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.
>
> 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 */
> >> };
> >>
> >
>
>
