linux-kernel - [PATCH v2 0/3] x86/vdso: Add Hyper-V TSC page clocksource support

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Date:   Tue, 14 Feb 2017 13:44:05 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     x86@...nel.org, Andy Lutomirski <luto@...capital.net>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Dexuan Cui <decui@...rosoft.com>, linux-kernel@...r.kernel.org,
        devel@...uxdriverproject.org,
        virtualization@...ts.linux-foundation.org
Subject: [PATCH v2 0/3] x86/vdso: Add Hyper-V TSC page clocksource support

Hi,

while we're still waiting for a definitive ACK from Microsoft that the
algorithm is good for SMP case (as we can't prevent the code in vdso from
migrating between CPUs) I'd like to send v2 with some modifications to keep
the discussion going.

Changes since v1:
- Document the TSC page reading protocol [Thomas Gleixner].

- Separate the TSC page reading code from read_hv_clock_tsc() and put it to
  asm/mshyperv.h to use from both hv_init.c and vdso.

- Add explicit barriers [Thomas Gleixner]

Original description:

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

Patches 1 and 2 are 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.

Vitaly Kuznetsov (3):
  x86/hyperv: implement hv_get_tsc_page()
  x86/hyperv: move TSC reading method to asm/mshyperv.h
  x86/vdso: Add VCLOCK_HVCLOCK vDSO clock read method

 arch/x86/entry/vdso/vclock_gettime.c  | 24 +++++++++++++++
 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             | 48 +++++++++--------------------
 arch/x86/include/asm/clocksource.h    |  3 +-
 arch/x86/include/asm/mshyperv.h       | 58 +++++++++++++++++++++++++++++++++++
 arch/x86/include/asm/vdso.h           |  1 +
 drivers/hv/Kconfig                    |  3 ++
 9 files changed, 114 insertions(+), 36 deletions(-)

-- 
2.9.3