Date: Tue, 26 Jan 1999 17:40:13 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Dan Root <dar@thekeep.org> Cc: freebsd-current@FreeBSD.ORG Subject: Re: Memory usage weirdness Message-ID: <199901270140.RAA27083@apollo.backplane.com> References: <19990126183430.A61727@thekeep.org>
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:
:What would cause more memory to be considered in the active state than
:could be accounted for by running processes?
:
:My main machine (running -current as of the afternoon of Jan 25) has
:somewhere between 80 and 100 megs of memory listed as used via ps and top
:(which, I presume doesn't take in to account shared executable pages, but
:does include the 16 megs the X server is mapping on the video card), yet
:both top and vmstat show over 170 megs worth of memory being active.
:
:Furthermore, if I kill off my X session and associated processes, active
:memory usage doesn't decrease, even after 5 or more minutes. According to
:...
There are two different things here:
(1) AVM ( Active Virtual Memory ) and ARM ( Active Real Memory ).
These might include device mmaps that are not considered real memory
by the paging subsystem ( though I believe I've fixed the AVM thingy
where X would mmap /dev/mem and AVM would become insane ).
(2) VM Paging queue statistics
wired, active, inactive, cache, free.
The VM system does not bother moving things from active to inactive
unless there is some stress on the memory subsystem. If you are
just sitting idle, I wouldn't expect to see active pages moved to
inactive.
X consists of quite a few direct maps of code, and less in the way of
BSS data. So when you exit the X session, only the BSS data, which has
no backing store on exit, will have been returned ( active->free queue ).
The mmap'd code, which is vnode-backed, just stays active until something
stresses the memory subsystem.
-Matt
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