(2013/03/29 18:13), Glauber Costa wrote:
> In very low free kernel memory situations, it may be the case that we
> have less objects to free than our initial batch size. If this is the
> case, it is better to shrink those, and open space for the new workload
> then to keep them and fail the new allocations.
>
> More specifically, this happens because we encode this in a loop with
> the condition: "while (total_scan >= batch_size)". So if we are in such
> a case, we'll not even enter the loop.
>
> This patch modifies turns it into a do () while {} loop, that will
> guarantee that we scan it at least once, while keeping the behaviour
> exactly the same for the cases in which total_scan > batch_size.
>
> Signed-off-by: Glauber Costa <glommer@xxxxxxxxxxxxx>
> Reviewed-by: Dave Chinner <david@xxxxxxxxxxxxx>
> Reviewed-by: Carlos Maiolino <cmaiolino@xxxxxxxxxx>
> CC: "Theodore Ts'o" <tytso@xxxxxxx>
> CC: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> ---
> mm/vmscan.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
Doesn't this break
==
/*
* copy the current shrinker scan count into a local variable
* and zero it so that other concurrent shrinker invocations
* don't also do this scanning work.
*/
nr = atomic_long_xchg(&shrinker->nr_in_batch, 0);
==
This xchg magic ?
Thnks,
-Kame
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 88c5fed..fc6d45a 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -280,7 +280,7 @@ unsigned long shrink_slab(struct shrink_control *shrink,
> nr_pages_scanned, lru_pages,
> max_pass, delta, total_scan);
>
> - while (total_scan >= batch_size) {
> + do {
> int nr_before;
>
> nr_before = do_shrinker_shrink(shrinker, shrink, 0);
> @@ -294,7 +294,7 @@ unsigned long shrink_slab(struct shrink_control *shrink,
> total_scan -= batch_size;
>
> cond_resched();
> - }
> + } while (total_scan >= batch_size);
>
> /*
> * move the unused scan count back into the shrinker in a
>
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