Re: cvs commit: src/lib/libthread_xu Makefile pthread.map src/li
Joerg Sonnenberger wrote:
> On Tue, Feb 01, 2005 at 03:14:47PM -0800, Matthew Dillon wrote:
>
>>: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.
>
>
> But you can still share most parts of the page table, if you exploit
> the two level approach.
>
Yes, you can rewrite a pte, but an invlpg intruction is very expensive!
remember you have to operate TLB, which should be avoided in most time.
> Joerg
>
>
>> -Matt
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