On Thu, 2015-07-16 at 11:17 -0700, David Miller wrote: > From: Tom Herbert <t...@herbertland.com> > Date: Thu, 16 Jul 2015 08:43:25 -0700 > > > On Thu, Jul 16, 2015 at 5:40 AM, Denys Vlasenko <dvlas...@redhat.com> wrote: > >> This patch deinlines jhash, jhash2 and __jhash_nwords. > >> > >> It also removes rhashtable_jhash2(key, length, seed) > >> because it was merely calling jhash2(key, length, seed). > >> > >> With this .config: http://busybox.net/~vda/kernel_config, > >> after deinlining these functions have sizes and callsite counts > >> as follows: > >> > >> __jhash_nwords: 72 bytes, 75 calls > >> jhash: 297 bytes, 111 calls > >> jhash2: 205 bytes, 136 calls > >> > > jhash is used in several places in the critical data path. Does the > > decrease in text size justify performance impact of not inlining it? > > Tom took the words right out of my mouth. > > Denys, you keep making deinlining changes like this all the time, like > a robot. But I never see you make any effort to look into the performance > nor code generation ramifications of your changes. > > And frankly that makes your patches quite tiring to deal with. > > Your changes potentially have large performance implications, yet you > don't put any effort into considering that aspect at all.
It might be useful to have these performance impacting changes guarded by something like CONFIG_CC_OPTIMIZE_FOR_SIZE with another static __always_inline __<func> and a function & EXPORT_SYMBOL or just a static inline so that where code size is critical it's uninlined. Though even for tiny embedded uses, the additional code complexity might not be worth it. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
