1024)
>  
> +static void usage(void)
> +{
> +	printf("Usage: ./page_owner_sort [-m] <input> <output>\n"
> +		"-m	Sort by total memory. If not set this option, sort by times\n"

s/If not set this option/If this option is unset/