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    SubjectRe: [PATCH 01/13] writeback: IO-less balance_dirty_pages()
    On Thu, 2010-11-18 at 21:26 +0800, Wu Fengguang wrote:
    > On Thu, Nov 18, 2010 at 09:04:34PM +0800, Peter Zijlstra wrote:
    > > On Wed, 2010-11-17 at 12:27 +0800, Wu Fengguang wrote:
    > > > - avoid useless (eg. zero pause time) balance_dirty_pages() calls
    > > > - avoid too small pause time (less than 10ms, which burns CPU power)
    > > > - avoid too large pause time (more than 100ms, which hurts responsiveness)
    > > > - avoid big fluctuations of pause times
    > >
    > > If you feel like playing with sub-jiffies timeouts (a way to avoid that
    > > HZ=>100 assumption), the below (totally untested) patch might be of
    > > help..
    > Assuming there are HZ=10 users.
    > - when choosing such a coarse granularity, do they really care about
    > responsiveness? :)

    No of course not, they usually care about booting their system,.. I've
    been told booting Linux on a 10Mhz FPGA is 'fun' :-)

    > - will the use of hrtimer add a little code size and/or runtime
    > overheads, and hence hurt the majority HZ=100 users?

    Yes it will add code and runtime overhead, but it would allow you to
    have 1ms timeouts even on a HZ=100 system, as opposed to a 10ms minimum.

    Anyway, I'm not saying you should do it, I just wondered if we had the
    API, saw we didn't and thought it might be nice to offer it if desired.

     \ /
      Last update: 2010-11-18 14:43    [W:0.025 / U:7.020 seconds]
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