Messages in this thread | | | Date | Fri, 24 Feb 2006 15:06:50 -0500 | From | Gautam H Thaker <> | Subject | Re: ~5x greater CPU load for a networked application when using 2.6.15-rt15-smp vs. 2.6.12-1.1390_FC4 |
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Andrew Morton wrote: > Ingo Molnar <mingo@elte.hu> wrote: > >>To figure out the true overhead of both kernels, could you try the >> attached loop_print_thread.c code
> http://www.zip.com.au/~akpm/linux/#zc <- better ;)
Andrew,
I read the README for the "zc" tests. I wish Ingo can opine on which may be a better test. Also, i assume that I can run "zcs" and "zcc" on the same machine. I would do the tests with "send" instead of "sendfile".
I also have some other test data. The graphical summary result can be viewed at this link:
http://www.atl.external.lmco.com/projects/QoS/LM_ATL_MW_Comparator_7920.png
In these tests I used a single Intel Xeon 3GH dual processor machine with 4 different kernels, all based on 2.6.14
2.6.14 Uniprocessor kernel 2.6.14-rt22 Uniprocessor kernel w/ RT patches 2.6.14-smp SMP kernel 2.6.14-rt22-smp SMP kernel w/ RT patches.
The test is similar to "zcs", "zcc" tests. In my tests a client process opens a TCP connection to the server process (all on same machine) and sends to it 10,000,000 messages of sizes 4 bytes, 8 bytes, 16 bytes, .... , 32Kbytes, 64Kbytes. The server sends back a 1 byte reply. The client measures roundtrip latencies. The graphic shows mean roundtrip latencies. Since measuremnts are taken over so many samples I believe that the large differences in mean latencies capture the relative CPU consumption of various kernel. (This being loopback there are no NIC card issues or otherwise.) One notices a 3:1 ration here from uniprocessor, non-RT kernel to SMP-RT kernel. The RT kernel has nice real-time properties, and there is a lot of pressure in our systems to use the SMP hardware of the multicore machines, and in some cases we can even with with a 3x slowdown (since real applications do more than just I/O), but when I started to note 5x (or more) in my newer tests I thought I would at least post something.
I suspect that "zcs"/"zcc" tests would pretty much show the same conclusions as this graphic.
Gautam H. Thaker Distributed Processing Lab; Lockheed Martin Adv. Tech. Labs 3 Executive Campus; Cherry Hill, NJ 08002 856-792-9754, fax 856-792-9925 email: gthaker@atl.lmco.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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