linux-toradex.git/include/linux/mmu_notifier.h, branch v4.6-rc3

mm: introduce idle page tracking

2015-09-10T20:29:01+00:00

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: Vladimir Davydov 
Reviewed-by: Andres Lagar-Cavilla 
Cc: Minchan Kim 
Cc: Raghavendra K T 
Cc: Johannes Weiner 
Cc: Michal Hocko 
Cc: Greg Thelen 
Cc: Michel Lespinasse 
Cc: David Rientjes 
Cc: Pavel Emelyanov 
Cc: Cyrill Gorcunov 
Cc: Jonathan Corbet 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mmu-notifier: add clear_young callback

2015-09-10T20:29:01+00:00

In the scope of the idle memory tracking feature, which is introduced by
the following patch, we need to clear the referenced/accessed bit not only
in primary, but also in secondary ptes.  The latter is required in order
to estimate wss of KVM VMs.  At the same time we want to avoid flushing
tlb, because it is quite expensive and it won't really affect the final
result.

Currently, there is no function for clearing pte young bit that would meet
our requirements, so this patch introduces one.  To achieve that we have
to add a new mmu-notifier callback, clear_young, since there is no method
for testing-and-clearing a secondary pte w/o flushing tlb.  The new method
is not mandatory and currently only implemented by KVM.

Signed-off-by: Vladimir Davydov 
Reviewed-by: Andres Lagar-Cavilla 
Acked-by: Paolo Bonzini 
Cc: Minchan Kim 
Cc: Raghavendra K T 
Cc: Johannes Weiner 
Cc: Michal Hocko 
Cc: Greg Thelen 
Cc: Michel Lespinasse 
Cc: David Rientjes 
Cc: Pavel Emelyanov 
Cc: Cyrill Gorcunov 
Cc: Jonathan Corbet 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: clarify that the function operates on hugepage pte

2015-06-25T00:49:44+00:00

We have confusing functions to clear pmd, pmd_clear_* and pmd_clear.  Add
_huge_ to pmdp_clear functions so that we are clear that they operate on
hugepage pte.

We don't bother about other functions like pmdp_set_wrprotect,
pmdp_clear_flush_young, because they operate on PTE bits and hence
indicate they are operating on hugepage ptes

Signed-off-by: Aneesh Kumar K.V 
Acked-by: Kirill A. Shutemov 
Cc: Benjamin Herrenschmidt 
Cc: Paul Mackerras 
Cc: Michael Ellerman 
Cc: Andrea Arcangeli 
Cc: Martin Schwidefsky 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'drm-next' of git://people.freedesktop.org/~airlied/linux

2014-12-15T23:52:01+00:00

Pull drm updates from Dave Airlie:
 "Highlights:

   - AMD KFD driver merge

     This is the AMD HSA interface for exposing a lowlevel interface for
     GPGPU use.  They have an open source userspace built on top of this
     interface, and the code looks as good as it was going to get out of
     tree.

   - Initial atomic modesetting work

     The need for an atomic modesetting interface to allow userspace to
     try and send a complete set of modesetting state to the driver has
     arisen, and been suffering from neglect this past year.  No more,
     the start of the common code and changes for msm driver to use it
     are in this tree.  Ongoing work to get the userspace ioctl finished
     and the code clean will probably wait until next kernel.

   - DisplayID 1.3 and tiled monitor exposed to userspace.

     Tiled monitor property is now exposed for userspace to make use of.

   - Rockchip drm driver merged.

   - imx gpu driver moved out of staging

  Other stuff:

   - core:
        panel - MIPI DSI + new panels.
        expose suggested x/y properties for virtual GPUs

   - i915:
        Initial Skylake (SKL) support
        gen3/4 reset work
        start of dri1/ums removal
        infoframe tracking
        fixes for lots of things.

   - nouveau:
        tegra k1 voltage support
        GM204 modesetting support
        GT21x memory reclocking work

   - radeon:
        CI dpm fixes
        GPUVM improvements
        Initial DPM fan control

   - rcar-du:
        HDMI support added
        removed some support for old boards
        slave encoder driver for Analog Devices adv7511

   - exynos:
        Exynos4415 SoC support

   - msm:
        a4xx gpu support
        atomic helper conversion

   - tegra:
        iommu support
        universal plane support
        ganged-mode DSI support

   - sti:
        HDMI i2c improvements

   - vmwgfx:
        some late fixes.

