Messages in this thread |  | | Date | Mon, 30 Oct 2000 09:26:59 +0100 (CET) | From | Ingo Molnar <> | Subject | Re: 2.2.18Pre Lan Performance Rocks! |
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On Mon, 30 Oct 2000, Andi Kleen wrote:
> One problem in Linux 2.2 is that kernel threads reload their VM on > context switch (that would include the nfsd thread), this should be > fixed in 2.4 with lazy mm. Hmm actually it should be only fixed for > true kernel threads that have been started with kernel_thread(), the > "pseudo kernel threads" like nfsd uses probably do not get that > optimization because they don't set their MM to init_mm.
yes, but for this there is an explicit mechanizm to lazy-MM during lengthy system calls, an example is in buffer.c:
user_mm = start_lazy_tlb(); error = sync_old_buffers(); end_lazy_tlb(user_mm);
> > to get disproportiantely higher in Linux than NetWare 5.x and when it hits > > 60% of total clock cycles, Linux starts dropping off. NetWare 5.x is 1/8 > > I think that can be explained by the copying.
yes. Constant copying contaminates the L1/L2 caches and creates dirty cachelines all around the place. Fixed in 2.4 + TUX ;-)
Ingo
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