RE: kupdated high load with heavy disk I/O

["Rechenberg, Andrew" <ARechenberg@shermanfinancialgroup.com>]

Ken,

The 2.4.15pre7 kernel seems to have fixed my issue with kupdated and 4GB
RAM.  We did some testing over the weekend and the box was still interactive
with a load of 7+.  There still seems to be a lot of swapping going on
though.  I've read from previous threads that 2.4 uses swap more readily
than 2.2 did, but should it use 10% of my swap and have almost 8MB
SwapCached?

Here are some numbers for example:

[root@mybox ~]# cat /proc/meminfo
        total:    used:    free:  shared: buffers:  cached:
Mem:  4092899328 4082126848 10772480        0 12406784 3672317952
Swap: 542826496 57561088 485265408
MemTotal:      3996972 kB
MemFree:         10520 kB
MemShared:           0 kB
Buffers:         12116 kB
Cached:        3578108 kB
SwapCached:       8140 kB
Active:        2964668 kB
Inactive:       877168 kB
HighTotal:     3145720 kB
HighFree:         2084 kB
LowTotal:       851252 kB
LowFree:          8436 kB
SwapTotal:      530104 kB
SwapFree:       473892 kB
[root@mybox ~]# free
             total       used       free     shared    buffers     cached
Mem:       3996972    3986640      10332          0      12156    3577900
-/+ buffers/cache:     396584    3600388
Swap:       530104      56340     473764


The above question is more for my personal knowledge, but I would like to
know.

Thanks again for your help.

Regards,
Andy.



-----Original Message-----
From: Ken Brownfield [mailto:brownfld@irridia.com]
Sent: Wednesday, November 21, 2001 12:07 PM
To: Rechenberg, Andrew
Subject: Re: kupdated high load with heavy disk I/O


Yeah, the kswapd/kupdated issue was patched in -pre7:

	 - me: modified Andrea VM page allocator tuning

-pre8 came out after I mailed you. ;-)  So unless it's mentioned it
should stay in the kernel.

Of course, it's important to give it a try soon if you can, just to make
sure that it _does_ solve your specific problem.  Especially before the
kernel is handed off to Marcelo.

Thx,
-- 
Ken.


On Wed, Nov 21, 2001 at 11:09:17AM -0500, Rechenberg, Andrew wrote:
| Ken,
| 
| Thanks for the reply.  I would assume then that any future 15-pre kernel
| would have the same fix?  I ask because pre8 is now the current 15-pre.
| 
| Thanks,
| Andy.
| 
| -----Original Message-----
| From: Ken Brownfield [mailto:brownfld@irridia.com]
| Sent: Tuesday, November 20, 2001 6:09 PM
| To: Rechenberg, Andrew
| Subject: Re: kupdated high load with heavy disk I/O
| 
| 
| Be sure to tru 2.4.15-pre7 which should fix your problem.
| -- 
| Ken.
| brownfld@irridia.com
| 
| On Tue, Nov 20, 2001 at 05:58:44PM -0500, Rechenberg, Andrew wrote:
| | I have to find time to down the box because it's production, but as soon
| as
| | I do I'll post the numbers here.
| | 
| | Thanks for your help.	
| | 
| | Regards,
| | Andy.
| | 
| | 
| | > Could you please guys try to reproduce the problem with kernel
profiling
| | > turned on and send us the output of readprofile? 
| | 
| | > This way we can know which function is using more CPU time, thus we
can
| | > identify the problem. 
| | 
| | 
| | On Wed, 14 Nov 2001, John McCutchan wrote:
| | 
| | > Hi,
| | > 
| | > I also have the exact same behaviour when running mkisofs. During the 
| | > creation of the ISO the interactive feel is sluggish and after mkisofs
| | > is complete the box is sluggish and appears to lock up. During
| | > this sluggish period there is alot of disk activity. This is under
| | > 2.4.14
| | > 
| | > John
| | > On Wed, Nov 14, 2001 at 06:01:23PM -0500, Rechenberg, Andrew wrote:
| | > > Hello,
| | > > 
| | > > I have read some previous threads about kupdated consuming 99% of
CPU
| | under
| | > > intense disk I/O in kernel 2.4.x on the archives of linux-kernel
| (April
| | > > 2001), and some issues about I/O problems on linux-mm, but have yet
to
| | find
| | > > any suggestions or fixes.  I am currently experiencing the same
issue
| | and
| | > > was wondering if anyone has any thoughts or suggestions on the
issue.
| I
| | am
| | > > not subscribed to the list so would you please CC: me directly on
any
| | > > responses?  I can also check out the archives at theaimsgroup.com if
a
| | CC:
| | > > would not be appropriate.  Thank you.
| | > > 
| | > > The issue that I am having is that when there is a heavy amount a
disk
| | I/O,
| | > > the box becomes slightly unresponsive and kupdated is using 99.9% in
| | 'top.'
| | > > Sometimes the box appears to totally lock up.  If one waits several
| | seconds
| | > > to a couple of minutes the system appears to 'unlock' and runs
| | sluggishly
| | > > for a while.  This cycle will repeat itself until the I/O subsides.
| The
| | > > memory usage goes up to the full capacity of the box and then about
| 10MB
| | of
| | > > swap is used while this problem is occurring.  Memory and swap does
| not
| | get
| | > > relinquished afer the incident.
| | > > 
| | > > The issue appears in kernel 2.4.14 compiled directly from source
from
| | > > kernel.org with no patches.  These problems manifest themselves with
| | only
| | > > one user doing heavy disk I/O.  The normal user load on the box can
| run
| | > > between 350-450 users so this behavior would be unacceptable because
| the
| | > > application that is being run is interactive.  With 450 users, and
the
| | same
| | > > process running on a 2.2.20 kernel the performance of the box is
| great,
| | with
| | > > only a very slightly noticeable slow down.
| | > > 
| | > > I am running the Informix database UniVerse version 9.6.2.4 on a 4
| | processor
| | > > 700MHz Xeon Dell PowerEdge 6400.  The disk subsystem is controlled
by
| a
| | PERC
| | > > 2/DC RAID card with 128MB on-board cache (megaraid driver compiled
| | directly
| | > > in to the kernel).  Data array is on 5 36GB 10K Ultra160 disks in a
| | RAID5
| | > > configuration.  The box has 4GB RAM, but is only using 2GB due to
the
| | move
| | > > back to the 2.2 kernel.  The only kernel paramters that have been
| | modified
| | > > are in /proc/sys/kernel/sem.  All filesystems are ext2.
| | > > 
| | > > If you need any more detailed info, please let me know.  Any help on
| | this
| | > > problem would be immensely appreciated.  Thank you in advance.
| | > > 
| | > > Regards,
| | > > Andrew Rechenberg
| | > > Network Team, Sherman Financial Group
| | > > arechenberg@shermanfinancialgroup.com
| | > > 
| | > > --
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| | > > see: http://www.linux-mm.org/
| | > > 
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