2.4.26 and MPC885 context switching time
> Therefore i wonder, if there are any known problems with the > MMU on 8xx and 2.4.2x which might explain that? > I did some work on an 885 with Linux 2.4.22. I found that when the processor was running at 100MHz or higher Linux would die when decompressing the ramdisk. Below 100MHz it would run fine. I came up with a hacky fix because I mis-read an errata notice. What I did was set the ICTRL register to 0x0001, this fixed the problem. Basically all this does is slow the processor down considerable. The Linux you have may be doing the same thing. This could explain the performance hit you are seeing.
2.4.26 and MPC885 context switching time
In message <187119B8-515D-4903-AAB5-05BF80215A4D at aimsys.nl> you wrote: > I did once ran lmbench on a proprietry 850 based board running at > 62/31 Mhz using 1 16-bit dram: > > Context switching - times in microseconds - smaller is better > - > Host OS 2p/0K 2p/16K 2p/64K 8p/16K 8p/64K 16p/16K 16p/ > 64K > ctxsw ctxsw ctxsw ctxsw ctxsw ctxsw > ctxsw > - - - -- -- -- -- --- > --- > testLinux 2.4.25- 259.2 234.2 302.6 304.7 > > This is ~ 3x faster then your 100Mhz 885... I just ran lmbench on a MPC866 system (CPU at 132 MHz, bus at 66 MHz): Context switching - times in microseconds - smaller is better - Host OS 2p/0K 2p/16K 2p/64K 8p/16K 8p/64K 16p/16K 16p/64K ctxsw ctxsw ctxsw ctxsw ctxsw ctxsw ctxsw - - -- -- -- -- -- --- --- tqm8xx Linux 2.4.25 5.4500 27.5 30.3 39.0 36.037.733.5 There is definitely something wrong with Peter's measurements. Best regards, Wolfgang Denk -- Software Engineering: Embedded and Realtime Systems, Embedded Linux Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de Quantum particles: The dreams that stuff is made of.
2.4.26 and MPC885 context switching time
I did once ran lmbench on a proprietry 850 based board running at 62/31 Mhz using 1 16-bit dram: Context switching - times in microseconds - smaller is better - Host OS 2p/0K 2p/16K 2p/64K 8p/16K 8p/64K 16p/16K 16p/ 64K ctxsw ctxsw ctxsw ctxsw ctxsw ctxsw ctxsw - - - -- -- -- -- --- --- testLinux 2.4.25- 259.2 234.2 302.6 304.7 This is ~ 3x faster then your 100Mhz 885... Jaap-Jan On 15-jun-2005, at 16:55, Schaefer-Hutter, Peter wrote: > Hi all, > > i'm evaluating IPC on the MPC885ADS and discovered > that the context switching times seem to be quite > disappointing (up to 1ms). As we need to do a lot > of IPC later on, i'm interested bringing the time > down. > > Therefore i wonder, if there are any known problems > with the MMU on 8xx and 2.4.2x which might explain > that? > > Or is this the expected context switching time for > CPU @ 100 MHz (RAM @ 50 MHz)? Suggestions for a > benchmark program? > > Thanks! > > Peter > ___ > Linuxppc-embedded mailing list > Linuxppc-embedded at ozlabs.org > https://ozlabs.org/mailman/listinfo/linuxppc-embedded > > > J.G.J. Boor Anton Philipsweg 1 Software Engineer 1223 KZ Hilversum AimSys bv tel. +31 35 689 1941 Postbus 2194, 1200 CD Hilversum jjboor at aimsys dot nl
2.4.26 and MPC885 context switching time
On Jun 15, 2005, at 11:43 AM, Schaefer-Hutter, Peter wrote: > I basically used the two programs from > http://www.ibm.com/developerworks/linux/library/l-rt9/ That's a fine test, if you run it on various systems and compare the _relative_ results. There is more than context switching going on here. there aren't any MMU "problems" with the 8xx, it's likely to be the most efficient implementation of all systems that use software to support the MMU. The processor in general is very sensitive to many system architecture decisions, especially the system bus and DRAM configuration. Make certain you really understand what you have configured and how the tests you run are affected by that. Thanks. -- Dan
2.4.26 and MPC885 context switching time
> Maybe it would help if you gave more detail about how > you are measuring these times in your system. I basically used the two programs from http://www.ibm.com/developerworks/linux/library/l-rt9/ since running lmbench is currently not an option; however, i'm looking into creating a nfs filesystem that has enough stuff in it to run lmbench. Regards, Peter
AW: 2.4.26 and MPC885 context switching time
Hi Peter, linuxppc-embedded-bounces at ozlabs.org wrote on : > i'm evaluating IPC on the MPC885ADS and discovered > that the context switching times seem to be quite > disappointing (up to 1ms). As we need to do a lot .. > Or is this the expected context switching time for > CPU @ 100 MHz (RAM @ 50 MHz)? Suggestions for a > benchmark program? Denx has done some detailed performance measurements (including context switching). You could find the report here: http://www.denx.de/twiki/bin/view/Know/Linux24vs26. Hope that is of some help. Regards, Martin
2.4.26 and MPC885 context switching time
Hi all, i'm evaluating IPC on the MPC885ADS and discovered that the context switching times seem to be quite disappointing (up to 1ms). As we need to do a lot of IPC later on, i'm interested bringing the time down. Therefore i wonder, if there are any known problems with the MMU on 8xx and 2.4.2x which might explain that? Or is this the expected context switching time for CPU @ 100 MHz (RAM @ 50 MHz)? Suggestions for a benchmark program? Thanks! Peter
2.4.26 and MPC885 context switching time
Question embedded below.. > -Original Message- > From: linuxppc-embedded-bounces at ozlabs.org > [mailto:linuxppc-embedded-bounces at ozlabs.org] On Behalf Of > Martin Krause > Sent: June 15, 2005 11:12 AM > To: Schaefer-Hutter, Peter > Cc: linuxppc-embedded at ozlabs.org > Subject: AW: 2.4.26 and MPC885 context switching time > > > Hi Peter, > > linuxppc-embedded-bounces at ozlabs.org wrote on : > > i'm evaluating IPC on the MPC885ADS and discovered > > that the context switching times seem to be quite > disappointing (up to > > 1ms). As we need to do a lot > .. > > Or is this the expected context switching time for > > CPU @ 100 MHz (RAM @ 50 MHz)? Suggestions for a > > benchmark program? > > Denx has done some detailed performance measurements > (including context switching). You could find the report > here: http://www.denx.de/twiki/bin/view/Know/Linux24vs26. > Hope that is of some help. > Has anything changed with 2.6 in the last 12 months that would alter the conclusions presented in this article? A. > Regards, > Martin > ___ > Linuxppc-embedded mailing list > Linuxppc-embedded at ozlabs.org > https://ozlabs.org/mailman/listinfo/linuxppc-> embedded > > -- next part -- An HTML attachment was scrubbed... URL: http://ozlabs.org/pipermail/linuxppc-embedded/attachments/20050615/e5db23a1/attachment.htm
2.4.26 and MPC885 context switching time
>Hi all, > >i'm evaluating IPC on the MPC885ADS and discovered >that the context switching times seem to be quite >disappointing (up to 1ms). As we need to do a lot >of IPC later on, i'm interested bringing the time >down. > >Therefore i wonder, if there are any known problems >with the MMU on 8xx and 2.4.2x which might explain >that? Maybe it would help if you gave more detail about how you are measuring these times in your system. I'm interested to know the answer to this myself! Mark Chambers
