On Mon, Nov 03, 2014 at 11:06:07PM +0200, Kirill A. Shutemov wrote: > On Sat, Nov 01, 2014 at 11:15:54PM -0400, Johannes Weiner wrote: > > Memory cgroups used to have 5 per-page pointers. To allow users to > > disable that amount of overhead during runtime, those pointers were > > allocated in a separate array, with a translation layer between them > > and struct page. > > > > There is now only one page pointer remaining: the memcg pointer, that > > indicates which cgroup the page is associated with when charged. The > > complexity of runtime allocation and the runtime translation overhead > > is no longer justified to save that *potential* 0.19% of memory. > > How much do you win by the change? Heh, that would have followed right after where you cut the quote: with CONFIG_SLUB, that pointer actually sits in already existing struct page padding, which means that I'm saving one pointer per page (8 bytes per 4096 byte page, 0.19% of memory), plus the pointer and padding in each memory section. I also save the (minor) translation overhead going from page to page_cgroup and the maintenance burden that stems from having these auxiliary arrays (see deleted code). -- 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>