Hello, Jan. On Tue, Jun 30, 2015 at 04:31:00PM +0200, Jan Kara wrote: ... > > + if (inode_cgwb_enabled(inode)) > > + wb = wb_get_create_current(bdi, GFP_KERNEL); > > + if (!wb) > > + wb = &bdi->wb; > > + > > So this effectively adds a radix tree lookup (of wb belonging to memcg) for > every set_page_dirty() call. That seems relatively costly to me. And all Hmmm... idk, radix tree lookups should be cheap especially when shallow and set_page_dirty(). It's a glorified array indexing. If not, we should really be improving radix tree implementation. That said, > that just to check wb->dirty_exceeded. Cannot we just use inode_to_wb() > instead? I understand results may be different if multiple memcgs share an > inode and that's the reason why you use wb_get_create_current(), right? > But for dirty_exceeded check it may be good enough? Yeah, that probably should work. I'll think more about it. Thanks. -- tejun -- 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>