Memory + FileSystem issue (2.3.99-preX)?

From: Terry Katz (katz@advanced.org)
Date: Sat Apr 22 2000 - 10:47:27 EST


We noticed something weird that happens between the filesystem and memory
usage under the 2.3.99 series (we started using them at pre3, and are now at
pre6-5)..

When writing a file (in this case, a large test file), as the file gets
larger, the amount of memory gets larger. I tested this by using dd to
create up to a 300 meg file, and watched the memory usage .. As the file
size grew, so did the mem usage.. I cancelled out of the dd when the memory
was over 95% (over 200meg) utilized and waited a bit (bout 30 seconds) ..
and the amount of memory used stayed at over 95%... if I deleted the file
then the usage immediately dropped to under 50meg used...

We initially noticed the problem when downloading (via ftp) large log files
(between 300 meg and a few gig) to the box .. That machine has about 1 gig
of memory, and as files were downloading the usage just grew .. ie, if we
grabbed a 300 meg file, we then had 300 meg of used ram, the next file of
400 meg grew the usage up to about 700, etc... until all ram was used the
system became extremely slow .. if we waited a long while (after cancelling
the download) the system eventually became responsive again .. if we managed
to delete the files immediately .. then it became responsive immediately...

Known issue?

The box I ran the dd test on, is a home-built dual-600, 256meg ram, ide,
tyan motherboard .. the machine we did the download with at the office is a
Dell PowerEdge 4400, p3-600, with 1gig of ram, and ami megaraid controller..

-Terry

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