Re: Problems reclaiming VM cache = XFree86 startup annoyance

From: Matthew Dillon (dillon_at_apollo.backplane.com)
Date: 12/25/03

  • Next message: Shawn K. Quinn: "Very weird problem with dc driver" 
    Date: Wed, 24 Dec 2003 23:10:08 -0800 (PST)
To: Paul Mather <paul@gromit.dlib.vt.edu>

    :I'm not sure what is overloading the disk other than the large amounts
    :of paging that are initiated the moment I invoke "startx". The last
    :time I did this, I looked at the disk activity beforehand via "systat
    :-vm 1". The disks were basically idle (all < 0.05 MB/s). As soon as
    :I executed "startx" the swap volume became very active (90--96% busy;
    :3--7 MB/sec) and the "SWAP PAGER" out column steadily showed paging
    :activity (nothing on the "in" column). (The 4 KB/t was a tell-tale
    :sign the system was doing nothing but paging.)
    :
    :I guess my question is this: why so much paging? If, as someone else
    :has mentioned, "Cache" and "Free" pages are both "free" (i.e.,
    :allocable memory), with the subtle distinction being that "Cache"
    :pages used to hold disk blocks now discarded, then why not allocate
    :what is needed from them? As I stated in my original thread, all the
    :"Inactive" memory seems to get dumped over to "Cache" when I run
    :"startx", and there's usually almost about 400 MB of it when this
    :happens.
    :...
    :Cheers,
    :
    :Paul.

       If it could, it would... my guess is that your box is using a shared
       memory video buffer and X is allocating a large swath of
       contiguous physical memory to accomodate it, which would force it to
       pageout any preexisting dirty data using that memory. That's all I can
       think of.

                                            -Matt
                                            Matthew Dillon
                                            <dillon@backplane.com>
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  • Next message: Shawn K. Quinn: "Very weird problem with dc driver"

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