From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753213AbdCHNEA (ORCPT ); Wed, 8 Mar 2017 08:04:00 -0500 Received: from mx2.suse.de ([195.135.220.15]:52342 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753138AbdCHND5 (ORCPT ); Wed, 8 Mar 2017 08:03:57 -0500 Date: Wed, 8 Mar 2017 10:32:40 +0100 From: Michal Hocko To: Matthew Wilcox Cc: Andrew Morton , Al Viro , Vlastimil Babka , David Rientjes , Cristopher Lameter , linux-mm@kvack.org, LKML Subject: Re: [PATCH] mm, vmalloc: use __GFP_HIGHMEM implicitly Message-ID: <20170308093239.GE11028@dhcp22.suse.cz> References: <20170307141020.29107-1-mhocko@kernel.org> <20170307182841.GS16328@bombadil.infradead.org> <20170307185748.GU16328@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170307185748.GU16328@bombadil.infradead.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 07-03-17 10:57:48, Matthew Wilcox wrote: > On Tue, Mar 07, 2017 at 10:28:41AM -0800, Matthew Wilcox wrote: > > On Tue, Mar 07, 2017 at 03:10:20PM +0100, Michal Hocko wrote: > > > This patch simply uses __GFP_HIGHMEM implicitly when allocating pages to > > > be mapped to the vmalloc space. Current users which add __GFP_HIGHMEM > > > are simplified and drop the flag. > > btw, I had another idea for GFP_HIGHMEM -- remove it when CONFIG_HIGHMEM > isn't enabled. Saves 26 bytes of .text and 64 bytes of .data on my > laptop's kernel build. What do you think? I wouldn't be opposed. The downside would be a slight confusion when printing gfp flags but we already have this for ___GFP_NOLOCKDEP ;) > Also, I suspect the layout of bits is suboptimal from an assembly > language perspective. I still mostly care about x86 which doesn't > benefit, so I'm not inclined to do the work, but certainly ARM, PA-RISC, > SPARC and Itanium would all benefit from having frequently-used bits > (ie those used in GFP_KERNEL and GFP_ATOMIC) placed in the low 8 bits. be careful that there is some elaborate logic around low gfp bits to map to proper zones and ALLOC_ constants. > diff --git a/include/linux/gfp.h b/include/linux/gfp.h > index 0fe0b6295ab5..d88cb532d7c8 100644 > --- a/include/linux/gfp.h > +++ b/include/linux/gfp.h > @@ -16,7 +16,11 @@ struct vm_area_struct; > > /* Plain integer GFP bitmasks. Do not use this directly. */ > #define ___GFP_DMA 0x01u > +#ifdef CONFIG_HIGHMEM > #define ___GFP_HIGHMEM 0x02u > +#else > +#define ___GFP_HIGHMEM 0x0u > +#endif > #define ___GFP_DMA32 0x04u > #define ___GFP_MOVABLE 0x08u > #define ___GFP_RECLAIMABLE 0x10u Anyway, thanks for your review! -- Michal Hocko SUSE Labs