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[209.85.220.65]) by mx.google.com with SMTPS id b15sor4046997pfb.23.2019.03.20.19.17.34 for (Google Transport Security); Wed, 20 Mar 2019 19:17:34 -0700 (PDT) Received-SPF: pass (google.com: domain of zbestahu@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=LI6Pwpnp; spf=pass (google.com: domain of zbestahu@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=zbestahu@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=thSPW+DbNyo/B6n0hblHK9PLdW84i8rPMI1jjSEdyzE=; b=LI6PwpnpQ92HB00y16XO2SI6qWg9n7wSZ4F/O+61BlrKyDJ7HGGwMnqxdAcH0Fis5t JYMNy9JEnSoodmBmoaI5tq4M4toMcYvVpNnr37g1+zs9/zNVd6Ln+ns3RhoEOqXPs+sd fJEIXiNfbRPJFxxPR8Z1AEJSy/6B6Nb92X4WHwzvL1XfJ7NXQs305EEgbeyk4goQHVv6 4AFDYd6bDAiQZ3qwlkub3je2sgnh+Zphq8zsWYuDLMfP5CpHCBsDVJvb//TjyHjM6px3 rZffcEqZiuonAV/itsYMU5DkWXX5YnlG/uZlFGuBiPzASdb2k1CdUHDtkoh/KGNb+FES bniA== X-Google-Smtp-Source: APXvYqwoJhIIGpas5lhZvTnUrMsQiQfmzyToN39SYYfDiPH8wan45oLPsQ6IPZM2Kz6fnO2XW+c8lA== X-Received: by 2002:a62:55c7:: with SMTP id j190mr983047pfb.226.1553134653801; Wed, 20 Mar 2019 19:17:33 -0700 (PDT) Received: from localhost ([218.189.10.173]) by smtp.gmail.com with ESMTPSA id j71sm7326588pfc.6.2019.03.20.19.17.31 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 20 Mar 2019 19:17:33 -0700 (PDT) Date: Thu, 21 Mar 2019 10:17:21 +0800 From: Yue Hu To: Andrew Morton Cc: iamjoonsoo.kim@lge.com, mingo@kernel.org, vbabka@suse.cz, rppt@linux.vnet.ibm.com, rdunlap@infradead.org, linux-mm@kvack.org, huyue2@yulong.com Subject: Re: [PATCH] mm/cma: fix the bitmap status to show failed allocation reason Message-ID: <20190321101721.00006f19.zbestahu@gmail.com> In-Reply-To: <20190320151245.ff79af49fe364ac01d4edb14@linux-foundation.org> References: <20190320060829.9144-1-zbestahu@gmail.com> <20190320151245.ff79af49fe364ac01d4edb14@linux-foundation.org> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; i686-w64-mingw32) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, 20 Mar 2019 15:12:45 -0700 Andrew Morton wrote: > On Wed, 20 Mar 2019 14:08:29 +0800 Yue Hu wrote: >=20 > > Currently one bit in cma bitmap represents number of pages rather than > > one page, cma->count means cma size in pages. So to find available pages > > via find_next_zero_bit()/find_next_bit() we should use cma size not in > > pages but in bits although current free pages number is correct due to > > zero value of order_per_bit. Once order_per_bit is changed the bitmap > > status will be incorrect. =20 >=20 > When fixing a bug, please always describe the end-user visible runtime > effects of that bug? >=20 Hi Andrew, =46rom perspective of bitmap function, the size input is not correct. It will affect the available pages at some position to debug the failure issue. This is an example with order_per_bit =3D 1 Before this change: [ 4.120060] cma: number of available pages: 1@93+4@108+7@121+7@137+7@153= +7@169+7@185+7@201+3@213+3@221+3@229+3@237+3@245+3@253+3@261+3@269+3@277+3@= 285+3@293+3@301+3@309+3@317+3@325+19@333+15@369+512@512=3D> 638 free of 102= 4 total pages After this change: [ 4.143234] cma: number of available pages: 2@93+8@108+14@121+14@137+14@= 153+14@169+14@185+14@201+6@213+6@221+6@229+6@237+6@245+6@253+6@261+6@269+6@= 277+6@285+6@293+6@301+6@309+6@317+6@325+38@333+30@369=3D> 252 free of 1024 = total pages Obviously the bitmap status before is incorrect, i can add this effect desc= ribtion in v2, but seems the patch has been merged? Thx.