[26-devel] v2.6 performance slowdown on MPC8xx: Measuring TLB cache misses

Joakim Tjernlund Joakim.Tjernlund at lumentis.se
Sun Apr 24 07:51:25 EST 2005

> On Apr 23, 2005, at 1:35 PM, Joakim Tjernlund wrote:
> > Is it possible to handle the _PAGE_ACCESSED handling at pte creation 
> > in fault.c instead
> > of doing it for every TLB miss? That should make the TLB Miss handler 
> > faster.
> No.  As part of VM management to determine working sets, it's possible 
> to have
> this flag change state but the page to remain valid.

OK, strange though. I would have expected this flag to stay untouched until the
pte is invalidated.

> The cost of 
> setting this properly
> in the miss handler is minimal compared to the other stuff that we 
> should try
> and streamline.

Well, every instruction counts. I this case we would have saved
2 in ITLB Miss, 3 in DTLB Miss and a cache line write in both.

Would be nice to do away with the kernel space test, but thats a lot harder.

> Thanks.
> 	-- Dan

More information about the Linuxppc-embedded mailing list