Re: 2.3.12 - klogd 100% CPU && Bogus Buffer memory count

Thomas Zimmerman (qubes@aa.net)
Sat, 07 Aug 1999 02:55:15 -0700

Mofeed Shahin wrote:
>
> Well, I don't have the CD that it did it with anymore but when I did it
> yesterday this showed up in the logs :
>
> Aug 6 03:29:12 tt2 kernel: attempt to access beyond end of device
> Aug 6 03:29:12 tt2 kernel: 0b:00: rw=0, want=532574, limit=532572
>
> Chuck I will try to get the CD back again tomorrow or Monday, and see if
> it does it again.
>
> Cheers Mof.
>
> On Fri, 6 Aug 1999, Chuck Lever wrote:
>
> > mofeed-
> >
> > there's a race somewhere that's causing shrink_mmap to deduct too much
> > from buffermem, making it go negative. i don't think that it's specific
> > to a particular driver. i haven't been able to simply and consistently
> > reproduce the race -- maybe you could come up with some way to do this?
> > is it specific to how much data you copied, for instance?
> >
> > On Fri, 6 Aug 1999, Mofeed Shahin wrote:
> > > First off I will explain what I was doing that caused the problem.
> > > I was copying a whole CD to the hard-drive. They are both scsi AIC7xxx.
> > >
> > > While I was copying I noticed Xosview not looking too healthy so I ran top
> > > and noticed that the amount of buffer memory was obviously wrong.
> > >
> > > here is the vmstat output :
> > >
> > > :vmstat
> > > procs memory swap io system cpu
> > > r b w swpd free buff cache si so bi bo in cs us sy id
> > > 1 0 0 744 2908 4193304 205452 0 0 2 4 52 14 47 0 53
> > > ^^^^^^^
> > > Notice the 4.1 GIG of buffer memory.
> > >
> > > Also half way through the copy klogd started using up all the CPU time on
> > > one of the processors.
> > > Even after the copy had finished klogd was still using up large amounts of
> > > CPU (100%).

I also noticed bogus buffer memory reported as used. I was using Grip to
rip and encode several CD here at home. I have only noticed this after
the fact (when I fire up top to make sure everything is still working
smoothly.) Here is a snipit from the logs:
Aug 6 23:42:58 darklands kernel: attempt to access beyond end of device
Aug 6 23:42:58 darklands kernel: 03:05: rw=0, want=270178616,
limit=2048256
Aug 6 23:43:03 darklands kernel: attempt to access beyond end of device
Aug 6 23:43:03 darklands kernel: 03:05: rw=0, want=270178616,
limit=2048256
Aug 6 23:43:03 darklands kernel: attempt to access beyond end of device
Aug 6 23:43:03 darklands kernel: 03:05: rw=0, want=270178616,
limit=2048256
Aug 6 23:43:03 darklands kernel: attempt to access beyond end of device
Aug 6 23:43:03 darklands kernel: 03:05: rw=0, want=270178616,
limit=2048256

And the output of free:
[qubes@darklands qubes]$ free
total used free shared buffers
cached
Mem: 127708 124064 3644 55732 4189992
74092
-/+ buffers/cache: 54284 73424
Swap: 136512 6852 129660

Qubes

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