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[35.185.212.55]) by smtp.gmail.com with ESMTPSA id r10-20020aa79eca000000b0052ac1af926fsm5691446pfq.20.2022.07.12.09.21.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 12 Jul 2022 09:21:22 -0700 (PDT) Date: Tue, 12 Jul 2022 09:21:19 -0700 From: Zach O'Keefe To: Yang Shi Cc: Alex Shi , David Hildenbrand , David Rientjes , Matthew Wilcox , Michal Hocko , Pasha Tatashin , Peter Xu , Rongwei Wang , SeongJae Park , Song Liu , Vlastimil Babka , Zi Yan , Linux MM , Andrea Arcangeli , Andrew Morton , Arnd Bergmann , Axel Rasmussen , Chris Kennelly , Chris Zankel , Helge Deller , Hugh Dickins , Ivan Kokshaysky , "James E.J. Bottomley" , Jens Axboe , "Kirill A. Shutemov" , Matt Turner , Max Filippov , Miaohe Lin , Minchan Kim , Patrick Xia , Pavel Begunkov , Thomas Bogendoerfer Subject: Re: [mm-unstable v7 11/18] mm/madvise: add huge_memory:mm_madvise_collapse tracepoint Message-ID: References: <20220706235936.2197195-1-zokeefe@google.com> <20220706235936.2197195-12-zokeefe@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: ARC-Authentication-Results: i=1; imf18.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=BBp1fgIv; spf=pass (imf18.hostedemail.com: domain of zokeefe@google.com designates 209.85.216.52 as permitted sender) smtp.mailfrom=zokeefe@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1657642884; a=rsa-sha256; cv=none; b=uP73Go6hVALBkVcDhF+o9D2LkijaaDY9uGMPSqAUIviLndHEnU/cX/Kpm5Hdbnj8sFb7Wz guy5waadCzIY435DRBROduSw6VCtK3V6CWioHaJrUBc9XCS59YNDkcJlbfAPuoUsLLvuUr DD29gjs2WUpmkHk7TBBa6Ps6gBj0b1g= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1657642884; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=BI2Hqo71ItdgVswSgDxm3wxG4HB8URpKTjAGPG/df18=; b=HEgJeeEY4JnC9pd9TcJCX97Kt9kXrsWJ4+4iOC4mZVQb1QJd+ik10my8tNxb7pktipsMJ1 DMXVKr/5Nm1ejYxpgjqNCq3i7PqTCB/waiYm4RSCfmiZdQITnBcphPNA97tdjYzwn+TDmu kQXd0PAiRK6UrwqIKwSL2EgztAUDeLc= X-Rspamd-Queue-Id: F35601C00A0 Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=BBp1fgIv; spf=pass (imf18.hostedemail.com: domain of zokeefe@google.com designates 209.85.216.52 as permitted sender) smtp.mailfrom=zokeefe@google.com; dmarc=pass (policy=reject) header.from=google.com X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: gw57d9gwfdsspczr9z75pqu5kp1jdstc X-HE-Tag: 1657642883-137819 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hey Yang, Thanks for taking the time to review this series again. On Jul 11 14:32, Yang Shi wrote: > On Wed, Jul 6, 2022 at 5:06 PM Zach O'Keefe wrote: > > > > Add a tracepoint to expose mm, address, and enum scan_result of each > > hugepage attempted to be collapsed by call to madvise(MADV_COLLAPSE). > > Is this necessary? Isn't mm_khugepaged_scan_pmd tracepoint good > enough? It doesn't have "address", but you should be able to calculate > address from it with syscall trace together. > I've also found this useful debugging along the file path. Perhaps the answer to that is: add tracepoints to the file path - and we should probably do that - but the other issue is that turning on these tracepoints (for the purposes of debugging MADV_COLLAPSE) generates a lot of noise from khugepaged that is hard to separate out. Augmenting existing tracepoints with .is_khugepaged data incurred the risks associated with altering an existing kernel API. WDYT? Thanks again, Zach > > > > > Signed-off-by: Zach O'Keefe > > --- > > include/trace/events/huge_memory.h | 22 ++++++++++++++++++++++ > > mm/khugepaged.c | 2 ++ > > 2 files changed, 24 insertions(+) > > > > diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h > > index 55392bf30a03..38d339ffdb16 100644 > > --- a/include/trace/events/huge_memory.h > > +++ b/include/trace/events/huge_memory.h > > @@ -167,5 +167,27 @@ TRACE_EVENT(mm_collapse_huge_page_swapin, > > __entry->ret) > > ); > > > > +TRACE_EVENT(mm_madvise_collapse, > > + > > + TP_PROTO(struct mm_struct *mm, unsigned long addr, int result), > > + > > + TP_ARGS(mm, addr, result), > > + > > + TP_STRUCT__entry(__field(struct mm_struct *, mm) > > + __field(unsigned long, addr) > > + __field(int, result) > > + ), > > + > > + TP_fast_assign(__entry->mm = mm; > > + __entry->addr = addr; > > + __entry->result = result; > > + ), > > + > > + TP_printk("mm=%p addr=%#lx result=%s", > > + __entry->mm, > > + __entry->addr, > > + __print_symbolic(__entry->result, SCAN_STATUS)) > > +); > > + > > #endif /* __HUGE_MEMORY_H */ > > #include > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > > index e0d00180512c..0207fc0a5b2a 100644 > > --- a/mm/khugepaged.c > > +++ b/mm/khugepaged.c > > @@ -2438,6 +2438,8 @@ int madvise_collapse(struct vm_area_struct *vma, struct vm_area_struct **prev, > > if (!mmap_locked) > > *prev = NULL; /* Tell caller we dropped mmap_lock */ > > > > + trace_mm_madvise_collapse(mm, addr, result); > > + > > switch (result) { > > case SCAN_SUCCEED: > > case SCAN_PMD_MAPPED: > > -- > > 2.37.0.rc0.161.g10f37bed90-goog > >