linux-kernel - [RFC PATCH v6 0/5] Thread-local ABI system call (CPU number cache)

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Date:	Mon,  4 Apr 2016 13:01:48 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Russell King <linux@....linux.org.uk>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>
Cc:	linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
	Paul Turner <pjt@...gle.com>, Andrew Hunter <ahh@...gle.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Andy Lutomirski <luto@...capital.net>,
	Andi Kleen <andi@...stfloor.org>,
	Dave Watson <davejwatson@...com>, Chris Lameter <cl@...ux.com>,
	Ben Maurer <bmaurer@...com>,
	Steven Rostedt <rostedt@...dmis.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Josh Triplett <josh@...htriplett.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	Boqun Feng <boqun.feng@...il.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: [RFC PATCH v6 0/5] Thread-local ABI system call (CPU number cache)

Hi,

This patchset implements a general ABI to exchange per-thread data
between kernel and user-space. The initial feature implemented is a
cache for the CPU number of the currently running thread in user-space.
This ABI is extensible to add more features in the future.

Benchmarks comparing this approach to a getcpu based on system call on
ARM show a 44x speedup. They show a 16.5x speedup on x86-64 compared to
executing lsl from a vDSO through glibc.

There is a man page in the changelog of patch 1/5, which shows an
example usage of this new system call.

This patchset is sent as RFC. It applies on Linux 4.5. The prior
versions of this patchset were known as a "getcpu_cache system call".

Feedback is welcome,

Thanks!

Mathieu


Mathieu Desnoyers (5):
  Thread-local ABI system call: cache CPU number of running thread
  Thread-local ABI cpu_id: ARM resume notifier
  Thread-local ABI: wire up ARM system call
  Thread-local ABI cpu_id: x86 32/64 resume notifier
  Thread-local ABI: wire up x86 32/64 system call

 MAINTAINERS                            |   7 +++
 arch/arm/include/asm/unistd.h          |   2 +-
 arch/arm/include/uapi/asm/unistd.h     |   1 +
 arch/arm/kernel/calls.S                |   3 +-
 arch/arm/kernel/signal.c               |   1 +
 arch/x86/entry/common.c                |   1 +
 arch/x86/entry/syscalls/syscall_32.tbl |   1 +
 arch/x86/entry/syscalls/syscall_64.tbl |   1 +
 fs/exec.c                              |   1 +
 include/linux/sched.h                  |  66 +++++++++++++++++++++
 include/uapi/linux/Kbuild              |   1 +
 include/uapi/linux/thread_local_abi.h  |  83 ++++++++++++++++++++++++++
 init/Kconfig                           |  14 +++++
 kernel/Makefile                        |   1 +
 kernel/fork.c                          |   4 ++
 kernel/sched/sched.h                   |   1 +
 kernel/sys_ni.c                        |   3 +
 kernel/thread_local_abi.c              | 103 +++++++++++++++++++++++++++++++++
 18 files changed, 292 insertions(+), 2 deletions(-)
 create mode 100644 include/uapi/linux/thread_local_abi.h
 create mode 100644 kernel/thread_local_abi.c

-- 
2.1.4