On Thu, 16 Jul 2015 09:19:49 +0200 Michal Hocko <mhocko@xxxxxxxxxx> wrote: > On Wed 15-07-15 13:57:11, Andrew Morton wrote: > > On Wed, 15 Jul 2015 13:14:41 +0200 Michal Hocko <mhocko@xxxxxxxxxx> wrote: > > > > > mem_cgroup structure is defined in mm/memcontrol.c currently which > > > means that the code outside of this file has to use external API even > > > for trivial access stuff. > > > > > > This patch exports mm_struct with its dependencies and makes some of the > > > exported functions inlines. This even helps to reduce the code size a bit > > > (make defconfig + CONFIG_MEMCG=y) > > > > > > text data bss dec hex filename > > > 12355346 1823792 1089536 15268674 e8fb42 vmlinux.before > > > 12354970 1823792 1089536 15268298 e8f9ca vmlinux.after > > > > > > This is not much (370B) but better than nothing. We also save a function > > > call in some hot paths like callers of mem_cgroup_count_vm_event which is > > > used for accounting. > > > > > > The patch doesn't introduce any functional changes. > > > > > > ... > > > > > > include/linux/memcontrol.h | 369 +++++++++++++++++++++++++++++++++++++++++---- > > > > Boy, that's a ton of new stuff into the header file. Do we actually > > *need* to expose all this? > > I am exporting struct mem_cgroup with its dependencies + some small > functions which allow to inline some really trivial code and helps to > generate a better code. > > > Is some other patch dependent on it? > > Without mem_cgroup visible outside of memcontrol.c we couldn't inline > and now we can also use some fields from mem_cgroup directly and get rid > of some really trivial access functions. > > > If > > not then perhaps we shouldn't do this - if the code was already this > > way, I'd be attracted to a patch which was the reverse of this one! > > I agree with Johannes who originally suggested to expose mem_cgroup that > it will allow for a better code later. Sure, but how *much* better? Are there a significant number of fastpath functions involved? >From a maintainability/readability point of view, this is quite a bad patch. It exposes a *lot* of stuff to the whole world. We need to get a pretty good runtime benefit from doing this to ourselves. I don't think that saving 376 bytes on a fatconfig build is sufficient justification? -- 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>