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From: Sean Anderson <seanga2@gmail.com>
To: weizhenliang <weizhenliang@huawei.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>
Cc: Changhee Han <ch0.han@lge.com>,
	Tang Bin <tangbin@cmss.chinamobile.com>,
	Zhang Shengju <zhangshengju@cmss.chinamobile.com>
Subject: Re: [PATCH v2 1/2] tools/vm/page_owner_sort.c: Sort by stacktrace before culling
Date: Thu, 25 Nov 2021 11:26:59 -0500	[thread overview]
Message-ID: <bf1b7d78-9945-c3be-ff1b-53cf5d3f0878@gmail.com> (raw)
In-Reply-To: <22bad523dffb4681a201e6fedef7c50d@huawei.com>

On 11/25/21 4:46 AM, weizhenliang wrote:
> On 2021/11/25 3:37, Sean Anderson <seanga2@gmail.com> wrote:
> 
>> static int compare_num(const void *p1, const void *p2) @@ -121,6
>> +122,7 @@ static void add_list(char *buf, int len)
>> list[list_size].page_num = get_page_num(buf);
>> memcpy(list[list_size].txt, buf, len);  list[list_size].txt[len] = 0;
>> + list[list_size].stacktrace = strchr(list[list_size].txt, '\n');
> 
> When read_block gets an empty line, buf is "\n", then the stacktrace is NULL
> 
>> list_size++;
>> if (list_size % 1000 == 0) {
>> printf("loaded %d\r", list_size);
>> @@ -199,7 +201,7 @@ int main(int argc, char **argv)
>>
>> printf("sorting ....\n");
>>
>> - qsort(list, list_size, sizeof(list[0]), compare_txt);
>> + qsort(list, list_size, sizeof(list[0]), compare_stacktrace);
>>
>> list2 = malloc(sizeof(*list) * list_size);  if (!list2) { @@ -211,7
>> +213,7 @@ int main(int argc, char **argv)
>>
>> for (i = count = 0; i < list_size; i++) {  if (count == 0 ||
>> - strcmp(list2[count-1].txt, list[i].txt) != 0) {
>> + strcmp(list2[count-1].stacktrace, list[i].stacktrace) != 0) {
> 
> And when stacktrace is NULL, a segmentation fault will be triggered here.

Ah, whoops. Looks like I check for this in compare_stacktrace but not here.

>> list2[count++] = list[i];
>> } else {
>> list2[count-1].num += list[i].num;
> 
> 1. Maybe you can check whether the ret of read_block is 0 before add_list,
> or whether the len of buf is 0 in add_list

I think this is the best route.

Since this seems to have already been applied I've sent a follow-up patch.

--Sean


  reply	other threads:[~2021-11-25 16:47 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-25  9:46 weizhenliang
2021-11-25 16:26 ` Sean Anderson [this message]
  -- strict thread matches above, loose matches on Subject: below --
2021-11-24 19:37 Sean Anderson

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