On Wed, Sep 18, 2013 at 12:38:23PM +0200, Knut Petersen wrote:
On 18.09.2013 11:10, Daniel Vetter wrote:
Just now I prepared a patch changing the same function in vmscan.c
Also, this needs to be rebased to the new shrinker api in 3.12, I simply haven't rolled my trees forward yet.
Well, you should. Since commit 81e49f shrinker->count_objects might be set to SHRINK_STOP, causing shrink_slab_node() to complain loud and often:
[ 1908.234595] shrink_slab: i915_gem_inactive_scan+0x0/0x9c negative objects to delete nr=-xxxxxxxxx
The kernel emitted a few thousand log lines like the one quoted above during the last few days on my system.
diff --git a/mm/vmscan.c b/mm/vmscan.c index 2cff0d4..d81f6e0 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -254,6 +254,10 @@ unsigned long shrink_slab(struct shrink_control *shrink, total_scan = max_pass; }
/* Always try to shrink a bit to make forward progress. */if (shrinker->evicts_to_page_lru)total_scan = max_t(long, total_scan, batch_size);At that place the error message is already emitted.
/* * We need to avoid excessive windup on filesystem shrinkers * due to large numbers of GFP_NOFS allocations causing theHave a look at the attached patch. It fixes my problem with the erroneous/misleading error messages, and I think it´s right to just bail out early if SHRINK_STOP is found.
Do you agree ?
No, that's wrong. ->count_objects should never ass SHRINK_STOP. Indeed, it should always return a count of objects in the cache, regardless of the context.
SHRINK_STOP is for ->scan_objects to tell the shrinker it can make any progress due to the context it is called in. This allows the shirnker to defer the work to another call in a different context. However, if ->count-objects doesn't return a count, the work that was supposed to be done cannot be deferred, and that is what ->count_objects should always return the number of objects in the cache.
Cheers,
Dave.