On Mon, Feb 06, 2006, Andrew Morton wrote:
> Mark Lord <[email protected]> wrote:
> >
> > A simple test I do for this:
> >
> > $ mkdir t
> > $ cp /usr/src/*.bz2 t (about 400-500MB worth of kernel tar files)
> >
> > In another window, I do this:
> >
> > $ while (sleep 1); do echo -n "`date`: "; grep Dirty /proc/meminfo; done
> >
> > And then watch the count get large, but take virtually forever
> > to count back down to a "safe" value.
> >
> > Typing "sync" causes all the Dirty pages to immediately be flushed to disk,
> > as expected.
>
> I've never seen that happen and I don't recall seeing any other reports of
> it, so your machine must be doing something peculiar. I think it can
> happen if, say, an inode gets itself onto the wrong inode list, or
> incorrectly gets its dirty flag cleared.
>
> Are you using any unusual mount options, or unusual combinations of
> filesystems, or anything like that?
I've been seeing something like this for some time, but kept
silent as I'm forced to use vmware on my Thinkpad T42p (1G RAM,
but CONFIG_NOHIGHMEM=y).
Sometimes 'sync' takes serveral seconds, even when the machine
had been idle for >15mins. I don't have laptop mode enabled.
so far I've not found a deterinistic way to reproduce this behaviour.
Anyway, I temporarily deinstalled vmware (deleted the kernel
modules and rebooted; kernel is still tainted because of madwifi
if that matters).
The behaviour I see with vmware (long 'sync' time) doesn't seem
to happen without it so far, but:
Now copying a 700MB file makes "Dirty" go up to 350MB. It then
slowly decreases to 325MB and stays there. However:
$ time sync
real 0m0.326s
user 0m0.000s
sys 0m0.280s
and output from the dirty monitor one-liner:
Mon Feb 13 14:31:43 CET 2006: Dirty: 325916 kB
Mon Feb 13 14:31:44 CET 2006: Dirty: 325916 kB
Mon Feb 13 14:31:45 CET 2006: Dirty: 4 kB
Mon Feb 13 14:31:46 CET 2006: Dirty: 8 kB
Clearly my notebook's hdd isn't that fast. ;-/
What does "Dirty" in /proc/meminfo really mean?
Kernel is 2.6.15, fs is ext3, .config etc. on request.
Johannes
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