[PATCH 0/2] x86/vdso: Add Hyper-V TSC page clocksource support

Vitaly Kuznetsov
Thu, 09 Feb 2017 14:10:50 -0000

Hi,

Hyper-V TSC page clocksource is suitable for vDSO, however, the protocol
defined by the hypervisor is different from VCLOCK_PVCLOCK. Implemented the
required support. Simple sysbench test shows the following results:

Before:
# time sysbench --test=memory --max-requests=500000 run
...
real    1m22.618s
user    0m50.193s
sys     0m32.268s

After:
# time sysbench --test=memory --max-requests=500000 run
...
real	0m47.241s
user	0m47.117s
sys	0m0.008s

So it seems it is worth it. As nobody seems to be strongly offended by my RFC
I'm sending first non-RFC version. Patch 1 is made on top of K. Y.'s
code
refactoring which moved tsc page clocksource to arch/x86/hyperv/hv_init.c,
this is currently present in Greg's char-misc-next tree.

Changes since RFC:
- Use mul_u64_u64_shr() instead of an open coded implementation
  [Andy Lutomirski, Thomas Gleixner]
- Don't use the same pvclock_page for both VCLOCK_PVCLOCK and
  VCLOCK_HVCLOCK, create another one [Andy Lutomirski]
- Fix issues reported by kbuild test robot.
- Rename HYPERV_CLOCK -> HYPERV_TSCPAGE to avoid the ambiguity.

I'm also going to try to optimize mul_u64_u64_shr() for 32bit but this can
be split from this series I guess.

Vitaly Kuznetsov (2):
  hyperv: implement hv_get_tsc_page()
  x86/vdso: Add VCLOCK_HVCLOCK vDSO clock read method

 arch/x86/entry/vdso/vclock_gettime.c  | 36 +++++++++++++++++++++++++++++++++++
 arch/x86/entry/vdso/vdso-layout.lds.S |  3 ++-
 arch/x86/entry/vdso/vdso2c.c          |  3 +++
 arch/x86/entry/vdso/vma.c             |  7 +++++++
 arch/x86/hyperv/hv_init.c             | 12 ++++++++++--
 arch/x86/include/asm/clocksource.h    |  3 ++-
 arch/x86/include/asm/mshyperv.h       |  8 ++++++++
 arch/x86/include/asm/vdso.h           |  1 +
 drivers/hv/Kconfig                    |  3 +++
 9 files changed, 72 insertions(+), 4 deletions(-)

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2.9.3