From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f46.google.com (mail-pa0-f46.google.com [209.85.220.46]) by kanga.kvack.org (Postfix) with ESMTP id 981876B0039 for ; Wed, 27 Aug 2014 19:18:57 -0400 (EDT) Received: by mail-pa0-f46.google.com with SMTP id eu11so141397pac.5 for ; Wed, 27 Aug 2014 16:18:57 -0700 (PDT) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id ss8si3439805pab.0.2014.08.27.16.18.56 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 27 Aug 2014 16:18:56 -0700 (PDT) Date: Wed, 27 Aug 2014 16:18:54 -0700 From: Andrew Morton Subject: Re: [PATCH 1/2] x86: Optimize resource lookups for ioremap Message-Id: <20140827161854.0619a04653b336d3adc755f3@linux-foundation.org> In-Reply-To: <53FE6515.6050102@sgi.com> References: <20140827225927.364537333@asylum.americas.sgi.com> <20140827225927.602319674@asylum.americas.sgi.com> <20140827160515.c59f1c191fde5f788a7c42f6@linux-foundation.org> <53FE6515.6050102@sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Mike Travis Cc: mingo@redhat.com, tglx@linutronix.de, hpa@zytor.com, msalter@redhat.com, dyoung@redhat.com, riel@redhat.com, peterz@infradead.org, mgorman@suse.de, linux-kernel@vger.kernel.org, x86@kernel.org, linux-mm@kvack.org, Alex Thorlton On Wed, 27 Aug 2014 16:09:09 -0700 Mike Travis wrote: > > >> > >> ... > >> > >> --- linux.orig/kernel/resource.c > >> +++ linux/kernel/resource.c > >> @@ -494,6 +494,43 @@ int __weak page_is_ram(unsigned long pfn > >> } > >> EXPORT_SYMBOL_GPL(page_is_ram); > >> > >> +/* > >> + * Search for a resouce entry that fully contains the specified region. > >> + * If found, return 1 if it is RAM, 0 if not. > >> + * If not found, or region is not fully contained, return -1 > >> + * > >> + * Used by the ioremap functions to insure user not remapping RAM and is as > >> + * vast speed up over walking through the resource table page by page. > >> + */ > >> +int __weak region_is_ram(resource_size_t start, unsigned long size) > >> +{ > >> + struct resource *p; > >> + resource_size_t end = start + size - 1; > >> + int flags = IORESOURCE_MEM | IORESOURCE_BUSY; > >> + const char *name = "System RAM"; > >> + int ret = -1; > >> + > >> + read_lock(&resource_lock); > >> + for (p = iomem_resource.child; p ; p = p->sibling) { > >> + if (end < p->start) > >> + continue; > >> + > >> + if (p->start <= start && end <= p->end) { > >> + /* resource fully contains region */ > >> + if ((p->flags != flags) || strcmp(p->name, name)) > >> + ret = 0; > >> + else > >> + ret = 1; > >> + break; > >> + } > >> + if (p->end < start) > >> + break; /* not found */ > >> + } > >> + read_unlock(&resource_lock); > >> + return ret; > >> +} > >> +EXPORT_SYMBOL_GPL(region_is_ram); > > > > Exporting a __weak symbol is strange. I guess it works, but neither > > the __weak nor the export are actually needed? > > > > I mainly used 'weak' and export because that was what the page_is_ram > function was using. Most likely this won't be used anywhere else but > I wasn't sure. I can certainly remove the weak and export, at least > until it's actually needed? Several architectures implement custom page_is_ram(), so they need the __weak. region_is_ram() needs neither so yes, they should be removed. Doing strcmp("System RAM") is rather a hack. Is there nothing in resource.flags which can be used? Or added otherwise? -- 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