From: "Joel Fernandes (Google)" <joel@joelfernandes.org> To: linux-kernel@vger.kernel.org Cc: "Joel Fernandes (Google)" <joel@joelfernandes.org>, Alexey Dobriyan <adobriyan@gmail.com>, Andrew Morton <akpm@linux-foundation.org>, Borislav Petkov <bp@alien8.de>, Brendan Gregg <bgregg@netflix.com>, Catalin Marinas <catalin.marinas@arm.com>, Christian Hansen <chansen3@cisco.com>, dancol@google.com, fmayer@google.com, "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>, joelaf@google.com, Jonathan Corbet <corbet@lwn.net>, Kees Cook <keescook@chromium.org>, 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 <mhocko@suse.com>, Mike Rapoport <rppt@linux.ibm.com>, minchan@kernel.org, namhyung@google.com, paulmck@linux.ibm.com, Robin Murphy <robin.murphy@arm.com>, Roman Gushchin <guro@fb.com>, Stephen Rothwell <sfr@canb.auug.org.au>, surenb@google.com, Thomas Gleixner <tglx@linutronix.de>, tkjos@google.com, Vladimir Davydov <vdavydov.dev@gmail.com>, Vlastimil Babka <vbabka@suse.cz>, Will Deacon <will@kernel.org> Subject: [PATCH v5 5/6] page_idle: Drain all LRU pagevec before idle tracking Date: Wed, 7 Aug 2019 13:15:58 -0400 [thread overview] Message-ID: <20190807171559.182301-5-joel@joelfernandes.org> (raw) In-Reply-To: <20190807171559.182301-1-joel@joelfernandes.org> 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) <joel@joelfernandes.org> --- 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
WARNING: multiple messages have this Message-ID (diff)
From: "Joel Fernandes (Google)" <joel@joelfernandes.org> To: linux-kernel@vger.kernel.org Cc: "Joel Fernandes (Google)" <joel@joelfernandes.org>, Alexey Dobriyan <adobriyan@gmail.com>, Andrew Morton <akpm@linux-foundation.org>, Borislav Petkov <bp@alien8.de>, Brendan Gregg <bgregg@netflix.com>, Catalin Marinas <catalin.marinas@arm.com>, Christian Hansen <chansen3@cisco.com>, dancol@google.com, fmayer@google.com, "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>, joelaf@google.com, Jonathan Corbet <corbet@lwn.net>, Kees Cook <keescook@chromium.org>, 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 <mhocko@suse.com>, Mike Rapoport <rppt@linux.ibm.com>, minchan@kernel.org, namhyung@google.com, paulmck@linux.ibm.com, Robin Murphy <robin.murphy@arm> Subject: [PATCH v5 5/6] page_idle: Drain all LRU pagevec before idle tracking Date: Wed, 7 Aug 2019 13:15:58 -0400 [thread overview] Message-ID: <20190807171559.182301-5-joel@joelfernandes.org> (raw) In-Reply-To: <20190807171559.182301-1-joel@joelfernandes.org> 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) <joel@joelfernandes.org> --- 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
