Date: Fri, 18 Jan 2013 20:16:49 -0700 From: Julian Elischer <julian@freebsd.org> To: Trent Nelson <trent@snakebite.org> Cc: Konstantin Belousov <kostikbel@gmail.com>, Ian Lepore <freebsd@damnhippie.dyndns.org>, Alfred Perlstein <bright@mu.org>, "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org> Subject: Re: Getting the current thread ID without a syscall? Message-ID: <50FA1021.6000303@freebsd.org> In-Reply-To: <20130115230330.GA53211@snakebite.org> References: <20130115205403.GA52904@snakebite.org> <20130115211641.GC2522@kib.kiev.ua> <20130115213513.GA53047@snakebite.org> <20130115214332.GE2522@kib.kiev.ua> <50F5D82C.7070400@mu.org> <1358289221.32417.129.camel@revolution.hippie.lan> <20130115230330.GA53211@snakebite.org>
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On 1/15/13 4:03 PM, Trent Nelson wrote: > On Tue, Jan 15, 2013 at 02:33:41PM -0800, Ian Lepore wrote: >> On Tue, 2013-01-15 at 14:29 -0800, Alfred Perlstein wrote: >>> On 1/15/13 1:43 PM, Konstantin Belousov wrote: >>>> On Tue, Jan 15, 2013 at 04:35:14PM -0500, Trent Nelson wrote: >>>>> Luckily it's for an open source project (Python), so recompilation >>>>> isn't a big deal. (I also check the intrinsic result versus the >>>>> syscall result during startup to verify the same ID is returned, >>>>> falling back to the syscall by default.) >>>> For you, may be. For your users, it definitely will be a problem. >>>> And worse, the problem will be blamed on the operating system and not >>>> to the broken application. >>>> >>> Anything we can do to avoid this would be best. >>> >>> The reason is that we are still dealing with an "optimization" that perl >>> did, it reached inside of the opaque struct FILE to "do nasty things". >>> Now it is very difficult for us to fix "struct FILE". >>> >>> We are still paying for this years later. >>> >>> Any way we can make this a supported interface? >>> >>> -Alfred >> Re-reading the original question, I've got to ask why pthread_self() >> isn't the right answer? The requirement wasn't "I need to know what the >> OS calls me" it was "I need a unique ID per thread within a process." > The identity check is performed hundreds of times per second. The > overhead of (Py_MainThreadId == __readgsdword(0x48) ? A() : B()) is > negligible -- I can't say the same for a system/function call. > > (I'm experimenting with an idea I had to parallelize Python such > that it can exploit all cores without impeding the performance > of normal single-threaded execution (like previous-GIL-removal > attempts and STM). It's very promising so far -- presuming we > can get the current thread ID in a couple of instructions. If > not, single-threaded performance suffers too much.) TLS? > > Trent. > _______________________________________________ > freebsd-hackers@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-hackers > To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org" >
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