Unfreed kernel buffers (fsck and 2.3.99-pre*)

From: Craig Kulesa (ckulesa@loke.as.arizona.edu)
Date: Sat Mar 18 2000 - 04:13:16 EST


Summary:
       After running fsck, a large block of kernel "buffer"
       memory (seen in /proc/meminfo or 'free') is allocated in 2.3.99.
       This large block of RAM is _not_ freed under memory stress, and
       induces very heavy paging. A reboot seems necessary to recover.

System has 32 MB, i586, SCSI disk on VLB. Kernel config is available here:
http://loke.as.arizona.edu/~ckulesa/syrinx-config

This system performed an fsck (version 1.15) on the root filesystem at
boot time. Afterwards, a large block of RAM was allocated as kernel
buffers:

             total used free shared buffers cached
Mem: 30364 29564 800 0 12416 8084
-/+ buffers/cache: 9064 21300
Swap: 32764 328 32436

After loading Netscape, gimp, and emacs -- putting the system under
substantial memory load, this block of buffer memory _was never
deallocated_, causing intensive swapping and a very high system load:

             total used free shared buffers cached
Mem: 30364 29480 884 0 12176 8188
-/+ buffers/cache: 9116 21248
Swap: 32764 17400 15364

This behavior after fsck is reliably reproducible on several machines
that were tested, running 2.3.99-pre1 or pre2-3. System performance was
only recovered by rebooting.

Any ideas? Patches? :)

Many thanks,

Craig Kulesa
ckulesa@as.arizona.edu

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