   - qxl:
        use suggested x/y properties"

* 'drm-next' of git://people.freedesktop.org/~airlied/linux: (969 commits)
  drm: sti: fix module compilation issue
  drm/i915: save/restore GMBUS freq across suspend/resume on gen4
  drm: sti: correctly cleanup CRTC and planes
  drm: sti: add HQVDP plane
  drm: sti: add cursor plane
  drm: sti: enable auxiliary CRTC
  drm: sti: fix delay in VTG programming
  drm: sti: prepare sti_tvout to support auxiliary crtc
  drm: sti: use drm_crtc_vblank_{on/off} instead of drm_vblank_{on/off}
  drm: sti: fix hdmi avi infoframe
  drm: sti: remove event lock while disabling vblank
  drm: sti: simplify gdp code
  drm: sti: clear all mixer control
  drm: sti: remove gpio for HDMI hot plug detection
  drm: sti: allow to change hdmi ddc i2c adapter
  drm/doc: Document drm_add_modes_noedid() usage
  drm/i915: Remove '& 0xffff' from the mask given to WA_REG()
  drm/i915: Invert the mask and val arguments in wa_add() and WA_REG()
  drm: Zero out DRM object memory upon cleanup
  drm/i915/bdw: Fix the write setting up the WIZ hashing mode
  ...

mm: convert i_mmap_mutex to rwsem

2014-12-13T20:42:45+00:00

The i_mmap_mutex is a close cousin of the anon vma lock, both protecting
similar data, one for file backed pages and the other for anon memory.  To
this end, this lock can also be a rwsem.  In addition, there are some
important opportunities to share the lock when there are no tree
modifications.

This conversion is straightforward.  For now, all users take the write
lock.

[sfr@canb.auug.org.au: update fremap.c]
Signed-off-by: Davidlohr Bueso 
Reviewed-by: Rik van Riel 
Acked-by: "Kirill A. Shutemov" 
Acked-by: Hugh Dickins 
Cc: Oleg Nesterov 
Acked-by: Peter Zijlstra (Intel) 
Cc: Srikar Dronamraju 
Acked-by: Mel Gorman 
Signed-off-by: Stephen Rothwell 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kvm: Fix page ageing bugs

2014-09-24T12:07:58+00:00

1. We were calling clear_flush_young_notify in unmap_one, but we are
within an mmu notifier invalidate range scope. The spte exists no more
(due to range_start) and the accessed bit info has already been
propagated (due to kvm_pfn_set_accessed). Simply call
clear_flush_young.

2. We clear_flush_young on a primary MMU PMD, but this may be mapped
as a collection of PTEs by the secondary MMU (e.g. during log-dirty).
This required expanding the interface of the clear_flush_young mmu
notifier, so a lot of code has been trivially touched.

3. In the absence of shadow_accessed_mask (e.g. EPT A bit), we emulate
the access bit by blowing the spte. This requires proper synchronizing
with MMU notifier consumers, like every other removal of spte's does.

Signed-off-by: Andres Lagar-Cavilla 
Acked-by: Rik van Riel 
Signed-off-by: Paolo Bonzini

mmu_notifier: add call_srcu and sync function for listener to delay call and sync

2014-08-07T01:01:22+00:00

When kernel device drivers or subsystems want to bind their lifespan to
t= he lifespan of the mm_struct, they usually use one of the following
methods:

1. Manually calling a function in the interested kernel module.  The
   funct= ion call needs to be placed in mmput.  This method was rejected
   by several ker= nel maintainers.

2. Registering to the mmu notifier release mechanism.

The problem with the latter approach is that the mmu_notifier_release
cal= lback is called from__mmu_notifier_release (called from exit_mmap).
That functi= on iterates over the list of mmu notifiers and don't expect
the release call= back function to remove itself from the list.
Therefore, the callback function= in the kernel module can't release the
mmu_notifier_object, which is actuall= y the kernel module's object
itself.  As a result, the destruction of the kernel module's object must
to be done in a delayed fashion.

This patch adds support for this delayed callback, by adding a new
mmu_notifier_call_srcu function that receives a function ptr and calls
th= at function with call_srcu.  In that function, the kernel module
releases its object.  To use mmu_notifier_call_srcu, the calling module
needs to call b= efore that a new function called
mmu_notifier_unregister_no_release that as its= name implies,
unregisters a notifier without calling its notifier release call= back.

This patch also adds a function that will call barrier_srcu so those
kern= el modules can sync with mmu_notifier.

Signed-off-by: Peter Zijlstra 
Signed-off-by: Jérôme Glisse 
Signed-off-by: Oded Gabbay 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mmu_notifier: add the callback for mmu_notifier_invalidate_range()

2014-11-13T02:46:09+00:00

Now that the mmu_notifier_invalidate_range() calls are in place, add the
callback to allow subsystems to register against it.

