Messages in this thread | | | Subject | Re: [PATCH] mm/page_owner: Record timestamp and pid | From | Vlastimil Babka <> | Date | Mon, 30 Nov 2020 13:04:05 +0100 |
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On 11/27/20 8:23 PM, Souptick Joarder wrote: > On Sat, Nov 28, 2020 at 12:36 AM Vlastimil Babka <vbabka@suse.cz> 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@linaro.org> >> >>> wrote: >> >>> >> >>>> From: Liam Mark <lmark@codeaurora.org> >> >>>> >> >>>> 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 */ >> >> }; >> >> >> > >> >> >
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