[Devel] Re: [PATCH v3 05/28] memcg: Reclaim when more than one page needed.

[Christoph Lameter]

On Fri, 25 May 2012, Glauber Costa wrote:

> From: Suleiman Souhlal <ssouhlal at FreeBSD.org>
>
> mem_cgroup_do_charge() was written before slab accounting, and expects
> three cases: being called for 1 page, being called for a stock of 32 pages,
> or being called for a hugepage.  If we call for 2 pages (and several slabs
> used in process creation are such, at least with the debug options I had),
> it assumed it's being called for stock and just retried without reclaiming.

Slab pages are allocated up to order 3 (PAGE_ALLOC_COSTLY_ORDER). That is
8 pages.

>  	 * unlikely to succeed so close to the limit, and we fall back
>  	 * to regular pages anyway in case of failure.
>  	 */
> -	if (nr_pages == 1 && ret)
> +	if (nr_pages <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER) && ret) {
> +		cond_resched();
>  		return CHARGE_RETRY;
> +	}
>
>  	/*
>  	 * At task move, charge accounts can be doubly counted. So, it's

Ok. That looks correct.