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Date: Mon, 4 Sep 2017 11:30:55 +0300 From: Konstantin Khlebnikov <khlebnikov@...dex-team.ru> To: Kyeongdon Kim <kyeongdon.kim@....com>, akpm@...ux-foundation.org, sfr@...b.auug.org.au Cc: ying.huang@...el.com, vbabka@...e.cz, hannes@...xchg.org, xieyisheng1@...wei.com, luto@...nel.org, shli@...com, mhocko@...e.com, mgorman@...hsingularity.net, hillf.zj@...baba-inc.com, kemi.wang@...el.com, rientjes@...gle.com, bigeasy@...utronix.de, iamjoonsoo.kim@....com, bongkyu.kim@....com, linux-kernel@...r.kernel.org, linux-mm@...ck.org, netdev <netdev@...r.kernel.org> Subject: Re: [PATCH] mm/vmstats: add counters for the page frag cache On 04.09.2017 04:35, Kyeongdon Kim wrote: > Thanks for your reply, > But I couldn't find "NR_FRAGMENT_PAGES" in linux-next.git .. is that vmstat counter? or others? > I mean rather than adding bunch vmstat counters for operations it might be worth to add page counter which will show current amount of these pages. But this seems too low-level for tracking, common counters for all network buffers would be more useful but much harder to implement. As I can see page owner is able to save stacktrace where allocation happened, this makes debugging mostly trivial without any counters. If it adds too much overhead - just track random 1% of pages, should be enough for finding leak. > As you know, page_frag_alloc() directly calls __alloc_pages_nodemask() function, > so that makes too difficult to see memory usage in real time even though we have "/meminfo or /slabinfo.." information. > If there was a way already to figure out the memory leakage from page_frag_cache in mainline, I agree your opinion > but I think we don't have it now. > > If those counters too much in my patch, > I can say two values (pgfrag_alloc and pgfrag_free) are enough to guess what will happen > and would remove pgfrag_alloc_calls and pgfrag_free_calls. > > Thanks, > Kyeongdon Kim > > On 2017-09-01 오후 6:12, Konstantin Khlebnikov wrote: >> IMHO that's too much counters. >> Per-node NR_FRAGMENT_PAGES should be enough for guessing what's going on. >> Perf probes provides enough features for furhter debugging. >> >> On 01.09.2017 02:37, Kyeongdon Kim wrote: >> > There was a memory leak problem when we did stressful test >> > on Android device. >> > The root cause of this was from page_frag_cache alloc >> > and it was very hard to find out. >> > >> > We add to count the page frag allocation and free with function call. >> > The gap between pgfrag_alloc and pgfrag_free is good to to calculate >> > for the amount of page. >> > The gap between pgfrag_alloc_calls and pgfrag_free_calls is for >> > sub-indicator. >> > They can see trends of memory usage during the test. >> > Without it, it's difficult to check page frag usage so I believe we >> > should add it. >> > >> > Signed-off-by: Kyeongdon Kim <kyeongdon.kim@....com> >> > ---
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