Re: mpc880 linux-2.6.32 slow running processes

Rafael Beims [off-list ref] wrote on 2011/01/10 17:35:38:

quoted

Once you have tested it and it works, please send a patch to remove the 8xx workaround.
Make sure Scott is cc:ed

I tested linux-2.6.33 on my ppc880 board today, and even without the
slowdown.patch applied, the board runs processes with good
performance.
It really seems that the problem is solved from linux-2.6.33 on.

I'm not sure what you mean by sending a patch to remove the
workaround. The only thing that I did in the 2.6.32 version was to
apply the slowdown.patch attached in the message from Michael.

Could you clarify please?

Yes, this part in arch/powerpc/mm/pgtable.c:
#ifdef CONFIG_8xx
			/* On 8xx, cache control instructions (particularly
			 * "dcbst" from flush_dcache_icache) fault as write
			 * operation if there is an unpopulated TLB entry
			 * for the address in question. To workaround that,
			 * we invalidate the TLB here, thus avoiding dcbst
			 * misbehaviour.
			 */
			/* 8xx doesn't care about PID, size or ind args */
			_tlbil_va(addr, 0, 0, 0);
#endif /* CONFIG_8xx */

Should be removed in >= 2.6.33 kernels.
My 8xx TLB work fixes this problem more efficiently.

    Jocke