Re: Any reason for passing "tlb" to "free_pgtables()" by address?

Hugh Dickins
2006-05-09T11:23:07Z

On Mon, 8 May 2006, Zoltan Menyhart wrote:
>
> Could you please explain what your plans are?

Nick already answered, and I agree with his answer;
but I get the feeling you'd like to hear it from me too.

My plan (as his) is to rework the mmu_gather TLB flush batching
so that it can be done without disabling preemption, so that it
does not add to latency.

Nick uses the pagetables themselves as buffering, I allocate a
temporary buffer: in each case we abandon the per-cpu arrays which
need preemption disabled. But neither patch is good enough yet.

> How much do you think it is worth to optimize "free_pgtables()",
> knowing that:
> - PTE, PMD and PUD pages are freed seldom (wrt. the leaf pages)
> - The number of these pages is much more less than
> that of the leaf pages.

Not worth much at all in comparison: it just falls automatically
out of the mmu_gathering rework which covers the leaf pages too.

But free_pgtables is where I got caught out inadvertently adding
latency in 2.6.15, so I've a responsibility to correct that case.

Hugh