linux-kernel - Re: [PATCH] tools/vm/page_owner_sort.c: add switch between culling by stacktrace and txt

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Date:   Mon, 29 Nov 2021 21:23:41 -0500
From:   Sean Anderson <seanga2@...il.com>
To:     Yinan Zhang <zhangyinan2019@...il.szu.edu.cn>,
        akpm@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tools/vm/page_owner_sort.c: add switch between culling by
 stacktrace and txt

On 11/29/21 9:56 AM, Yinan Zhang wrote:
> Culling by comparing stacktrace would casue loss of some
> information. For example, if there exists 2 blocks which
> have the same stacktrace and the different head info
> 
> Page allocated via order 0, mask 0x108c48(...), pid 73696,
>   ts 1578829190639010 ns, free_ts 1576583851324450 ns
>   prep_new_page+0x80/0xb8
>   get_page_from_freelist+0x924/0xee8
>   __alloc_pages+0x138/0xc18
>   alloc_pages+0x80/0xf0
>   __page_cache_alloc+0x90/0xc8
> 
> Page allocated via order 0, mask 0x108c48(...), pid 61806,
>   ts 1354113726046100 ns, free_ts 1354104926841400 ns
>   prep_new_page+0x80/0xb8
>   get_page_from_freelist+0x924/0xee8
>   __alloc_pages+0x138/0xc18
>   alloc_pages+0x80/0xf0
>   __page_cache_alloc+0x90/0xc8
> 
> After culling, it would be like this
> 
> 2 times, 2 pages:
> Page allocated via order 0, mask 0x108c48(...), pid 73696,
>   ts 1578829190639010 ns, free_ts 1576583851324450 ns
>   prep_new_page+0x80/0xb8
>   get_page_from_freelist+0x924/0xee8
>   __alloc_pages+0x138/0xc18
>   alloc_pages+0x80/0xf0
>   __page_cache_alloc+0x90/0xc8
> 

This is working as designed. IMO there's no point in separating
allocations like this which differ only in PID and timestamp, since you
will get no grouping at all.

> The info of second block missed. So, add -c to turn on culling
> by stacktrace. By default, it will cull by txt.

Please keep the default to actually do something in the cull step.

> Signed-off-by: Yinan Zhang <zhangyinan2019@...il.szu.edu.cn>
> ---
>   tools/vm/page_owner_sort.c | 23 ++++++++++++++++++++---
>   1 file changed, 20 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/vm/page_owner_sort.c b/tools/vm/page_owner_sort.c
> index 1b2acf02d3cd..492be7f752c0 100644
> --- a/tools/vm/page_owner_sort.c
> +++ b/tools/vm/page_owner_sort.c
> @@ -51,6 +51,13 @@ int read_block(char *buf, int buf_size, FILE *fin)
>   	return -1; /* EOF or no space left in buf. */
>   }
>   
> +static int compare_txt(const void *p1, const void *p2)
> +{
> +	const struct block_list *l1 = p1, *l2 = p2;
> +
> +	return strcmp(l1->txt, l2->txt);
> +}
> +
>   static int compare_stacktrace(const void *p1, const void *p2)
>   {
>   	const struct block_list *l1 = p1, *l2 = p2;
> @@ -137,12 +144,14 @@ static void usage(void)
>   		"-m	Sort by total memory.\n"
>   		"-s	Sort by the stack trace.\n"
>   		"-t	Sort by times (default).\n"
> +		"-c	cull by comparing stacktrace instead of total block.\n"
>   	);
>   }
>   
>   int main(int argc, char **argv)
>   {
>   	int (*cmp)(const void *, const void *) = compare_num;
> +	int cull_st = 0;
>   	FILE *fin, *fout;
>   	char *buf;
>   	int ret, i, count;
> @@ -151,7 +160,7 @@ int main(int argc, char **argv)
>   	int err;
>   	int opt;
>   
> -	while ((opt = getopt(argc, argv, "mst")) != -1)
> +	while ((opt = getopt(argc, argv, "mstc")) != -1)
>   		switch (opt) {
>   		case 'm':
>   			cmp = compare_page_num;
> @@ -162,6 +171,9 @@ int main(int argc, char **argv)
>   		case 't':
>   			cmp = compare_num;
>   			break;
> +		case 'c':
> +			cull_st = 1;
> +			break;

Can we set a "cull_cmp" variable like cmp?

Looking forward, I think something like

	page_owner_sort --cull=stacktrace --sort=times foo bar

would be nice.

--Sean

>   		default:
>   			usage();
>   			exit(1);
> @@ -209,7 +221,10 @@ int main(int argc, char **argv)
>   
>   	printf("sorting ....\n");
>   
> -	qsort(list, list_size, sizeof(list[0]), compare_stacktrace);
> +	if (cull_st == 1)
> +		qsort(list, list_size, sizeof(list[0]), compare_stacktrace);
> +	else
> +		qsort(list, list_size, sizeof(list[0]), compare_txt);
>   
>   	list2 = malloc(sizeof(*list) * list_size);
>   	if (!list2) {
> @@ -219,9 +234,11 @@ int main(int argc, char **argv)
>   
>   	printf("culling\n");
>   
> +	long offset = cull_st ? &list[0].stacktrace - &list[0].txt : 0;
> +
>   	for (i = count = 0; i < list_size; i++) {
>   		if (count == 0 ||
> -		    strcmp(list2[count-1].stacktrace, list[i].stacktrace) != 0) {
> +		    strcmp(*(&list2[count-1].txt+offset), *(&list[i].txt+offset)) != 0) {
>   			list2[count++] = list[i];
>   		} else {
>   			list2[count-1].num += list[i].num;
>