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DragonFly commits List (threaded) for 2005-02
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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 ...

From: Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxx>
Date: Tue, 1 Feb 2005 15:14:47 -0800 (PST)

:This is an optimisation for the intra-program switch if you want to call it so.
:I would argue that the normal switch case is either user -> kernel or to
:a different kernel thread.

    You pretty much always want to have just a single page table with a
    threaded program.  The %cr3 optimization is a nice plus, but it isn't
    why the page table is being shared.  The page table is being shared
    because trying to build a threaded program WITHOUT sharing the page
    table is extremely expensive.  Every time you'd allocate memory or map
    something it would have to be replicated across N page tables.  
    Performance would be destroyed.


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