I (read: my company) am working on a semi-embedded system (no swap, booting
onto a ramdisk), and I recently changed linux kernels from 2.4.9 to 2.4.19.
Nearly everything works fine, except that whenever I read a file, it
allocates 4k of memory (cat /proc/meminfo reports 4k less memory, and
/proc/slabinfo reports that buffer_head increases by 4k, but those are the
only changes). I found a thread from back in July or so on LKML where
somebody had a similar problem on 2.4.19-rc3, and Rik said that this was
normal, and the vm would release this memory under pressure, except when I
start a bunch of processes to use up memory and repeatedly cat
/proc/meminfo, the OOM killer is eventually triggered.
I'm running 2.4.19 with both the low-latency and kernel preemption patches
applied (though I recompiled the kernel with those disabled and the problem
still occurred), as well as a few changes of our own (though none of those
seem to touch the filesystem/vm layers). It's a powerpc chip with 64 megs
of ram (roughly 28 of which are free after we load the kernel/ramdisk and
all our apps). I tried to reproduce the problem on my PC (booted up without
X, specified mem=8M on command line, and turned off swap), which is also
2.4.19 and also has the kernel preemption and low-latency patches applied,
but is not booting from a ramdisk and is, obviously, a different
architecture, and it did allocate 4k blocks for a while, but then stopped
(or, more accurately, it would allocate 4k and then the next time I did a
cat /proc/meminfo it would be back to its original value).
So I guess my question is:
1) What is eating up memory and not allowing it to be freed, and
2) Why does it allocate 4k of memory every single time I access a file,
anyway?
Any help would be greatly appreciated.
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This archive was generated by hypermail 2b29 : Mon Oct 07 2002 - 22:01:01 EST