On 03/26/2013 12:43 PM, Michal Hocko wrote: > On Tue 26-03-13 12:35:58, Glauber Costa wrote: >>>> >>>> I doubt it's a win to add 4K to kernel text size instead of adding >>>> a few extra lines of code... but it's up to you. >>> >>> I will leave the decision to Glauber. The updated version which uses >>> kmalloc for the static buffer is bellow. >>> >> I prefer to allocate dynamically here. But although I understand why we >> need to call cgroup_name, I don't understand what is wrong with >> kasprintf if we're going to allocate anyway. It will allocate a string >> just big enough. A PAGE_SIZE'd allocation is a lot more likely to fail. >> >> Now, if we really want to be smart here, we can do something like what >> I've done for the slub attribute buffers, that can actually have very >> long values. >> >> allocate a small buffer that will hold 80 % > of the allocations (256 >> bytes should be enough for most cache names), and if the string is >> bigger than this, we allocate. Once we allocate, we save it in a static >> pointer and leave it there. The hope here is that we may be able to >> live without ever allocating in many systems. >> >>> + >>> + /* >>> + * kmem_cache_create_memcg duplicates the given name and >>> + * cgroup_name for this name requires RCU context. >>> + * This static temporary buffer is used to prevent from >>> + * pointless shortliving allocation. >>> + */ >> The comment is also no longer true if you don't resort to a static buffer. > > The buffer _is_ static (read global variable hidden with the function > scope). > Although correct, it is a bit misleading. It is static in the sense it is held by a static variable. But it is acquired by kmalloc... In any way, this is a tiny detail. FWIW, I am fine with the patch you provided: Acked-by: Glauber Costa <glommer@xxxxxxxxxxxxx> We could go seeing how big those allocations are in practice, but I doubt it is worth the trouble. -- 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>