Re: [PATCH] per-page SLAB freeing (only dcache for now)

[Andrew Morton <akpm@osdl.org>]

Marcelo Tosatti <marcelo.tosatti@cyclades.com> wrote:
>
> ...
> +unsigned long long slab_free_status(kmem_cache_t *cachep, struct slab *slabp)
> +{
> +	unsigned long long bitmap = 0;
> +	int i;
> +
> +	if (cachep->num > sizeof(unsigned long long)*8)
> +		BUG();
> +
> +	spin_lock_irq(&cachep->spinlock);
> +	for(i=0; i < cachep->num ; i++) {
> +		if (slab_bufctl(slabp)[i] == BUFCTL_INUSE)
> +			set_bit(i, (unsigned long *)&bitmap);
> +	}
> +	spin_unlock_irq(&cachep->spinlock);
> +
> +	return bitmap;
> +}

What if there are more than 64 objects per page?

> +        if (!ops)
> +                BUG();
> +	if (!PageSlab(page))
> +		BUG();
> +	if (slabp->s_mem != (page_address(page) + slabp->colouroff))
> +		BUG();
> +
> +        if (PageLocked(page))
> +                return 0;

There's quite a lot of whitespace breakage btw.


It all seems rather complex.

What about simply compacting the cache by copying freeable dentries? 
Something like, in prune_one_dentry():

	if (dcache occupancy < 90%) {
		new_dentry = alloc_dentry()
		*new_dentry = *dentry;
		<fix stuff up>
		free(dentry);
	} else {
		free(dentry)
	}

?

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