From: Michal Hocko <mhocko@kernel.org> To: Andrew Morton <akpm@linux-foundation.org> Cc: <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>, Michal Hocko <mhocko@suse.com>, David Hildenbrand <david@redhat.com>, Hugh Dickins <hughd@google.com>, Jan Kara <jack@suse.cz>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, William Kucharski <william.kucharski@oracle.com> Subject: [PATCH 3/3] mm, fault_around: do not take a reference to a locked page Date: Tue, 11 Dec 2018 15:27:41 +0100 [thread overview] Message-ID: <20181211142741.2607-4-mhocko@kernel.org> (raw) In-Reply-To: <20181211142741.2607-1-mhocko@kernel.org> From: Michal Hocko <mhocko@suse.com> filemap_map_pages takes a speculative reference to each page in the range before it tries to lock that page. While this is correct it also can influence page migration which will bail out when seeing an elevated reference count. The faultaround code would bail on seeing a locked page so we can pro-actively check the PageLocked bit before page_cache_get_speculative and prevent from pointless reference count churn. Suggested-by: Jan Kara <jack@suse.cz> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Reviewed-by: David Hildenbrand <david@redhat.com> Acked-by: Hugh Dickins <hughd@google.com> Reviewed-by: William Kucharski <william.kucharski@oracle.com> Signed-off-by: Michal Hocko <mhocko@suse.com> --- mm/filemap.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/mm/filemap.c b/mm/filemap.c index 81adec8ee02c..a87f71fff879 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2553,6 +2553,13 @@ void filemap_map_pages(struct vm_fault *vmf, goto next; head = compound_head(page); + + /* + * Check for a locked page first, as a speculative + * reference may adversely influence page migration. + */ + if (PageLocked(head)) + goto next; if (!page_cache_get_speculative(head)) goto next; -- 2.19.2
WARNING: multiple messages have this Message-ID (diff)
From: Michal Hocko <mhocko@kernel.org> To: Andrew Morton <akpm@linux-foundation.org> Cc: linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>, Michal Hocko <mhocko@suse.com>, David Hildenbrand <david@redhat.com>, Hugh Dickins <hughd@google.com>, Jan Kara <jack@suse.cz>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, William Kucharski <william.kucharski@oracle.com> Subject: [PATCH 3/3] mm, fault_around: do not take a reference to a locked page Date: Tue, 11 Dec 2018 15:27:41 +0100 [thread overview] Message-ID: <20181211142741.2607-4-mhocko@kernel.org> (raw) In-Reply-To: <20181211142741.2607-1-mhocko@kernel.org> From: Michal Hocko <mhocko@suse.com> filemap_map_pages takes a speculative reference to each page in the range before it tries to lock that page. While this is correct it also can influence page migration which will bail out when seeing an elevated reference count. The faultaround code would bail on seeing a locked page so we can pro-actively check the PageLocked bit before page_cache_get_speculative and prevent from pointless reference count churn. Suggested-by: Jan Kara <jack@suse.cz> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Reviewed-by: David Hildenbrand <david@redhat.com> Acked-by: Hugh Dickins <hughd@google.com> Reviewed-by: William Kucharski <william.kucharski@oracle.com> Signed-off-by: Michal Hocko <mhocko@suse.com> --- mm/filemap.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/mm/filemap.c b/mm/filemap.c index 81adec8ee02c..a87f71fff879 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2553,6 +2553,13 @@ void filemap_map_pages(struct vm_fault *vmf, goto next; head = compound_head(page); + + /* + * Check for a locked page first, as a speculative + * reference may adversely influence page migration. + */ + if (PageLocked(head)) + goto next; if (!page_cache_get_speculative(head)) goto next; -- 2.19.2
next prev parent reply other threads:[~2018-12-11 14:27 UTC|newest] Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-12-11 14:27 [PATCH 0/3] few memory offlining enhancements Michal Hocko 2018-12-11 14:27 ` Michal Hocko 2018-12-11 14:27 ` [PATCH 1/3] mm, memory_hotplug: try to migrate full pfn range Michal Hocko 2018-12-11 14:27 ` Michal Hocko 2018-12-12 1:12 ` Wei Yang 2018-12-11 14:27 ` [PATCH 2/3] mm, memory_hotplug: deobfuscate migration part of offlining Michal Hocko 2018-12-11 14:27 ` Michal Hocko 2018-12-11 14:27 ` Michal Hocko [this message] 2018-12-11 14:27 ` [PATCH 3/3] mm, fault_around: do not take a reference to a locked page Michal Hocko
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