Messages in this thread | | | Date | Mon, 30 Mar 2009 13:12:55 -0700 (PDT) | From | David Rientjes <> | Subject | Re: [patch 1/3] slub: add per-cache slab thrash ratio |
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On Mon, 30 Mar 2009, Christoph Lameter wrote:
> > @@ -2291,10 +2292,13 @@ static int calculate_sizes(struct kmem_cache *s, int forced_order) > > /* > > * Determine the number of objects per slab > > */ > > + if (oo_objects(s->oo)) > > + thrash_ratio = s->min_free_watermark * 100 / oo_objects(s->oo); > > s->oo = oo_make(order, size); > > s->oo is set *after* you check it. Check oo_objects after the value has > been set please. >
It's actually right the way I implemented it, oo_objects(s->oo) will be 0 when this is called for kmem_cache_open() meaning there is no preexisting slab_thrash_ratio. But this check is required when calculate_sizes() is called from order_store() to adjust the slab_thrash_ratio for the new objects per slab. The above check is saving the old thrash ratio so the new s->min_free_watermark value can be set following the oo_make(). This was mentioned in the changelog for this patch:
The value is stored in terms of the number of objects that the ratio represents, not the ratio itself. This avoids costly arithmetic in the slowpath for a calculation that could otherwise be done only when `slab_thrash_ratio' or `order' is changed.
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