1. 06 Nov, 2015 2 commits
  2. 14 Oct, 2015 1 commit
  3. 10 Sep, 2015 1 commit
    • Vladimir Davydov's avatar
      mm: introduce idle page tracking · 33c3fc71
      Vladimir Davydov authored
      
      
      Knowing the portion of memory that is not used by a certain application or
      memory cgroup (idle memory) can be useful for partitioning the system
      efficiently, e.g.  by setting memory cgroup limits appropriately.
      Currently, the only means to estimate the amount of idle memory provided
      by the kernel is /proc/PID/{clear_refs,smaps}: the user can clear the
      access bit for all pages mapped to a particular process by writing 1 to
      clear_refs, wait for some time, and then count smaps:Referenced.  However,
      this method has two serious shortcomings:
      
       - it does not count unmapped file pages
       - it affects the reclaimer logic
      
      To overcome these drawbacks, this patch introduces two new page flags,
      Idle and Young, and a new sysfs file, /sys/kernel/mm/page_idle/bitmap.
      A page's Idle flag can only be set from userspace by setting bit in
      /sys/kernel/mm/page_idle/bitmap at the offset corresponding to the page,
      and it is cleared whenever the page is accessed either through page tables
      (it is cleared in page_referenced() in this case) or using the read(2)
      system call (mark_page_accessed()). Thus by setting the Idle flag for
      pages of a particular workload, which can be found e.g.  by reading
      /proc/PID/pagemap, waiting for some time to let the workload access its
      working set, and then reading the bitmap file, one can estimate the amount
      of pages that are not used by the workload.
      
      The Young page flag is used to avoid interference with the memory
      reclaimer.  A page's Young flag is set whenever the Access bit of a page
      table entry pointing to the page is cleared by writing to the bitmap file.
      If page_referenced() is called on a Young page, it will add 1 to its
      return value, therefore concealing the fact that the Access bit was
      cleared.
      
      Note, since there is no room for extra page flags on 32 bit, this feature
      uses extended page flags when compiled on 32 bit.
      
      [akpm@linux-foundation.org: fix build]
      [akpm@linux-foundation.org: kpageidle requires an MMU]
      [akpm@linux-foundation.org: decouple from page-flags rework]
      Signed-off-by: default avatarVladimir Davydov <vdavydov@parallels.com>
      Reviewed-by: default avatarAndres Lagar-Cavilla <andreslc@google.com>
      Cc: Minchan Kim <minchan@kernel.org>
      Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Greg Thelen <gthelen@google.com>
      Cc: Michel Lespinasse <walken@google.com>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Pavel Emelyanov <xemul@parallels.com>
      Cc: Cyrill Gorcunov <gorcunov@openvz.org>
      Cc: Jonathan Corbet <corbet@lwn.net>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      33c3fc71
  4. 08 Sep, 2015 6 commits
  5. 04 Sep, 2015 1 commit
    • Andrea Arcangeli's avatar
      userfaultfd: add VM_UFFD_MISSING and VM_UFFD_WP · 16ba6f81
      Andrea Arcangeli authored
      
      
      These two flags gets set in vma->vm_flags to tell the VM common code
      if the userfaultfd is armed and in which mode (only tracking missing
      faults, only tracking wrprotect faults or both). If neither flags is
      set it means the userfaultfd is not armed on the vma.
      Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Acked-by: default avatarPavel Emelyanov <xemul@parallels.com>
      Cc: Sanidhya Kashyap <sanidhya.gatech@gmail.com>
      Cc: zhang.zhanghailiang@huawei.com
      Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
      Cc: Andres Lagar-Cavilla <andreslc@google.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Paolo Bonzini <pbonzini@redhat.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Peter Feiner <pfeiner@google.com>
      Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      16ba6f81
  6. 23 Jun, 2015 1 commit
  7. 17 Mar, 2015 1 commit
  8. 13 Feb, 2015 2 commits
  9. 12 Feb, 2015 9 commits
  10. 10 Feb, 2015 1 commit
  11. 11 Dec, 2014 1 commit
  12. 17 Nov, 2014 1 commit
    • Qiaowei Ren's avatar
      x86, mpx: Introduce VM_MPX to indicate that a VMA is MPX specific · 4aae7e43
      Qiaowei Ren authored
      
