On Tue, Sep 18, 2012 at 06:03:59PM +0400, Glauber Costa wrote:
> From: Suleiman Souhlal <ssouhlal@xxxxxxxxxxx>
>
> mem_cgroup_do_charge() was written before kmem 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 or 3 pages (and
> both the stack 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.
>
> Fix that by passing down a minsize argument in addition to the csize.
>
> And what to do about that (csize == PAGE_SIZE && ret) retry? If it's
Wow, that patch set has been around for a while. It's been nr_pages
== 1 for a while now :-)
> needed at all (and presumably is since it's there, perhaps to handle
> races), then it should be extended to more than PAGE_SIZE, yet how far?
> And should there be a retry count limit, of what? For now retry up to
> COSTLY_ORDER (as page_alloc.c does) and make sure not to do it if
> __GFP_NORETRY.
>
> [v4: fixed nr pages calculation pointed out by Christoph Lameter ]
>
> Signed-off-by: Suleiman Souhlal <suleiman@xxxxxxxxxx>
> Signed-off-by: Glauber Costa <glommer@xxxxxxxxxxxxx>
> Reviewed-by: Kamezawa Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> Acked-by: Michal Hocko <mhocko@xxxxxxx>
> ---
> mm/memcontrol.c | 16 +++++++++-------
> 1 file changed, 9 insertions(+), 7 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 9d3bc72..b12121b 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2232,7 +2232,8 @@ enum {
> };
>
> static int mem_cgroup_do_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
> - unsigned int nr_pages, bool oom_check)
> + unsigned int nr_pages, unsigned int min_pages,
> + bool oom_check)
I'm not a big fan of the parameter names. Can we make this function
officially aware of batching and name the parameters like the
arguments that are passed in? I.e. @batch and @nr_pages?
> {
> unsigned long csize = nr_pages * PAGE_SIZE;
> struct mem_cgroup *mem_over_limit;
> @@ -2255,18 +2256,18 @@ static int mem_cgroup_do_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
> } else
> mem_over_limit = mem_cgroup_from_res_counter(fail_res, res);
> /*
> - * nr_pages can be either a huge page (HPAGE_PMD_NR), a batch
> - * of regular pages (CHARGE_BATCH), or a single regular page (1).
> - *
> * Never reclaim on behalf of optional batching, retry with a
> * single page instead.
"[...] with the amount of actually required pages instead."
> */
> - if (nr_pages == CHARGE_BATCH)
> + if (nr_pages > min_pages)
> return CHARGE_RETRY;
if (batch > nr_pages)
return CHARGE_RETRY;
But that is all just nitpicking. Functionally, it looks sane, so:
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
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