DragonFly BSD
DragonFly kernel List (threaded) for 2010-05
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Re: VM idle page zeroing

From: Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxx>
Date: Sun, 16 May 2010 17:20:49 -0700 (PDT)

:Any particular reason for moving the thread to the last cpu?

    No, It is just an experiment. There is no need to put it on cpu 0
    on a SMP system since numerous dedicated threads already run on cpu 0.
    It can't hurt, anyhow.

:Something that occured to me - right now, we have a thread that wakes up
:every 1/10th of a second, checks if there are pages to zero. At long
:stretches of idle time, we just end up waking and sleeping a whole lot.
:Instead, perhaps, when vm_page_zero_check() sees that we hit ZIDLE_HIGH we
:should perhaps sleep for a lot longer and drop down to the usual rate when
:we hit ZIDLE_LOW?
:-- vs

    Yes and no.  Yes it is probably worth doing as sleep states become
    more advanced.  But on the flip side the actual cpu use is miniscule,
    less than 0.01%.  Essentially 10uS once every 1/10 second and with
    no locking requirements in the no-work case.


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