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Tue, 17 Dec 2019 17:24:51 +0000 (UTC) Received: from [10.36.116.87] (ovpn-116-87.ams2.redhat.com [10.36.116.87]) by smtp.corp.redhat.com (Postfix) with ESMTP id 299191000322; Tue, 17 Dec 2019 17:24:39 +0000 (UTC) Subject: Re: [PATCH v15 3/7] mm: Add function __putback_isolated_page To: Alexander Duyck , Alexander Duyck , kvm@vger.kernel.org, mst@redhat.com, linux-kernel@vger.kernel.org, willy@infradead.org, mhocko@kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, mgorman@techsingularity.net, vbabka@suse.cz Cc: yang.zhang.wz@gmail.com, nitesh@redhat.com, konrad.wilk@oracle.com, pagupta@redhat.com, riel@surriel.com, lcapitulino@redhat.com, dave.hansen@intel.com, wei.w.wang@intel.com, aarcange@redhat.com, pbonzini@redhat.com, dan.j.williams@intel.com, osalvador@suse.de References: <20191205161928.19548.41654.stgit@localhost.localdomain> <20191205162230.19548.70198.stgit@localhost.localdomain> <9eb9173278370dd604c4cefd30ed10be36600854.camel@linux.intel.com> <8a4b0337-0bad-2978-32e8-6f90c7365f00@redhat.com> <753e2991e3e632b9c179c45197bfb05669625e9a.camel@linux.intel.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: <753e2991e3e632b9c179c45197bfb05669625e9a.camel@linux.intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>> Also there are some scenarios where __page_to_pfn is not that simple= a >>> call with us having to get the node ID so we can find the pgdat struc= ture >>> to perform the calculation. I'm not sure the compiler would be ble to >>> figure out that the result is the same for both calls, so it is bette= r to >>> make it explicit. >> >> Only in case of CONFIG_SPARSEMEM we have to go via the section - but I >> doubt this is really worth optimizing here. >> >> But yeah, I'm fine with this change, only "IMHO >> get_pageblock_migratetype() would be nicer" :) >=20 > Aren't most distros running with CONFIG_SPARSEMEM enabled? If that is t= he > case why not optimize for it? Because I tend to dislike micro-optimizations without performance numbers for code that is not on a hot path. But I mean in this case, as you said, you need the pfn either way, so it's completely fine with. I do wonder, however, if you should just pass in the migratetype from the caller. That would be even faster ;) --=20 Thanks, David / dhildenb