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On Fri, Jun 21, 2002 at 04:15:54PM +0200, Jakub Jelinek wrote: > On Fri, Jun 21, 2002 at 01:10:30PM +0200, Jeroen Dekkers wrote: > > On Fri, Jun 21, 2002 at 12:42:03PM +0200, Jakub Jelinek wrote: > > > On Fri, Jun 21, 2002 at 02:02:10PM +0400, Peter Zaitsev wrote: > > > > Also I would not agree about such architecture. Thread-per client > > > > architecture is quite convenient for many applications. Not only > > > > > > It may be convenient, but it also means you don't care > > > at all about wasting system resources (every thread currently eats some > > > unswappable kernel stack, its userland stack, etc.). Also, on IA-32 there > > > is hardware limitation that you can have only up to 8192 threads > > > in one application (though glibc limits this to 1024 threads normally). > > > > You are talking about Linux, right? But glibc also runs on other > > systems with other kernels which don't have the same limitation as > > Linux has. > > It is in fact not a Linux limitation. IA-32 LDT can have only 8192 segments, > and TLS ABI mandates %gs:0 as thread pointer. > Well, maybe you could get around this if kernel knew everything about what > is %gs used for and why, then you could only use a few GDT entries (the same > number as CPUs) and at every context switch save/restore what was pointed > by %gs:0, assuming nothing other than %gs:0 is used, but dunno how > it would go together with apps using segment registers for other things. We don't use the LDT for this, we have a constant %gs:0 pointing to a location in memory and that location has a pointer to the thread-local storage. On context switches the pointer at the address %gs:0 points to is changed. (At least if I understand Roland's changes to Mach correctly) Jeroen Dekkers -- Jabber ID: jdekkers@jabber.org IRC ID: jeroen@openprojects GNU supporter - http://www.gnu.org
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