Date: Fri, 08 Mar 2013 09:58:17 -0800 From: Xin Li <delphij@delphij.net> To: FreeBSD Current <freebsd-current@freebsd.org>, Andriy Gapon <avg@freebsd.org> Subject: FULL_PREEMPTION Message-ID: <513A26B9.7060305@delphij.net>
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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 Hi, I have seen a few posts from Andriy as as well as the PC-BSD default that for desktop systems, kern.sched.preempt_thresh=224 would improve responsiveness. Looking at the code, it seems that this is equivalent to compiling the kernel with FULL_PREEMPTION. The sys/conf/NOTES says, however: # FULL_PREEMPTION instructs the kernel to preempt non-realtime kernel # threads. Its sole use is to expose race conditions and other # bugs during development. Enabling this option will reduce # performance and increase the frequency of kernel panics by # design. If you aren't sure that you need it then you don't. # Relies on the PREEMPTION option. DON'T TURN THIS ON. Despite the possibility of exposing race conditions as well as potentially hurting throughput because of (possibly more) context switching, is it considered as a goal that we should support it? If so, should we enable it on -CURRENT? Cheers, - -- Xin LI <delphij@delphij.net> https://www.delphij.net/ FreeBSD - The Power to Serve! Live free or die -----BEGIN PGP SIGNATURE----- iQEcBAEBCgAGBQJROia5AAoJEG80Jeu8UPuzv7MIAKoBNZyR28E5Wdnj2+IkHXvi Vg9TipTxAWSyCBcuywJEoZUCXZs1f/WbGOrbPQv0iS9AWFt9GZJ+arVsk23hwVdw kRredDAoF4kMR85wo0h8Zl04comNN+pdPNlftCGc4B6J63ysg1m7KlhUAHyXWLW9 lS7wleILiF1HRhggq7qBj4OChgbWUUgUBqf9ZMraLQMyFvfdnktE3OkDBOE1J0zu QgEdAtQ2RL5JkocsqGziq4zWKGjqM60WLQAR/5i8sCP+oQ5qRbIebUpc/GKWY7r8 mAQDwrvKU26pbHSWOkT0Qi9cXw+GGG2vTU6fLh1e0p2QBgzpyXO2TfpkL6kioQA= =xenl -----END PGP SIGNATURE-----
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