Re: cvs commit: src/lib/libthread_xu Makefile pthread.map src/lib/libthread_xu/arch Makefile.inc src/lib/libthread_xu/arch/alpha Makefile.inc src/lib/libthread_xu/arch/alpha/alpha pthread_md.c src/lib/libthread_xu/arch/alpha/include pthread_md.h src/lib/libthread_xu/arch/amd64 ...

[Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxx>]

:We have to touch the page tables for a process switch anyway, it's not
:that expensive to have a thread-local page mapping there I think.
:On the other hand the LDT approach costs for every access.
:
:Joerg

    The rfork'd processes are sharing the same page table, and the switch
    code detects this and does not bother to reload %cr3 (which saves a lot
    of cpu cycles), so you can't create a thread-local page mapping that way.

    As far as I know the LDT is the only way to create uniqueness between
    different processes sharing the same page table.  It's expensive, but 
    probably not as expensive as reloading %cr3.

    It would be interesting to test that hypothesis... what is more expensive?
    reloading %cr3 on every switch or reloading the LDT on every switch ?

					-Matt
					Matthew Dillon 
					<dillon@xxxxxxxxxxxxx>