next prev parent reply other threads:[~2019-08-07 17:16 UTC|newest] Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-08-07 17:15 [PATCH v5 1/6] mm/page_idle: Add per-pid idle page tracking using virtual index Joel Fernandes (Google) 2019-08-07 17:15 ` Joel Fernandes (Google) 2019-08-07 17:15 ` [PATCH v5 2/6] mm/page_idle: Add support for handling swapped PG_Idle pages Joel Fernandes (Google) 2019-08-07 17:15 ` Joel Fernandes (Google) 2019-08-13 15:04 ` Michal Hocko 2019-08-13 15:04 ` Michal Hocko 2019-08-13 15:36 ` Joel Fernandes 2019-08-13 15:36 ` Joel Fernandes 2019-08-13 19:24 ` Konstantin Khlebnikov 2019-08-13 19:24 ` Konstantin Khlebnikov 2019-08-14 8:05 ` Michal Hocko 2019-08-14 8:05 ` Michal Hocko 2019-08-14 16:32 ` Joel Fernandes 2019-08-14 16:32 ` Joel Fernandes 2019-08-14 18:36 ` Michal Hocko 2019-08-14 18:36 ` Michal Hocko 2019-08-07 17:15 ` [PATCH v5 3/6] [RFC] x86: Add support for idle bit in swap PTE Joel Fernandes (Google) 2019-08-07 17:15 ` Joel Fernandes (Google) 2019-08-07 17:15 ` [PATCH v5 4/6] [RFC] arm64: " Joel Fernandes (Google) 2019-08-07 17:15 ` Joel Fernandes (Google) 2019-08-07 17:15 ` Joel Fernandes (Google) [this message] 2019-08-07 17:15 ` [PATCH v5 5/6] page_idle: Drain all LRU pagevec before idle tracking Joel Fernandes (Google) 2019-08-07 17:15 ` [PATCH v5 6/6] doc: Update documentation for page_idle virtual address indexing Joel Fernandes (Google) 2019-08-07 17:15 ` Joel Fernandes (Google) 2019-08-07 20:04 ` [PATCH v5 1/6] mm/page_idle: Add per-pid idle page tracking using virtual index Andrew Morton 2019-08-07 20:04 ` Andrew Morton 2019-08-07 20:45 ` Joel Fernandes 2019-08-07 20:45 ` Joel Fernandes 2019-08-07 20:58 ` Andrew Morton 2019-08-07 20:58 ` Andrew Morton 2019-08-07 21:31 ` Joel Fernandes 2019-08-07 21:31 ` Joel Fernandes 2019-08-07 21:55 ` Joel Fernandes 2019-08-07 21:55 ` Joel Fernandes 2019-08-08 8:00 ` Michal Hocko 2019-08-08 8:00 ` Michal Hocko 2019-08-12 14:56 ` Joel Fernandes 2019-08-12 14:56 ` Joel Fernandes 2019-08-13 9:14 ` Michal Hocko 2019-08-13 9:14 ` Michal Hocko 2019-08-13 13:51 ` Joel Fernandes 2019-08-13 13:51 ` Joel Fernandes 2019-08-13 14:14 ` Michal Hocko 2019-08-13 14:14 ` Michal Hocko 2019-08-13 14:45 ` Joel Fernandes 2019-08-13 14:45 ` Joel Fernandes 2019-08-13 14:57 ` Michal Hocko 2019-08-13 14:57 ` Michal Hocko 2019-08-12 18:14 ` Jann Horn 2019-08-12 18:14 ` Jann Horn 2019-08-12 18:14 ` Jann Horn 2019-08-13 10:08 ` Michal Hocko 2019-08-13 10:08 ` Michal Hocko 2019-08-13 14:25 ` Joel Fernandes 2019-08-13 14:25 ` Joel Fernandes 2019-08-13 15:19 ` Jann Horn 2019-08-13 15:19 ` Jann Horn 2019-08-13 15:19 ` Jann Horn 2019-08-13 15:29 ` Jann Horn 2019-08-13 15:29 ` Jann Horn 2019-08-13 15:29 ` Jann Horn 2019-08-13 15:34 ` Daniel Gruss 2019-08-13 15:34 ` Daniel Gruss 2019-08-13 19:18 ` Joel Fernandes 2019-08-13 19:18 ` Joel Fernandes 2019-08-14 7:56 ` Michal Hocko 2019-08-14 7:56 ` Michal Hocko 2019-08-19 21:52 ` Joel Fernandes 2019-08-19 21:52 ` Joel Fernandes 2019-08-13 15:30 ` Joel Fernandes 2019-08-13 15:30 ` Joel Fernandes 2019-08-13 15:40 ` Jann Horn 2019-08-13 15:40 ` Jann Horn 2019-08-13 15:40 ` Jann Horn
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