Messages in this thread | | | Date | Mon, 27 Dec 2004 15:55:53 -0500 | From | Brian Gerst <> | Subject | Re: 2.4, 2.6, i686/athlon and LDT's |
| |
Arjan van de Ven wrote: > On Mon, 2004-12-27 at 11:46 -0800, Tymm Twillman wrote: > >>Hi all, > > >>It appears that use of the LDT is to speed up context switching between >>threads, although I haven't even found especially good references WRT >>that. I have looked through the info in the IA Developers publications >>and have whacked my head against Google quite a bit. However, every bit >>of clarity I've found there has been offset by new confuzled bits. > > > LDT's are *slow*. That's why glibc will try to avoid using them > nowadays, and with 2.6 it won't; as for 2.4.. it depends if you use a > vendor 2.4 it might be able to avoid using LDT's as well.
Using the LDT isn't inherently slower, since the cpu caches the segment descriptor regardless of if it came from the GDT or LDT. Using an LDT however consumes kernel memory, which can slow down the system from memory pressure if you have many processes/threads using them.
-- Brian Gerst - 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/
| |