      
      MPX-enabled applications using large swaths of memory can
      potentially have large numbers of bounds tables in process
      address space to save bounds information. These tables can take
      up huge swaths of memory (as much as 80% of the memory on the
      system) even if we clean them up aggressively. In the worst-case
      scenario, the tables can be 4x the size of the data structure
      being tracked. IOW, a 1-page structure can require 4 bounds-table
      pages.
      
      Being this huge, our expectation is that folks using MPX are
      going to be keen on figuring out how much memory is being
      dedicated to it. So we need a way to track memory use for MPX.
      
      If we want to specifically track MPX VMAs we need to be able to
      distinguish them from normal VMAs, and keep them from getting
      merged with normal VMAs. A new VM_ flag set only on MPX VMAs does
      both of those things. With this flag, MPX bounds-table VMAs can
      be distinguished from other VMAs, and userspace can also walk
      /proc/$pid/smaps to get memory usage for MPX.
      
      In addition to this flag, we also introduce a special ->vm_ops
      specific to MPX VMAs (see the patch "add MPX specific mmap
      interface"), but currently different ->vm_ops do not by
      themselves prevent VMA merging, so we still need this flag.
      
      We understand that VM_ flags are scarce and are open to other
      options.
      Signed-off-by: default avatarQiaowei Ren <qiaowei.ren@intel.com>
      Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
      Cc: linux-mm@kvack.org
      Cc: linux-mips@linux-mips.org
      Cc: Dave Hansen <dave@sr71.net>
      Link: http://lkml.kernel.org/r/20141114151825.565625B3@viggo.jf.intel.com
      
      Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      4aae7e43
  13. 14 Oct, 2014 1 commit
    • Peter Feiner's avatar
      mm: softdirty: enable write notifications on VMAs after VM_SOFTDIRTY cleared · 64e45507
      Peter Feiner authored
      For VMAs that don't want write notifications, PTEs created for read faults
      have their write bit set.  If the read fault happens after VM_SOFTDIRTY is
      cleared, then the PTE's softdirty bit will remain clear after subsequent
      writes.
      
      Here's a simple code snippet to demonstrate the bug:
      
        char* m = mmap(NULL, getpagesize(), PROT_READ | PROT_WRITE,
                       MAP_ANONYMOUS | MAP_SHARED, -1, 0);
        system("echo 4 > /proc/$PPID/clear_refs"); /* clear VM_SOFTDIRTY */
        assert(*m == '\0');     /* new PTE allows write access */
        assert(!soft_dirty(x));
        *m = 'x';               /* should dirty the page */
        assert(soft_dirty(x));  /* fails */
      
      With this patch, write notifications are enabled when VM_SOFTDIRTY is
      cleared.  Furthermore, to avoid unnecessary faults, write notifications
      are disabled when VM_SOFTDIRTY is set.
      
      As a side effect of enabling and disabling write notifications with
      care, this patch fixes a bug in mprotect where vm_page_prot bits set by
      drivers were zapped on mprotect.  An analogous bug was fixed in mmap by
      commit c9d0bf24
      
       ("mm: uncached vma support with writenotify").
      Signed-off-by: default avatarPeter Feiner <pfeiner@google.com>
      Reported-by: default avatarPeter Feiner <pfeiner@google.com>
      Suggested-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
      Cc: Cyrill Gorcunov <gorcunov@openvz.org>
      Cc: Pavel Emelyanov <xemul@parallels.com>
      Cc: Jamie Liu <jamieliu@google.com>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
      Cc: Bjorn Helgaas <bhelgaas@google.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      64e45507
  14. 10 Oct, 2014 12 commits