On Thu, Sep 27, 2012 at 07:33:00AM -0700, Tejun Heo wrote: > Hello, Michal. > > On Thu, Sep 27, 2012 at 02:08:06PM +0200, Michal Hocko wrote: > > Yes, because we have many users (basically almost all) who care only > > about the user memory because that's what occupies the vast majority of > > the memory. They usually want to isolate workload which would disrupt > > the global memory otherwise (e.g. backup process vs. database). You > > really do not want to pay an additional overhead for kmem accounting > > here. > > I'm not too convinced. First of all, the overhead added by kmemcg > isn't big. Really? If kmemcg was globally accounted then every __GFP_KMEMCG allocation in the page allocator potentially ends up down in __memcg_kmem_newpage_charge which 1. takes RCU read lock 2. looks up cgroup from task 3. takes a reference count 4. memcg_charge_kmem -> __mem_cgroup_try_charge 5. release reference count That's a *LOT* of work to incur for cgroups that do not care about kernel accounting. This is why I thought it was reasonable that the kmem accounting not be global. -- Mel Gorman SUSE Labs -- 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>