Messages in this thread | | | Date | Sat, 3 Nov 2007 20:03:19 +0000 (GMT) | From | Hugh Dickins <> | Subject | Re: [PATCH 2/2] slub: fix Objects count |
| |
On Sat, 3 Nov 2007, Christoph Lameter wrote: > On Sat, 3 Nov 2007, Hugh Dickins wrote: > > > I was afraid you might say something like that. > > Perhaps it'll be a patch I need to use in my own builds. > > Though I'd have thought others would want that accuracy too. > > Didn't SLAB give it? (The "r*gr*ss**n" word!) > > Slab also only counts objects that are not in the queues. See free_block() > f.e.
I'll take your word for it, and apologize for my slur on slub! (Slub has a great deal to admire in it, I should say.)
> > We could improve the situation by flushing all cpu slabs before counts are > determined. > > Which can be done manually. Run > > slabinfo -s > > and then look at the numbers.
Mmm, I'd been doing slabinfo -v sometimes. These are fine in some situations, but it's always better when the observer can avoid interfering with the observed. Impossible, we know, but...
Also, many caches too quickly re-equip themselves with cpu slabs which again obscure the numbers.
> > > Adds to much overhead to the fast paths > > > > You've come to that conclusion very quickly! > > I have just spend a few weeks optimizing the fast and slow paths and there > is some additional overhead that I am still trying to eliminate. > > > Any numbers to back it up? > > The performance in the fast paths depends on updating only a single word > for an allocation. Adding another counter makes that impossible.
Gosh, that's a tighter corner than any I've been in.
> > See the recent post on SLUB regression on SMP.
I'll have to read up on that, thanks for the pointer.
Hugh - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |