On 11/27/20 8:23 PM, Souptick Joarder wrote:
On Sat, Nov 28, 2020 at 12:36 AM Vlastimil Babka <vbabka@xxxxxxx> wrote:
On 11/27/20 7:57 PM, Georgi Djakov wrote:
> Hi Vlastimil,
>
> Thanks for the comment!
>
> On 11/27/20 19:52, Vlastimil Babka wrote:
>> On 11/12/20 8:14 PM, Andrew Morton wrote:
>>> On Thu, 12 Nov 2020 20:41:06 +0200 Georgi Djakov <georgi.djakov@xxxxxxxxxx>
>>> wrote:
>>>
>>>> From: Liam Mark <lmark@xxxxxxxxxxxxxx>
>>>>
>>>> Collect the time for each allocation recorded in page owner so that
>>>> allocation "surges" can be measured.
>>>>
>>>> Record the pid for each allocation recorded in page owner so that
>>>> the source of allocation "surges" can be better identified.
>>>
>>> Please provide a description of why this is considered useful. What
>>> has it been used for, what problems has it been used to solve?
>>
>> Worth noting that on x86_64 it doubles the size of struct page_owner
>> from 16 bytes to 32, so it better be justified:
>
> Well, that's true. But for debug options there is almost always some penalty.
> The timestamp and pid information is very useful for me (and others, i believe)
> when doing memory analysis. On a crash for example, we can get this information
> from kdump (or RAM-dump) and look into it to catch memory allocation problems
> more easily.
Right. Btw, you should add printing the info to __dump_page_owner().
> If you find the above argument not strong enough, how about a separate config
> option for this? Maybe something like CONFIG_PAGE_OWNER_EXTENDED, which could
> be enabled in addition to CONFIG_PAGE_OWNER?
It might be strong enough if it's mentioned in changelog, and also what exactly
the space tradeoff is :)
Just a thought ... putting it inside CONFIG_PAGE_OWNER_DEBUG might be
better if it is used
purely for debugging purposes.
I don't think we need to introduce new config just yet, until someone makes the
case for it. Even then, it could be instead doable as an extension to
"page_owner=on" boot option.
I mean let's add those fields, but improve the changelog.
You can also mention that SLUB object tracking has also pid+timestamp.
> Thanks,
> Georgi
>
>>
>> struct page_owner {
>> short unsigned int order; /* 0 2 */
>> short int last_migrate_reason; /* 2 2 */
>> gfp_t gfp_mask; /* 4 4 */
>> depot_stack_handle_t handle; /* 8 4 */
>> depot_stack_handle_t free_handle; /* 12 4 */
>> u64 ts_nsec; /* 16 8 */
>> int pid; /* 24 4 */
>>
>> /* size: 32, cachelines: 1, members: 7 */
>> /* padding: 4 */
>> /* last cacheline: 32 bytes */
>> };
>>
>
