On Sat, Nov 07, 2015 at 05:53:38PM +0100, Jesper Dangaard Brouer wrote: > On Thu, 5 Nov 2015 19:25:14 +0300 > Vladimir Davydov <vdavydov@xxxxxxxxxxxxx> wrote: > > > On Thu, Nov 05, 2015 at 04:38:06PM +0100, Jesper Dangaard Brouer wrote: > > > Initial implementation missed support for kmem cgroup support > > > in kmem_cache_free_bulk() call, add this. > > > > > > If CONFIG_MEMCG_KMEM is not enabled, the compiler should > > > be smart enough to not add any asm code. > > > > > > Signed-off-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx> > > > > > > --- > > > V2: Fixes according to input from: > > > Vladimir Davydov <vdavydov@xxxxxxxxxxxxx> > > > and Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> > > > > > > mm/slub.c | 3 +++ > > > 1 file changed, 3 insertions(+) > > > > > > diff --git a/mm/slub.c b/mm/slub.c > > > index 8e9e9b2ee6f3..bc64514ad1bb 100644 > > > --- a/mm/slub.c > > > +++ b/mm/slub.c > > > @@ -2890,6 +2890,9 @@ void kmem_cache_free_bulk(struct kmem_cache *s, size_t size, void **p) > > > do { > > > struct detached_freelist df; > > > > > > + /* Support for memcg */ > > > + s = cache_from_obj(s, p[size - 1]); > > > + > > > > AFAIU all objects in the array should come from the same cache (should > > they?), so it should be enough to call this only once: > > Can we be sure all objects in the array come from same cache? > > Imagine my use case: > 1. application send packet alloc a SKB (from a slab) > 2. packet TX to NIC via DMA > 3. TX DMA completion cleans up 256 packets and kmem free SKBs > > I don't know enough about mem cgroups... but I can imagine two > applications belonging to different mem-cgroups sending packet out same > NIC and later getting their SKB (pkt-metadata struct) free'ed during > the same TX completion (TX softirq) cycle, as a bulk free. Hmm, I thought that a bunch of objects allocated using kmem_cache_alloc_bulk must be freed using kmem_cache_free_bulk. If it does not hold, i.e. if one can allocate an array of objects one by one using kmem_cache_alloc and then batch-free them using kmem_cache_free_bulk, then my proposal is irrelevant. > > With my limited mem cgroups, it looks like memcg works on the slab-page > level? Yes, a memcg has its private copy of each global kmem cache it attempted to use, which implies that all objects on the same slab-page must belong to the same memcg. > And what I'm doing in this code is to group object together > belonging to the same slab-page. Yeah, after inspecting build_detached_freelist more closely, I see your patch is correct. Feel free to add Reviewed-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx> Thanks, Vladimir -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>