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[209.85.220.65]) by mx.google.com with SMTPS id t3sor6780130ybp.193.2019.02.26.08.31.55 for (Google Transport Security); Tue, 26 Feb 2019 08:31:55 -0800 (PST) Received-SPF: pass (google.com: domain of dennisszhou@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; spf=pass (google.com: domain of dennisszhou@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=dennisszhou@gmail.com; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org X-Google-Smtp-Source: AHgI3IaDYm6I0be+SHNf29F3AQM1X/gSL2A4NS43BZxsGCnY1RuKykUsFHiaOxgDbTdpbCjn9pPc2g== X-Received: by 2002:a25:8882:: with SMTP id d2mr19048907ybl.381.1551198715061; Tue, 26 Feb 2019 08:31:55 -0800 (PST) Received: from dennisz-mbp.dhcp.thefacebook.com ([2620:10d:c091:200::2:7f17]) by smtp.gmail.com with ESMTPSA id f188sm4204686ywb.64.2019.02.26.08.31.53 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 26 Feb 2019 08:31:53 -0800 (PST) Date: Tue, 26 Feb 2019 11:31:51 -0500 From: Dennis Zhou To: Christopher Lameter Cc: "dennis@kernel.org" , Peng Fan , "tj@kernel.org" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "van.freenix@gmail.com" Subject: Re: [PATCH 2/2] percpu: km: no need to consider pcpu_group_offsets[0] Message-ID: <20190226163151.GA47262@dennisz-mbp.dhcp.thefacebook.com> References: <20190224132518.20586-1-peng.fan@nxp.com> <20190224132518.20586-2-peng.fan@nxp.com> <20190225151616.GB49611@dennisz-mbp.dhcp.thefacebook.com> <010001692a605709-407cf476-e7b6-43be-8551-66c54059e92f-000000@email.amazonses.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <010001692a605709-407cf476-e7b6-43be-8551-66c54059e92f-000000@email.amazonses.com> User-Agent: Mutt/1.10.1 (2018-07-13) 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 Tue, Feb 26, 2019 at 03:15:50PM +0000, Christopher Lameter wrote: > On Mon, 25 Feb 2019, dennis@kernel.org wrote: > > > > @@ -67,7 +67,7 @@ static struct pcpu_chunk *pcpu_create_chunk(gfp_t gfp) > > > pcpu_set_page_chunk(nth_page(pages, i), chunk); > > > > > > chunk->data = pages; > > > - chunk->base_addr = page_address(pages) - pcpu_group_offsets[0]; > > > + chunk->base_addr = page_address(pages); > > > > > > spin_lock_irqsave(&pcpu_lock, flags); > > > pcpu_chunk_populated(chunk, 0, nr_pages, false); > > > -- > > > 2.16.4 > > > > > > > While I do think you're right, creating a chunk is not a part of the > > critical path and subtracting 0 is incredibly minor overhead. So I'd > > rather keep the code as is to maintain consistency between percpu-vm.c > > and percpu-km.c. > > Well it is confusing if there the expression is there but never used. It > is clearer with the patch. > Okay. I'll apply it with your ack if that's fine. Thanks, Dennis