severe slowdown with 2.4 series w/heavy disk access

severe slowdown with 2.4 series w/heavy disk access

Post by Paul Bole » Fri, 28 Dec 2001 01:40:07




> >              total       used       free     shared    buffers
> > cached
> > Mem:        417472     412192       5280          0      20632
> > 315680

> Thyose values dont show any problems. In fact your machine seems to think it
> had a ton of free memory to waste and has let it fill up with stuff that has
> been accessed - just on the chance that it may be reused.

> It hasn't even felt enough memory pressure to start swapping. When you
> say it "becomes slow", what precisely becomes slow ?

When this happens in X, the mouse drags and skips, any processes running
(like tar/gzip. ls in an empty dir takes about 10 seconds) slow down,
and it happens usually for about 10sec-2min, often for no apparent
reason.  The big decompression was just a way I can easily duplicate
it.  Oddly enough though, according to top, it caches all that memory at
once, and my free goes down to 5 megs, with the system*/slow to
respond, for 10sec-2min.  Even typing in the console has delay before
the characters appear, and according to top, tar and gz are both using
under 1% cpu while this happens, and about 50% of the cpu is in use by
the system (not by any processes that I can see.  kupdated goes up to
about 0.3% during this)

Quote:

> Also what disks do you have and how are they set up ?
> -

/dev/hdb3 on / type ext2 (rw)
/dev/hdb4 on /home type ext2 (rw)
/dev/hda1 on /dos/c type vfat (rw)
/dev/hdb1 on /dos/d type vfat (rw)
none on /dev/pts type devpts (rw,gid=5,mode=620)
none on /proc type proc (rw)

and my swap is /dev/hdb2
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1. severe slowdown with 2.4 series w/heavy disk access (revisited)

Hi'all,

Anyone remember this thread:

   "severe slowdown with 2.4 series w/heavy disk access"

   http://hypermail.spyroid.com/linux-kernel/archived/2001/week52/0266.html

It describes the tendency of 2.4 series kernels to slowdown under I/O load.
Well, that problem still seems to be alive and kicking. And no, it is not
related to reiserfs as I previously suggested in this thread:

   "Abysmal interactive performance on 2.4.linus", archived here:

   http://www.uwsg.iu.edu/hypermail/linux/kernel/0111.1/0911.html

I removed the last reiserfs partition quite some time ago, currently running
mostly ext3 with ext2 root fs.

The systems use IDE disks, I don't have any SCSI-systems handy to test whether
this might be IDE-only (anyone?). Currently running 2.4.18 (with preempt and
lowlatency, but the problems are NOT related to those patches as they also hit
unpatched kernels) on SMP (Abit BP-6 yeah yeah I know but it does not seem to
be specific to the BP-6).

Does anyone else see these problems? Specifically, does anyone with a
SCSI-based system see this happening? Also, does anyone who uses only ext2 (no
ext3 or reiserfs, let alone jfs/xfs or any other journaling fs) see this?

Cheers//Frank

 [ BTW: I'm moving to Sweden, and am looking for a project/job in V?stra
   G?taland, preferrably G?teborg... Anyone know anything interesting? ]
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