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Date: Thu, 13 Sep 2007 00:10:54 +0100 From: Antoine Martin <antoine@...afix.co.uk> To: Linux Kernel Development <linux-kernel@...r.kernel.org> Subject: CFS: some bad numbers with Java/database threading -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 Hi list, I was working on some unit tests and thought I'd give CFS a whirl to see if it had any impact on my workloads (to see what the fuss was about), and I came up with some pretty disturbing numbers: http://devloop.org.uk/documentation/database-performance/Linux-Kernels/Kernels-ManyThreads-CombinedTests-noload2.png As above but also showing the load average: http://devloop.org.uk/documentation/database-performance/Linux-Kernels/Kernels-ManyThreads-CombinedTests2.png Looks like a regression to me... Basically, all the previous kernels are pretty close (2.6.16 through to 2.6.20 performed almost identically to 2.6.22 and are not shown here to avoid cluttering the graphs) All the 2.6.23-rc kernels performed poorly (except -rc3!): much more erratically and with a sharp performance drop above 800 threads. The load starts to go up and the performance takes a nosedive. With fewer threads (less than 50) there is hardly any difference at all between all the kernels. Notes about the tests and setup: * environment is: Dual Opteron 252 with 3GB ram, scsi disk, etc.. Sun Java 1.6 MySQL 5.0.44 Junit + ant + my test code (devloop.org.uk) * java threads are created first and the data is prepared, then all the threads are started in a tight loop. Each thread runs multiple queries with a 10ms pause (to allow the other threads to get scheduled) * load average is divided by the number of cpus (2) * more general information (which also covers some irrelevant information about some other tests I have published) is here: http://devloop.org.uk/documentation/database-performance/Setup/ Don't shoot the messenger! I can run some more tests if needed (bearing in mind that a full test run takes a few hours) or you can run the tests yourself: instructions on running the tests are included. I am now re-testing with sched-cfs-v2.6.23-rc6-v21-combo-2.patch but feel free to send some other patches. Antoine -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.6 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFG6HH+GK2zHPGK1rsRCl3oAJ9c4crCtNQfGs9gWO7Y5CvcIno8TACbBPTw 0TEHkqLMGAfH0ILwWVKc0oo= =1iBA -----END PGP SIGNATURE----- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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