Re: [PATCH v2 2/4] percpu_stats: Enable 64-bit counts in 32-bit architectures

From	Tejun Heo <tj@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2 2/4] percpu_stats: Enable 64-bit counts in 32-bit architectures
Date	2016-04-12 00:20 +0200
Message-ID	<rmSlz-4EU-1@gated-at.bofh.it> (permalink)
References	(1 earlier) <rlHiy-6xv-21@gated-at.bofh.it> <rlHLA-6M8-11@gated-at.bofh.it> <rlIxY-7r6-39@gated-at.bofh.it> <rlIHD-7v9-1@gated-at.bofh.it> <rlJDH-8aP-3@gated-at.bofh.it>
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Hello, Waiman.

On Fri, Apr 08, 2016 at 02:45:38PM -0400, Waiman Long wrote:
> The percpu_stats construct allows minimal overhead in maintaining statistics
> counts. The percpu_counter construct, on the other hand, has a higher
> performance overhead and a bit more complex to set up and tear down when

If you're referring to the preemption on/off, as I wrote before, we'll
probably be able to improve that with this_cpu_add_return so that the
only extra overhead is an easily predictable branch which is extremely
cheap.  It's better to improve common constructs anyway.

> more than one statistics counts are needed. In fact, my first draft of the

And yeah, it can be cumbersome to set up and tear down multiple
percpu_counters.  If there are enough consumers, we can extend
percpu_counter to handle multiple counters, right?

Thanks.

-- 
tejun

Thread

[PATCH v2 0/4] ext4: Improve parallel I/O performance on NVDIMM Waiman Long <Waiman.Long@hpe.com> - 2016-04-08 18:20 +0200
  [PATCH v2 3/4] ext4: Pass in DIO_SKIP_DIO_COUNT flag if inode_dio_begin() called Waiman Long <Waiman.Long@hpe.com> - 2016-04-08 18:20 +0200
  [PATCH v2 2/4] percpu_stats: Enable 64-bit counts in 32-bit architectures Waiman Long <Waiman.Long@hpe.com> - 2016-04-08 18:20 +0200
    Re: [PATCH v2 2/4] percpu_stats: Enable 64-bit counts in 32-bit  architectures Tejun Heo <tj@kernel.org> - 2016-04-08 18:50 +0200
      Re: [PATCH v2 2/4] percpu_stats: Enable 64-bit counts in 32-bit architectures Waiman Long <waiman.long@hpe.com> - 2016-04-08 19:40 +0200
        Re: [PATCH v2 2/4] percpu_stats: Enable 64-bit counts in 32-bit  architectures Tejun Heo <tj@kernel.org> - 2016-04-08 19:50 +0200
          Re: [PATCH v2 2/4] percpu_stats: Enable 64-bit counts in 32-bit architectures Waiman Long <waiman.long@hpe.com> - 2016-04-08 20:50 +0200
            Re: [PATCH v2 2/4] percpu_stats: Enable 64-bit counts in 32-bit  architectures Tejun Heo <tj@kernel.org> - 2016-04-12 00:20 +0200
              Re: [PATCH v2 2/4] percpu_stats: Enable 64-bit counts in 32-bit architectures Waiman Long <waiman.long@hpe.com> - 2016-04-12 20:20 +0200
  [PATCH v2 1/4] percpu_stats: Simple per-cpu statistics count helper functions Waiman Long <Waiman.Long@hpe.com> - 2016-04-08 18:20 +0200
    Re: [PATCH v2 1/4] percpu_stats: Simple per-cpu statistics count  helper functions kbuild test robot <lkp@intel.com> - 2016-04-08 18:50 +0200
    Re: [PATCH v2 1/4] percpu_stats: Simple per-cpu statistics count  helper functions kbuild test robot <lkp@intel.com> - 2016-04-08 19:50 +0200

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