Re: 2.6.22 -mm merge plans: slub

On Tue, 1 May 2007, Christoph Lameter wrote:

On Tue, 1 May 2007, Hugh Dickins wrote:

quoted

Yes, to me it does.  If it could be defaulted to on throughout the
-rcs, on every architecture, then I'd say that's "finishing work";
and we'd be safe knowing we could go back to slab in a hurry if
needed.  But it hasn't reached that stage yet, I think.

Why would we need to go back to SLAB if we have not switched to SLUB? SLUB 
is marked experimental and not the default.

I said above that I thought SLUB ought to be defaulted to on throughout
the -rcs: if we don't do that, we're not going to learn much from having
it in Linus' tree.

And perhaps that line which appends "PREEMPT " to an oops report ought
to append "SLUB " too, for so long as there's a choice.

The only problems that I am aware of is(or was) the issue with arches 
modifying page struct fields of slab pages that SLUB needs for its own 
operations. And I thought it was all fixed since the powerpc guys were 
quiet and the patch was in for i386.

You're forgetting your unions in struct page: in the SPLIT_PTLOCK
case (NR_CPUS >= 4) the pagetable code is using spinlock_t ptl,
which overlays SLUB's first_page and slab pointers.

I just tried rebuilding powerpc with the SPLIT_PTLOCK cutover
edited to 8 cpus instead, and then no crash.

I presume the answer is just to extend your quicklist work to
powerpc's lowest level of pagetables.  The only other architecture
which is using kmem_cache for them is arm26, which has
"#error SMP is not supported", so won't be giving this problem.

Hugh

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>