On Tue, 10 Oct 2017 13:43:43 +0800 Aaron Lu <aaron.lu@xxxxxxxxx> wrote: > On Mon, Oct 09, 2017 at 10:19:52PM -0700, Dave Hansen wrote: > > On 10/09/2017 07:56 PM, Aaron Lu wrote: > > > This patch adds inline to __rmqueue() and vmlinux' size doesn't have any > > > change after this patch according to size(1). > > > > > > without this patch: > > > text data bss dec hex filename > > > 9968576 5793372 17715200 33477148 1fed21c vmlinux > > > > > > with this patch: > > > text data bss dec hex filename > > > 9968576 5793372 17715200 33477148 1fed21c vmlinux > > > > This is unexpected. Could you double-check this, please? > > mm/page_alloc.o has size changes: > > Without this patch: > $ size mm/page_alloc.o > text data bss dec hex filename > 36695 9792 8396 54883 d663 mm/page_alloc.o > > With this patch: > $ size mm/page_alloc.o > text data bss dec hex filename > 37511 9792 8396 55699 d993 mm/page_alloc.o > > But vmlinux doesn't. > > It's not clear to me what happened, do you want to me dig this out? There's weird stuff going on. With x86_64 gcc-4.8.4 Patch not applied: akpm3:/usr/local/google/home/akpm/k/25> nm mm/page_alloc.o|grep __rmqueue 0000000000002a00 t __rmqueue Patch applied: akpm3:/usr/local/google/home/akpm/k/25> nm mm/page_alloc.o|grep __rmqueue 000000000000039f t __rmqueue_fallback 0000000000001220 t __rmqueue_smallest So inlining __rmqueue has caused the compiler to decide to uninline __rmqueue_fallback and __rmqueue_smallest, which largely undoes the effect of your patch. `inline' is basically advisory (or ignored) in modern gcc's. So gcc has felt free to ignore it in __rmqueue_fallback and __rmqueue_smallest because gcc thinks it knows best. That's why we created __always_inline, to grab gcc by the scruff of its neck. So... I think this patch could do with quite a bit more care, tuning and testing with various gcc versions. -- 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>
