From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759367AbbIVTz6 (ORCPT ); Tue, 22 Sep 2015 15:55:58 -0400 Received: from smtp.transmode.se ([31.15.61.139]:56493 "EHLO smtp.transmode.se" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756639AbbIVTz5 convert rfc822-to-8bit (ORCPT ); Tue, 22 Sep 2015 15:55:57 -0400 From: Joakim Tjernlund To: "scottwood@freescale.com" CC: "christophe.leroy@c-s.fr" , "paulus@samba.org" , "mpe@ellerman.id.au" , "benh@kernel.crashing.org" , "linux-kernel@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" Subject: Re: [PATCH v2 22/25] powerpc32: move xxxxx_dcache_range() functions inline Thread-Topic: [PATCH v2 22/25] powerpc32: move xxxxx_dcache_range() functions inline Thread-Index: AQHQ9VspxrgpWLe1w0WBxWBczXIu3p5IuDyAgAANAICAAAnwgIAAAhwAgAAD2QA= Date: Tue, 22 Sep 2015 19:55:53 +0000 Message-ID: <1442951752.29498.58.camel@transmode.se> References: <1442945547.29498.50.camel@transmode.se> <1442948339.19102.270.camel@freescale.com> <1442950473.29498.54.camel@transmode.se> <1442950926.19102.280.camel@freescale.com> In-Reply-To: <1442950926.19102.280.camel@freescale.com> Accept-Language: en-US, sv-SE Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-mailer: Evolution 3.16.5 x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [192.168.200.4] Content-Type: text/plain; charset="iso-8859-15" Content-ID: Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2015-09-22 at 14:42 -0500, Scott Wood wrote: > On Tue, 2015-09-22 at 19:34 +0000, Joakim Tjernlund wrote: > > On Tue, 2015-09-22 at 13:58 -0500, Scott Wood wrote: > > > On Tue, 2015-09-22 at 18:12 +0000, Joakim Tjernlund wrote: > > > > On Tue, 2015-09-22 at 18:51 +0200, Christophe Leroy wrote: > > > > > flush/clean/invalidate _dcache_range() functions are all very > > > > > similar and are quite short. They are mainly used in __dma_sync() > > > > > perf_event locate them in the top 3 consumming functions during > > > > > heavy ethernet activity > > > > > > > > > > They are good candidate for inlining, as __dma_sync() does > > > > > almost nothing but calling them > > > > > > > > > > Signed-off-by: Christophe Leroy > > > > > --- > > > > > New in v2 > > > > > > > > > > arch/powerpc/include/asm/cacheflush.h | 55 > > > > > +++++++++++++++++++++++++++-- > > > > > arch/powerpc/kernel/misc_32.S | 65 -------------------------- > > > > > ---- > > > > > ----- > > > > > arch/powerpc/kernel/ppc_ksyms.c | 2 ++ > > > > > 3 files changed, 54 insertions(+), 68 deletions(-) > > > > > > > > > > diff --git a/arch/powerpc/include/asm/cacheflush.h > > > > > b/arch/powerpc/include/asm/cacheflush.h > > > > > index 6229e6b..6169604 100644 > > > > > --- a/arch/powerpc/include/asm/cacheflush.h > > > > > +++ b/arch/powerpc/include/asm/cacheflush.h > > > > > @@ -47,12 +47,61 @@ static inline void > > > > > __flush_dcache_icache_phys(unsigned long physaddr) > > > > > } > > > > > #endif > > > > > > > > > > -extern void flush_dcache_range(unsigned long start, unsigned long > > > > > stop); > > > > > #ifdef CONFIG_PPC32 > > > > > -extern void clean_dcache_range(unsigned long start, unsigned long > > > > > stop); > > > > > -extern void invalidate_dcache_range(unsigned long start, unsigned > > > > > long > > > > > stop); > > > > > +/* > > > > > + * Write any modified data cache blocks out to memory and invalidate > > > > > them. > > > > > + * Does not invalidate the corresponding instruction cache blocks. > > > > > + */ > > > > > +static inline void flush_dcache_range(unsigned long start, unsigned > > > > > long > > > > > stop) > > > > > +{ > > > > > + void *addr = (void *)(start & ~(L1_CACHE_BYTES - 1)); > > > > > + unsigned int size = stop - (unsigned long)addr + (L1_CACHE_BYTES - > > > > > 1); > > > > > + unsigned int i; > > > > > + > > > > > + for (i = 0; i < size >> L1_CACHE_SHIFT; i++, addr += > > > > > L1_CACHE_BYTES) > > > > > + dcbf(addr); > > > > > + if (i) > > > > > + mb(); /* sync */ > > > > > +} > > > > > > > > This feels optimized for the uncommon case when there is no > > > > invalidation. > > > > > > If you mean the "if (i)", yes, that looks odd. > > > > Yes. > > > > > > > > > I THINK it would be better to bail early > > > > > > Bail under what conditions? > > > > test for "i = 0" and return. > > Why bother? I usally find it better to dela with special cases upfront så the rest doesn't need to bother. i=0 is a NOP and it is clearer to show that upfront. > > > > > > > > > > and use do { .. } while(--i); instead. > > > > > > GCC knows how to optimize loops. Please don't make them less readable. > > > > Been a while since I checked but it used to be bad att transforming post > > inc to pre inc/dec > > I remain unconvinced until I have seen it. > > I would expect it to use bdnz for this loop, as the loop variable isn't > referenced in the loop body. > > And generally the one proposing uglification-for-optimization should provide > the evidence. :-) When it comes to gcc, past history is my evidence until proven otherwise :) Maybe I will check again ...