[RFC PATCH 0/3] Implement getcpu_cache system call

[Mathieu Desnoyers <mathieu.desnoyers@efficios.com>]

Hi,

Here is a patchset implementing a cache for the CPU number of the
currently running thread in user-space.

Benchmarks comparing this approach to a system call-based getcpu on ARM
show a 44x speedup. They show a 14x speedup on x86-64 compared to
executing lsl from a vDSO through glibc.

I'm added a man page in the changelog of patch 1/3, which shows an
example usage of this new system call.

This patchset is sent as RFC. It applies on Linux 4.3.

Feedback is welcome,

Thanks!

Mathieu

Mathieu Desnoyers (3):
  getcpu_cache system call: cache CPU number of running thread
  getcpu_cache: wire up ARM system call
  getcpu_cache: wire up x86 32/64 system call

 arch/arm/include/uapi/asm/unistd.h     |   1 +
 arch/arm/kernel/calls.S                |   1 +
 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/init_task.h              |   8 ++
 include/linux/sched.h                  |  43 +++++++++
 include/uapi/linux/Kbuild              |   1 +
 include/uapi/linux/getcpu_cache.h      |  44 +++++++++
 init/Kconfig                           |  10 ++
 kernel/Makefile                        |   1 +
 kernel/fork.c                          |   7 ++
 kernel/getcpu_cache.c                  | 170 +++++++++++++++++++++++++++++++++
 kernel/sched/core.c                    |   3 +
 kernel/sched/sched.h                   |   1 +
 kernel/sys_ni.c                        |   3 +
 18 files changed, 298 insertions(+)
 create mode 100644 include/uapi/linux/getcpu_cache.h
 create mode 100644 kernel/getcpu_cache.c

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2.1.4