Messages in this thread | | | From | lizhe.67@bytedanc ... | Subject | Re: [PATCH] page_ext: move up page_ext_init() to catch early page allocation if DEFERRED_STRUCT_PAGE_INIT is n | Date | Sat, 20 Aug 2022 09:02:57 +0800 |
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On 2022-08-18 7:36 UTC, mhocko@suse.com wrote: >> From: Li Zhe <lizhe.67@bytedance.com> >> >> In 'commit 2f1ee0913ce5 ("Revert "mm: use early_pfn_to_nid in page_ext_init"")', >> we call page_ext_init() after page_alloc_init_late() to avoid some panic >> problem. It seems that we cannot track early page allocations in current >> kernel even if page structure has been initialized early. >> >> This patch move up page_ext_init() to catch early page allocations when >> DEFERRED_STRUCT_PAGE_INIT is n. After this patch, we only need to turn >> DEFERRED_STRUCT_PAGE_INIT to n then we are able to analyze the early page >> allocations. This is useful especially when we find that the free memory >> value is not the same right after different kernel booting. > >is this actually useful in practice? I mean who is going to disable >DEFERRED_STRUCT_PAGE_INIT and recompile the kernel for debugging early >allocations?
Yes it is useful. We use this method to catch the difference of early page allocations between two kernel.
> I do see how debugging those early allocations might be useful but that > would require a boot time option to be practical IMHO. Would it make > sense to add a early_page_ext parameter which would essentially disable > the deferred ipage initialization. That should be quite trivial to > achieve (just hook into defer_init AFAICS).
It is a good idea. A cmdline parameter is a flexible and dynamic method for us to decide whether to defer page's and page_ext's initilization. For comparison, this patch provides a static method to decide whether to defer page's and page_ext's initilization. They are not conflicting. My next work is trying to achieve your idea. -- Li Zhe
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