![]() | |||||||||||||
Messages in this thread |
Con Kolivas <kernel@kolivas.org> wrote: > > > Zwane M suggested using tbench as a load to test one of his recent patches and > gave me the idea to try using tbench_load in contest. Here are the first set > of results I got while running tbench 4 continuously (uniprocessor machine): > > tbench_load: > Kernel [runs] Time CPU% > test2420 1 180 38.9 > test2561 1 970 7.7 > > This is a massive difference. Sure tbench was giving better numbers on 2.5.61 > but it caused a massive slowdown. I wondered whether this translates into > being more susceptible to ping floods or DDOS attacks? You should have seen > tbench 16 - 3546 seconds! > Yes, something is wrong with the CPU scheduler. Simple test case: ./tbench_srv & while true do ./tbench 4 done & cd /usr/src/util-linux time make -j4 The tbench activity takes the time to compile util-linux from 13 second to 133 seconds. But that is not the whole story. The compilation appeared to make no progress at all while tbench was running - it was only in the gaps between ending one tbench run and starting another that the compilation did anything. When I changed the load to one instance of while true do ./tbench 2 done and one instance of while true do ./tbench 3 done the compilation made no progress except for those rare instances when the two shell scripts were restarting the tbench run at the same time. After a while the scripts fell itno synchronism, and the compilation took 260 seconds. Conclusion: tbench completely starves the `make'. It mainly seems to affect uniprocessor builds. SMP was much better behaved. Adding the sched-f3 patch basicaly fixed it all up. The 133 second build came down to 55 seconds, and the compilation was visibly making progress during the tbench runs. - 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/ | ||||||||||||
| Last update: 2005-03-22 12:33 [from the cache] ©2003-2008 | |||||||||||||