On 30.08.22 04:41, Zhaoyang Huang wrote: > On Mon, Aug 29, 2022 at 8:19 PM David Hildenbrand <david@xxxxxxxxxx> wrote: >> >> On 26.08.22 05:23, Zhaoyang Huang wrote: >>> On Fri, Aug 26, 2022 at 11:13 AM zhaoyang.huang >>> <zhaoyang.huang@xxxxxxxxxx> wrote: >>>> >>>> From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx> >>>> >>>> It is no need to scan reserved page, skip it. >>>> >>>> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx> >>>> --- >>>> mm/kmemleak.c | 2 +- >>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>> >>>> diff --git a/mm/kmemleak.c b/mm/kmemleak.c >>>> index a182f5d..c546250 100644 >>>> --- a/mm/kmemleak.c >>>> +++ b/mm/kmemleak.c >>>> @@ -1471,7 +1471,7 @@ static void kmemleak_scan(void) >>>> if (page_zone(page) != zone) >>>> continue; >>>> /* only scan if page is in use */ >>>> - if (page_count(page) == 0) >>>> + if (page_count(page) == 0 || PageReserved(page)) >>> Sorry for previous stupid code by my faint, correct it here >> >> Did you even test the initial patch? >> >> I wonder why we should consider this change >> >> (a) I doubt it's a performance issue. If it is, please provide numbers >> before/after. > For Android-like SOC systems where AP(cpu runs linux) are one of the > memory consumers which are composed of other processors such as modem, > isp,wcn etc. The reserved memory occupies a certain number of > memory(could be 30% of MemTotal) which makes scan reserved pages > pointless. But we only scan the memmap (struct page) here and not the actual memory. Do you have any performance numbers showing that there is even an observable change? >> (b) We'll stop scanning early allocations. As the memmap is usually >> allocated early during boot ... we'll stop scanning essentially the >> whole mmap and that whole loop would be dead code? What am i >> missing? > memmap refers to pages here? If we can surpass these as it exist > permanently during life period. Besides, I wonder if PageLRU should > also be skipped? > - if (page_count(page) == 0) > + if (page_count(page) == 0 || > PageReserved(page) || PageLRU(page)) I think we need a really good justification to start poking holes into the memmap scanner. I'm no expert on this code (and under which circumstances we actually might find referenced objects in a memmap), though. But we should be careful with that. -- Thanks, David / dhildenb