Signed-off-by: Joerg Roedel 
Reviewed-by: Andrea Arcangeli 
Reviewed-by: Jérôme Glisse 
Cc: Peter Zijlstra 
Cc: Rik van Riel 
Cc: Hugh Dickins 
Cc: Mel Gorman 
Cc: Johannes Weiner 
Cc: Jay Cornwall 
Cc: Oded Gabbay 
Cc: Suravee Suthikulpanit 
Cc: Jesse Barnes 
Cc: David Woodhouse 
Signed-off-by: Andrew Morton 
Signed-off-by: Oded Gabbay

mmu_notifier: call mmu_notifier_invalidate_range() from VMM

2014-11-13T02:46:09+00:00

Add calls to the new mmu_notifier_invalidate_range() function to all
places in the VMM that need it.

Signed-off-by: Joerg Roedel 
Reviewed-by: Andrea Arcangeli 
Reviewed-by: Jérôme Glisse 
Cc: Peter Zijlstra 
Cc: Rik van Riel 
Cc: Hugh Dickins 
Cc: Mel Gorman 
Cc: Johannes Weiner 
Cc: Jay Cornwall 
Cc: Oded Gabbay 
Cc: Suravee Suthikulpanit 
Cc: Jesse Barnes 
Cc: David Woodhouse 
Signed-off-by: Andrew Morton 
Signed-off-by: Oded Gabbay

mmu_notifier: add mmu_notifier_invalidate_range()

2014-11-13T02:46:09+00:00

This notifier closes an important gap in the current mmu_notifier
implementation, the existing callbacks are called too early or too late to
reliably manage a non-CPU TLB.  Specifically, invalidate_range_start() is
called when all pages are still mapped and invalidate_range_end() when all
pages are unmapped and potentially freed.

This is fine when the users of the mmu_notifiers manage their own SoftTLB,
like KVM does.  When the TLB is managed in software it is easy to wipe out
entries for a given range and prevent new entries to be established until
invalidate_range_end is called.

But when the user of mmu_notifiers has to manage a hardware TLB it can
still wipe out TLB entries in invalidate_range_start, but it can't make
sure that no new TLB entries in the given range are established between
invalidate_range_start and invalidate_range_end.

To avoid silent data corruption the entries in the non-CPU TLB need to be
flushed when the pages are unmapped (at this point in time no _new_ TLB
entries can be established in the non-CPU TLB) but not yet freed (as the
non-CPU TLB may still have _existing_ entries pointing to the pages about
to be freed).

To fix this problem we need to catch the moment when the Linux VMM flushes
remote TLBs (as a non-CPU TLB is not very CPU TLB), as this is the point
in time when the pages are unmapped but _not_ yet freed.

The mmu_notifier_invalidate_range() function aims to catch that moment.

IOMMU code will be one user of the notifier-callback.  Currently this is
only the AMD IOMMUv2 driver, but its code is about to be more generalized
and converted to a generic IOMMU-API extension to fit the needs of similar
functionality in other IOMMUs as well.

The current attempt in the AMD IOMMUv2 driver to work around the
invalidate_range_start/end() shortcoming is to assign an empty page table
to the non-CPU TLB between any invalidata_range_start/end calls.  With the
empty page-table assigned, every page-table walk to re-fill the non-CPU
TLB will cause a page-fault reported to the IOMMU driver via an interrupt,
possibly causing interrupt storms.

The page-fault handler in the AMD IOMMUv2 driver doesn't handle the fault
if an invalidate_range_start/end pair is active, it just reports back
SUCCESS to the device and let it refault the page.  But existing hardware
(newer Radeon GPUs) that makes use of this feature don't re-fault
indefinitly, after a certain number of faults for the same address the
device enters a failure state and needs to be resetted.

To avoid the GPUs entering a failure state we need to get rid of the
empty-page-table workaround and use the mmu_notifier_invalidate_range()
function introduced with this patch.

Signed-off-by: Joerg Roedel 
Reviewed-by: Andrea Arcangeli 
Reviewed-by: Jérôme Glisse 
Cc: Peter Zijlstra 
Cc: Rik van Riel 
Cc: Hugh Dickins 
Cc: Mel Gorman 
Cc: Johannes Weiner 
Cc: Jay Cornwall 
Cc: Oded Gabbay 
Cc: Suravee Suthikulpanit 
Cc: Jesse Barnes 
Cc: David Woodhouse 
Signed-off-by: Andrew Morton 
Signed-off-by: Oded Gabbay