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[209.132.183.28]) by mx.google.com with ESMTPS id v20si1483942vsq.14.2019.07.11.04.38.00 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 11 Jul 2019 04:38:00 -0700 (PDT) Received-SPF: pass (google.com: domain of nitesh@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of nitesh@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=nitesh@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 93CBB3082135; Thu, 11 Jul 2019 11:37:59 +0000 (UTC) Received: from [10.18.17.163] (dhcp-17-163.bos.redhat.com [10.18.17.163]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 8C59C194B3; Thu, 11 Jul 2019 11:37:50 +0000 (UTC) Subject: Re: [RFC][PATCH v11 0/2] mm: Support for page hinting To: Dave Hansen , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, pbonzini@redhat.com, lcapitulino@redhat.com, pagupta@redhat.com, wei.w.wang@intel.com, yang.zhang.wz@gmail.com, riel@surriel.com, david@redhat.com, mst@redhat.com, dodgen@google.com, konrad.wilk@oracle.com, dhildenb@redhat.com, aarcange@redhat.com, alexander.duyck@gmail.com, john.starks@microsoft.com, mhocko@suse.com References: <20190710195158.19640-1-nitesh@redhat.com> From: Nitesh Narayan Lal Openpgp: preference=signencrypt Autocrypt: addr=nitesh@redhat.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.42]); Thu, 11 Jul 2019 11:37:59 +0000 (UTC) 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 7/10/19 4:19 PM, Dave Hansen wrote: > On 7/10/19 12:51 PM, Nitesh Narayan Lal wrote: >> This patch series proposes an efficient mechanism for reporting free m= emory >> from a guest to its hypervisor. It especially enables guests with no p= age cache >> (e.g., nvdimm, virtio-pmem) or with small page caches (e.g., ram > dis= k) to >> rapidly hand back free memory to the hypervisor. >> This approach has a minimal impact on the existing core-mm infrastruct= ure. >> >> Measurement results (measurement details appended to this email): >> *Number of 5GB guests (each touching 4GB memory) that can be launched >> without swap usage on a system with 15GB: > This sounds like a reasonable measurement, but I think you're missing a= > sentence or two explaining why this test was used. I will re-work the cover email to better communicate the numbers. > >> unmodified kernel - 2, 3rd with 2.5GB =20 > What does "3rd with 2.5GB" mean? The third gets 2.5GB before failing a= n > allocation and crashing? It doesn't crash or fail. To complete the execution of the test application which allocates 4GB memory in the 3rd guest 2.5GB swap has been accessed. > >> v11 page hinting - 6, 7th with 26MB =20 >> v1 bubble hinting[1] - 6, 7th with 1.8GB (bubble hinting is another se= ries >> proposed to solve the same problems) > Could you please make an effort to format things so that reviewers can > easily read them? Aligning columns and using common units would be ver= y > helpful, for instance: > > unmodified kernel - 2, 3rd with 2.50 GB > v11 page hinting - 6, 7th with 0.03 GB > v1 bubble hinting[1] - 6, 7th with 1.80 GB > > See how you can scan that easily and compare between the rows? > > I think you did some analysis below. But, that seems misplaced. It's > better to include the conclusion here and the details to back it up > later. As it stands, the cover letter just throws some data at a > reviewer and hopes they can make sense of it. I will improve this. Thanks. > >> *Memhog execution time (For 3 guests each of 6GB on a system with 15GB= ): >> unmodified kernel - Guest1:21s, Guest2:27s, Guest3:2m37s swap used =3D= 3.7GB =20 >> v11 page hinting - Guest1:23s, Guest2:26s, Guest3:21s swap used =3D 0 = =20 >> v1 bubble hinting - Guest1:23, Guest2:11s, Guest3:26s swap used =3D 0 = =20 > Again, I'm finding myself having to reformat your data just so I can > make sense of it. You also forgot the unit for Guest 1 in row 3. > > unmodified - Guest1:21s, Guest2:27s, Guest3:2m37s swap used =3D 3.7G= B > > v11 hinting - Guest1:23s, Guest2:26s, Guest3:21s swap used =3D 0 > v1 bubble - Guest1:23s, Guest2:11s, Guest3:26s swap used =3D 0 > > So, what is this supposed to show? What does it mean? Why do the > numbers vary *so* much? Basically, the idea was to communicate that with hinting swap was not accessed and hence the time of execution is lower. But as you already mentioned next time around I will format this and add the conclusion along with these numbers. I agree with Alexander's comment that there is no point of having the same thing at two place. --=20 Thanks Nitesh