IBM just donated a dual socket 10 cores per socket power-8 machine to the department. I thought I would run a quick test and was amused to see this:
[hyatt@blueblaze crafty]$ ./crafty
unable to open book file [./book.bin].
book is disabled
unable to open book file [./books.bin].
Crafty v25.1
machine has 160 processors <---------------
White(1):
Turns out the power 8 has 8 hyper threaded cores per physical core. 160 indeed. Only downside here is that it is about 20% slower per core than our Intel 2660 20 core box. I am looking into spin locks so I can run a 20 core test to see how it works, and to even try 40 and beyond to see if their hyper threading offers anything beyond Intel...
Interesting machine
Moderators: hgm, Rebel, chrisw
-
- Posts: 3196
- Joined: Fri May 26, 2006 3:00 am
- Location: WY, USA
- Full name: Michael Sherwin
Re: Interesting machine
Sounds like a very economical platform to develop an application that requires a huge number of threads.
If you are on a sidewalk and the covid goes beep beep
Just step aside or you might have a bit of heat
Covid covid runs through the town all day
Can the people ever change their ways
Sherwin the covid's after you
Sherwin if it catches you you're through
Just step aside or you might have a bit of heat
Covid covid runs through the town all day
Can the people ever change their ways
Sherwin the covid's after you
Sherwin if it catches you you're through
-
- Posts: 20943
- Joined: Mon Feb 27, 2006 7:30 pm
- Location: Birmingham, AL
Re: Interesting machine
Only question is, how effective is that high level of hyper threading? I have not yet had time to figure out a good lock mechanism (spin lock) as I have a bunch of details to handle as I finalize my retirement paperwork and such.Michael Sherwin wrote:Sounds like a very economical platform to develop an application that requires a huge number of threads.
-
- Posts: 5228
- Joined: Thu Mar 09, 2006 9:40 am
- Full name: Vincent Lejeune
Re: Interesting machine
The target of IBM is probably not 1 application multi-threaded but many different applications running on 1 core.bob wrote:Only question is, how effective is that high level of hyper threading? I have not yet had time to figure out a good lock mechanism (spin lock) as I have a bunch of details to handle as I finalize my retirement paperwork and such.Michael Sherwin wrote:Sounds like a very economical platform to develop an application that requires a huge number of threads.
-
- Posts: 20943
- Joined: Mon Feb 27, 2006 7:30 pm
- Location: Birmingham, AL
Re: Interesting machine
Yes. Hyper threading has the same issue it has always had. Got the thing working with a spin lock for power 8. So far, "OK". Speedup comparable to the 20 core 2660 box, except the power 8 at 3.4ghz is about 20% slower than the 2660 at 2.9ghz...Vinvin wrote:The target of IBM is probably not 1 application multi-threaded but many different applications running on 1 core.bob wrote:Only question is, how effective is that high level of hyper threading? I have not yet had time to figure out a good lock mechanism (spin lock) as I have a bunch of details to handle as I finalize my retirement paperwork and such.Michael Sherwin wrote:Sounds like a very economical platform to develop an application that requires a huge number of threads.
One interesting thing is this machine has 1 TB of DRAM. Have not run on a single box with this much memory previously:
[hyatt@blueblaze crafty]$ more /proc/meminfo
MemTotal: 1067485312 kB
MemFree: 1057470400 kB
MemAvailable: 1057322048 kB
Buffers: 5760 kB
Would be one hell of a machine to generate endgame tables..
-
- Posts: 2662
- Joined: Wed Mar 10, 2010 10:18 pm
- Location: Hamburg, Germany
- Full name: Srdja Matovic
Re: Interesting machine
is there any performance loss compared to big endian when running code in little endian mode on these Power8 cpus?
--
Srdja
--
Srdja
-
- Posts: 20943
- Joined: Mon Feb 27, 2006 7:30 pm
- Location: Birmingham, AL
Re: Interesting machine
I don't have any endian-specific code, so not for me. I consistently number bits as LSB = 0, MSB = 63. Regardless of how they are stored in memory.smatovic wrote:is there any performance loss compared to big endian when running code in little endian mode on these Power8 cpus?
--
Srdja
I am temporarily using pthread_spin_lock() in place of my asm code, but I am probably going to rewrite the ASM code in ppc assembly language to be sure it is doing what I expect. Seems to be working well, however.
I have noticed that transparent huge pages are not working on this box (running linux kernel 3.10.0. Not yet sure why. I also noticed that large page size is 16mb rather than intel's 2mb norm. But it is running, so I am running my full 1 to 20 core parallel search test 4x per number of cores to get some data for parallel speedup.
I also noticed that the process scheduler is hopelessly confused on this box. Our 2660 box numbers cores (with hyper threading on which we usually disable) as 0-19 are on physical cores 0 - 19, and 20-39 wrap around and are also on physical cores 0-19. So 0,20 share a physical core, etc. The IBM PPC box has 8 hyper threads per CPU, with zero through 7 on physical core 0, 8 through 15 on physical core 1, etc. Don't yet know whether that is confusing the kernel's attempt at managing processor affinity or not. But I hard-code affinity which solves it completely.
I went back and re-read your post and think I mis-interpreted your question. You were asking about any speed difference if the processor itself is run in big-endian or little-endian mode? No data there, yet. I had assumed it is running in big-endian mode but will have to figure out how to check. Probably have to write some code for this.
-
- Posts: 2662
- Joined: Wed Mar 10, 2010 10:18 pm
- Location: Hamburg, Germany
- Full name: Srdja Matovic
Re: Interesting machine
Yes, this was my intended question.You were asking about any speed difference if the processor itself is run in big-endian or little-endian mode?
I have read about Power8 cpus with little endian mode to enable support for Nvidia Cuda GPUs...so i wonder if there is any performance difference between big/little endian mode on these machines.
--
Srdja
-
- Posts: 20943
- Joined: Mon Feb 27, 2006 7:30 pm
- Location: Birmingham, AL
Re: Interesting machine
The DEC alpha had the same facility and I didn't measure any difference with it. It really only affects how stuff is stored in memory which likely has zero effect in terms of processor speed.smatovic wrote:Yes, this was my intended question.You were asking about any speed difference if the processor itself is run in big-endian or little-endian mode?
I have read about Power8 cpus with little endian mode to enable support for Nvidia Cuda GPUs...so i wonder if there is any performance difference between big/little endian mode on these machines.
--
Srdja
-
- Posts: 5566
- Joined: Tue Feb 28, 2012 11:56 pm
Re: Interesting machine
Indeed...bob wrote:Would be one hell of a machine to generate endgame tables..