Re: Inefficient TLB flushing

[Andrew Morton <akpm@osdl.org>]

Jack Steiner <steiner@sgi.com> wrote:
>
> > Either that, or add a new interface function
>  > 
>  > 	int mmu_gather_is_full_mm(mmu_gather *tlb);
>  > 
>  > and use it...
>  > 
> 
>  How implementation independent should it be? Currently, there is only one
>  field in the mmu_gather structure that must be preserved. However, if we
>  want to make the interface truly implementation independent, it seems
>  like we should define something like:
> 
>  	if (need_resched()) {
>  		struct mmu_gather_state state;
>  		tlb_mmu_gather_save_state(*tlbp, &state);
>  		tlb_finish_mmu(*tlbp, tlb_start, start);
>  		...
>  		*tlbp = tlb_mmu_gather_restore_state(&state);
>  	}
> 
>  Is this overkill?

Think so ;) The `full_mm_flush' boolean is the only state thing we can pass
into tlb_gather_mmu anyway.

> 
>  Should we use the patch given above for 2.6.0 & replace it with an implementation 
>  independent interface for 2.6.1?

Just the little wrapper which doesn't assume the presence of
mmu_gather.full_mm should suffice.