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[209.85.220.65]) by mx.google.com with SMTPS id ca12sor819380pjb.6.2019.08.07.10.16.24 for (Google Transport Security); Wed, 07 Aug 2019 10:16:24 -0700 (PDT) Received-SPF: pass (google.com: domain of joel@joelfernandes.org designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@joelfernandes.org header.s=google header.b=cpS86uEm; spf=pass (google.com: domain of joel@joelfernandes.org designates 209.85.220.65 as permitted sender) smtp.mailfrom=joel@joelfernandes.org DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=xT1EUv7l9ELnBbW3Pj9GyH6zMTpmJcDHOSB5E5y40eQ=; b=cpS86uEmYIzhxFzCySaqqOeImVDTWodZUXCQVQcRGqqRAGGDs1sNZw0oH3tmy2iZOE XkIu9l2OhfxN0xt6NyH+lVLF+8mXgqz7NSPIIJ+egtHoGZEtUgQY7iySTu1NQl565je/ qL/IqLU05tBxt6AwDFcVVWZEJCirczwMCOG/I= X-Google-Smtp-Source: APXvYqwugi3AW6n6dfP+TB/Uc5APuLJqoUYRpEzJ6Mn8Htn03idxWxXllDnzug9Hw6aLl8p384B8Ag== X-Received: by 2002:a17:90a:1785:: with SMTP id q5mr950338pja.106.1565198183794; Wed, 07 Aug 2019 10:16:23 -0700 (PDT) Received: from joelaf.cam.corp.google.com ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id a1sm62692130pgh.61.2019.08.07.10.16.20 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Wed, 07 Aug 2019 10:16:23 -0700 (PDT) From: "Joel Fernandes (Google)" To: linux-kernel@vger.kernel.org Cc: "Joel Fernandes (Google)" , Alexey Dobriyan , Andrew Morton , Borislav Petkov , Brendan Gregg , Catalin Marinas , Christian Hansen , dancol@google.com, fmayer@google.com, "H. Peter Anvin" , Ingo Molnar , joelaf@google.com, Jonathan Corbet , Kees Cook , kernel-team@android.com, linux-api@vger.kernel.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Michal Hocko , Mike Rapoport , minchan@kernel.org, namhyung@google.com, paulmck@linux.ibm.com, Robin Murphy , Roman Gushchin , Stephen Rothwell , surenb@google.com, Thomas Gleixner , tkjos@google.com, Vladimir Davydov , Vlastimil Babka , Will Deacon Subject: [PATCH v5 5/6] page_idle: Drain all LRU pagevec before idle tracking Date: Wed, 7 Aug 2019 13:15:58 -0400 Message-Id: <20190807171559.182301-5-joel@joelfernandes.org> X-Mailer: git-send-email 2.22.0.770.g0f2c4a37fd-goog In-Reply-To: <20190807171559.182301-1-joel@joelfernandes.org> References: <20190807171559.182301-1-joel@joelfernandes.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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: During idle page tracking, we see that sometimes faulted anon pages are in pagevec but are not drained to LRU. Idle page tracking only considers pages on LRU. I am able to find multiple issues involving this. One issue looks like idle tracking is completely broken. It shows up in my testing as if a page that is marked as idle is always "accessed" -- because it was never marked as idle (due to not draining of pagevec). The other issue shows up as a failure during swapping (support for which this series adds), with the following sequence: 1. Allocate some pages 2. Write to them 3. Mark them as idle <--- fails 4. Introduce some memory pressure to induce swapping. 5. Check the swap bit I introduced in this series. <--- fails to set idle bit in swap PTE. To fix this, this patch drains all CPU's pagevec before starting idle tracking. Signed-off-by: Joel Fernandes (Google) --- mm/page_idle.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/mm/page_idle.c b/mm/page_idle.c index 2766d4ab348c..26440a497609 100644 --- a/mm/page_idle.c +++ b/mm/page_idle.c @@ -180,6 +180,13 @@ static ssize_t page_idle_bitmap_read(struct file *file, struct kobject *kobj, unsigned long pfn, end_pfn; int bit, ret; + /* + * Idle page tracking currently works only on LRU pages, so drain + * them. This can cause slowness, but in the future we could + * remove this operation if we are tracking non-LRU pages too. + */ + lru_add_drain_all(); + ret = page_idle_get_frames(pos, count, NULL, &pfn, &end_pfn); if (ret == -ENXIO) return 0; /* Reads beyond max_pfn do nothing */ @@ -211,6 +218,13 @@ static ssize_t page_idle_bitmap_write(struct file *file, struct kobject *kobj, unsigned long pfn, end_pfn; int bit, ret; + /* + * Idle page tracking currently works only on LRU pages, so drain + * them. This can cause slowness, but in the future we could + * remove this operation if we are tracking non-LRU pages too. + */ + lru_add_drain_all(); + ret = page_idle_get_frames(pos, count, NULL, &pfn, &end_pfn); if (ret) return ret; @@ -428,6 +442,13 @@ ssize_t page_idle_proc_generic(struct file *file, char __user *ubuff, walk.private = &priv; walk.mm = mm; + /* + * Idle page tracking currently works only on LRU pages, so drain + * them. This can cause slowness, but in the future we could + * remove this operation if we are tracking non-LRU pages too. + */ + lru_add_drain_all(); + down_read(&mm->mmap_sem); /* -- 2.22.0.770.g0f2c4a37fd-goog