Re: [rfc][patch] SLQB slab allocator

MinChan Kim
2008-12-15T23:40:45Z

Hi, Nick.
I am interested in SLQB.
So I tested slqb, slub, slab by kernel compile time.

make all -j 8

slqb and slub not DEBUG.
my test environment is as follows.

cpu family : 6
model : 15
model name : Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz
stepping : 11
cpu MHz : 1600.000
cache size : 4096 KB

Below is average for ten time test.

slab :
user : 2376.484, system : 192.616 elapsed : 12:22.0
slub :
user : 2378.439, system : 194.989 elapsed : 12:22.4
slqb :
user : 2380.556, system : 194.801 elapsed : 12:23.0

so, slqb is rather slow although it is a big difference.
Interestingly, slqb consumes less time than slub in system.

And I found some trivial bug. :)

<snip>

> +static struct slqb_page *new_slab_page(struct kmem_cache *s, gfp_t flags, int node)
> +{
> + struct slqb_page *page;
> + void *start;
> + void *last;
> + void *p;
> +
> + BUG_ON(flags & GFP_SLAB_BUG_MASK);
> +
> + page = allocate_slab(s,
> + flags & (GFP_RECLAIM_MASK | GFP_CONSTRAINT_MASK), node);
> + if (!page)
> + goto out;
> +
> + page->flags |= 1 << PG_slab;

PG_slab set is redundant.
It's already set in alloc_slqb_pags_node.

> + start = page_address(&page->page);
> +
> + if (unlikely(slab_poison(s)))
> + memset(start, POISON_INUSE, PAGE_SIZE << s->order);

<snip>

> +void kfree(const void *object)
> +{
> + struct kmem_cache *s;
> + struct page *p;
> + struct slqb_page *page;
> + unsigned long flags;
> +
> + if (unlikely(ZERO_OR_NULL_PTR(object)))
> + return;
> +
> + p = virt_to_page(object);
> + prefetch(p);
> + prefetchw(object);
> +
> +#ifdef CONFIG_SLQB_DEBUG
> + page = (struct slqb_page *)compound_head(p);
> + s = page->list->cache;
> + debug_check_no_locks_freed(object, s->objsize);
> + if (likely(object) && unlikely(slab_debug(s))) {
> + if (unlikely(!free_debug_processing(s, object, __builtin_return_address(0))))
> + return;
> + }
> +#endif
> +
> + local_irq_save(flags);
> +#ifndef CONFIG_SLQB_DEBUG
> + page = (struct slqb_page *)compound_head(p);
> + s = page->list->cache;
> +#endif

If it is not defined CONFIG_SLQB_DEBUG, page is garbage.

> + __slab_free(s, page, object);
> + local_irq_restore(flags);
> +}
> +EXPORT_SYMBOL(kfree);
> +

--
Kinds regards,
MinChan Kim
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