From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f176.google.com (mail-pd0-f176.google.com [209.85.192.176]) by kanga.kvack.org (Postfix) with ESMTP id EB8DD6B0035 for ; Tue, 22 Apr 2014 03:39:14 -0400 (EDT) Received: by mail-pd0-f176.google.com with SMTP id r10so4574382pdi.35 for ; Tue, 22 Apr 2014 00:39:14 -0700 (PDT) Received: from ozlabs.org (ozlabs.org. [103.22.144.67]) by mx.google.com with ESMTPS id w4si22222701paa.485.2014.04.22.00.39.13 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 22 Apr 2014 00:39:13 -0700 (PDT) From: Rusty Russell Subject: Re: [PATCH V2 1/2] mm: move FAULT_AROUND_ORDER to arch/ In-Reply-To: <53456B61.1040901@intel.com> References: <1396592835-24767-1-git-send-email-maddy@linux.vnet.ibm.com> <1396592835-24767-2-git-send-email-maddy@linux.vnet.ibm.com> <533EDB63.8090909@intel.com> <5344A312.80802@linux.vnet.ibm.com> <53456B61.1040901@intel.com> Date: Tue, 22 Apr 2014 16:52:17 +0930 Message-ID: <87vbu1hlqu.fsf@rustcorp.com.au> MIME-Version: 1.0 Content-Type: text/plain Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen , Madhavan Srinivasan , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, x86@kernel.org Cc: benh@kernel.crashing.org, paulus@samba.org, kirill.shutemov@linux.intel.com, akpm@linux-foundation.org, riel@redhat.com, mgorman@suse.de, ak@linux.intel.com, peterz@infradead.org, mingo@kernel.org Dave Hansen writes: > On 04/08/2014 06:32 PM, Madhavan Srinivasan wrote: >>> > In mm/Kconfig, put >>> > >>> > config FAULT_AROUND_ORDER >>> > int >>> > default 1234 if POWERPC >>> > default 4 >>> > >>> > The way you have it now, every single architecture that needs to enable >>> > this has to go put that in their Kconfig. That's madness. This way, >> I though about it and decided not to do this way because, in future, >> sub platforms of the architecture may decide to change the values. Also, >> adding an if line for each architecture with different sub platforms >> oring to it will look messy. > > I'm not sure why I'm trying here any more. You do seem quite content to > add as much cruft to ppc and every other architecture as possible. If > your theoretical scenario pops up, you simply do this in ppc: > > config ARCH_FAULT_AROUND_ORDER > int > default 999 > default 888 if OTHER_SILLY_POWERPC_SUBARCH > > But *ONLY* in the architectures that care about doing that stuff. You > leave every other architecture on the planet alone. Then, in mm/Kconfig: > > config FAULT_AROUND_ORDER > int > default ARCH_FAULT_AROUND_ORDER if ARCH_FAULT_AROUND_ORDER > default 4 > > Your way still requires going and individually touching every single > architecture's Kconfig that wants to enable fault around. That's not an > acceptable solution. Why bother with Kconfig at all? It seems like a weird indirection. And talking about future tuning seems like a separate issue, if and when someone does the work. For the moment, let's keep it simple (as below). If you really want Kconfig, then just go straight from ARCH_FAULT_AROUND_ORDER, ie: #ifdef CONFIG_ARCH_FAULT_AROUND_ORDER #define FAULT_AROUND_ORDER CONFIG_ARCH_FAULT_AROUND_ORDER #else #define FAULT_AROUND_ORDER 4 #endif Then powerpc's Kconfig defines CONFIG_ARCH_FAULT_AROUND_ORDER, and we're done. Cheers, Rusty. diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h index 32e4e212b9c1..b519c5c53cfc 100644 --- a/arch/powerpc/include/asm/page.h +++ b/arch/powerpc/include/asm/page.h @@ -412,4 +412,7 @@ typedef struct page *pgtable_t; #include #endif /* __ASSEMBLY__ */ +/* Measured on a 4 socket Power7 system (128 Threads and 128GB memory) */ +#define FAULT_AROUND_ORDER 3 + #endif /* _ASM_POWERPC_PAGE_H */ diff --git a/mm/memory.c b/mm/memory.c index d0f0bef3be48..9aa47e9ec7ba 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3382,7 +3382,10 @@ void do_set_pte(struct vm_area_struct *vma, unsigned long address, update_mmu_cache(vma, address, pte); } +/* Archs can override, but this seems to work for x86. */ +#ifndef FAULT_AROUND_ORDER #define FAULT_AROUND_ORDER 4 +#endif #ifdef CONFIG_DEBUG_FS static unsigned int fault_around_order = FAULT_AROUND_ORDER; -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org