Problems reclaiming VM cache = XFree86 startup annoyance

Matthew Dillon dillon at
Wed Dec 24 23:10:10 PST 2003

: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

   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.

					Matthew Dillon 
					<dillon at>

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