From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f200.google.com (mail-qk0-f200.google.com [209.85.220.200]) by kanga.kvack.org (Postfix) with ESMTP id EE64A6B0653 for ; Thu, 10 May 2018 23:24:48 -0400 (EDT) Received: by mail-qk0-f200.google.com with SMTP id h15-v6so3388262qkh.3 for ; Thu, 10 May 2018 20:24:48 -0700 (PDT) Received: from mail1.bemta8.messagelabs.com (mail1.bemta8.messagelabs.com. [216.82.243.202]) by mx.google.com with ESMTPS id l63-v6si2167531qkd.341.2018.05.10.20.24.47 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 10 May 2018 20:24:47 -0700 (PDT) From: Huaisheng HS1 Ye Subject: RE: [External] Re: [PATCH v1] include/linux/gfp.h: getting rid of GFP_ZONE_TABLE/BAD Date: Fri, 11 May 2018 03:24:34 +0000 Message-ID: References: <1525968625-40825-1-git-send-email-yehs1@lenovo.com> <20180510163023.GB30442@bombadil.infradead.org> In-Reply-To: <20180510163023.GB30442@bombadil.infradead.org> Content-Language: zh-CN Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Matthew Wilcox Cc: "akpm@linux-foundation.org" , "linux-mm@kvack.org" , "mhocko@suse.com" , "vbabka@suse.cz" , "mgorman@techsingularity.net" , "alexander.levin@verizon.com" , "colyli@suse.de" , NingTing Cheng , "linux-kernel@vger.kernel.org" > From: owner-linux-mm@kvack.org [mailto:owner-linux-mm@kvack.org] On Behal= f Of Matthew > Wilcox > On Fri, May 11, 2018 at 12:10:25AM +0800, Huaisheng Ye wrote: > > -#define __GFP_DMA ((__force gfp_t)___GFP_DMA) > > -#define __GFP_HIGHMEM ((__force gfp_t)___GFP_HIGHMEM) > > -#define __GFP_DMA32 ((__force gfp_t)___GFP_DMA32) > > +#define __GFP_DMA ((__force gfp_t)OPT_ZONE_DMA ^ ZONE_NORMAL) > > +#define __GFP_HIGHMEM ((__force gfp_t)ZONE_MOVABLE ^ ZONE_NORMAL) > > +#define __GFP_DMA32 ((__force gfp_t)OPT_ZONE_DMA32 ^ ZONE_NORMAL) >=20 > No, you've made gfp_zone even more complex than it already is. > If you can't use OPT_ZONE_HIGHMEM here, then this is a waste of time. >=20 Dear Matthew, The reason why I don't use OPT_ZONE_HIGHMEM for __GFP_HIGHMEM directly is = that, for x86_64 platform there is no CONFIG_HIGHMEM, so OPT_ZONE_HIGHMEM s= hall always be equal to ZONE_NORMAL. For gfp_zone it is impossible to distinguish the meaning of lowest 3 bits i= n flags. How can gfp_zone to understand it comes from OPT_ZONE_HIGHMEM or Z= ONE_NORMAL? And the most pained thing is that, if __GFP_HIGHMEM with movable flag enabl= ed, it means that ZONE_MOVABLE shall be returned. That is different from ZONE_DMA, ZONE_DMA32 and ZONE_NORMAL. I was thinking... Whether it is possible to use other judgement condition to decide OPT_ZONE_= HIGHMEM or ZONE_MOVABLE shall be returned from gfp_zone. Sincerely, Huaisheng Ye > > static inline enum zone_type gfp_zone(gfp_t flags) > > { > > enum zone_type z; > > - int bit =3D (__force int) (flags & GFP_ZONEMASK); > > + z =3D ((__force unsigned int)flags & ___GFP_ZONE_MASK) ^ ZONE_NORMAL; > > + > > + if (z > OPT_ZONE_HIGHMEM) > > + z =3D OPT_ZONE_HIGHMEM + > > + !!((__force unsigned int)flags & ___GFP_MOVABLE); > > > > - z =3D (GFP_ZONE_TABLE >> (bit * GFP_ZONES_SHIFT)) & > > - ((1 << GFP_ZONES_SHIFT) - 1); > > - VM_BUG_ON((GFP_ZONE_BAD >> bit) & 1); > > + VM_BUG_ON(z > ZONE_MOVABLE); > > return z; > > }