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[209.85.220.65]) by mx.google.com with SMTPS id r3sor13390421jai.10.2019.07.11.08.09.10 for (Google Transport Security); Thu, 11 Jul 2019 08:09:10 -0700 (PDT) Received-SPF: pass (google.com: domain of alexander.duyck@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=CCgbZrJc; spf=pass (google.com: domain of alexander.duyck@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=alexander.duyck@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=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=YItf/moxjUgo7takqDZFQEc1UXgT30LlS+BEwqLzypw=; b=CCgbZrJcbWzmaMpDdrUVBUdTnnC+C8Y4vkIvctOzh6QPtLu6TdwzLd/XF2HdeFLMg+ Z8H/0GK0PTciZzuykVN+q1zt7ANp+GEpd0rLXzeJ/Ure3Yyqb0kwdZvofqMxns6ch6Mx YO44ymMb/iODSwl8vhTJnJUoetpIliPECiX+jA7tD8yAUcO9rEZndw6Ch9Rsv/DUmlo2 ho/f6wnHv4Yw4/m120myNLOw2AuY/XbNS+n29ZzaCGH2kXwWYldaIdh7sUzW8r2+kKdv VoQIFuPOzCV7X8AgeOmCybtjVjzqKv5+KFM+zSTMkdewB8HK1ZXIjSe6beUzNsii7VNs 7YkQ== X-Google-Smtp-Source: APXvYqz4B2avZS+TS0M6KCibhKSyfJ1EEW1jCWEcUpjsBihdusPoizZoHVid1GFAzjKDzb4Ord/yrQ6v/K7bbprG2fg= X-Received: by 2002:a02:cd82:: with SMTP id l2mr5105904jap.96.1562857750171; Thu, 11 Jul 2019 08:09:10 -0700 (PDT) MIME-Version: 1.0 References: <20190710195158.19640-1-nitesh@redhat.com> <901cb83e-fb6a-a7fc-a60e-e35b0c89139d@redhat.com> In-Reply-To: From: Alexander Duyck Date: Thu, 11 Jul 2019 08:08:59 -0700 Message-ID: Subject: Re: [RFC][PATCH v11 0/2] mm: Support for page hinting To: Nitesh Narayan Lal Cc: kvm list , LKML , linux-mm , Paolo Bonzini , lcapitulino@redhat.com, pagupta@redhat.com, wei.w.wang@intel.com, Yang Zhang , Rik van Riel , David Hildenbrand , "Michael S. Tsirkin" , dodgen@google.com, Konrad Rzeszutek Wilk , dhildenb@redhat.com, Andrea Arcangeli , john.starks@microsoft.com, Dave Hansen , Michal Hocko Content-Type: text/plain; charset="UTF-8" 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 Thu, Jul 11, 2019 at 8:04 AM Nitesh Narayan Lal wrot= e: > > > On 7/11/19 10:58 AM, Alexander Duyck wrote: > > On Thu, Jul 11, 2019 at 4:31 AM Nitesh Narayan Lal = wrote: > >> > >> On 7/10/19 7:40 PM, Alexander Duyck wrote: > >>> On Wed, Jul 10, 2019 at 12:52 PM Nitesh Narayan Lal wrote: > >>> > >>> The results up here were redundant with what is below so I am just > >>> dropping them. I would suggest only including one set of results in > >>> any future cover page as it is confusing to duplicate it like that. > >>> > >>>> This approach tracks all freed pages of the order MAX_ORDER - 2 in b= itmaps. > >>>> A new hook after buddy merging is used to set the bits in the bitmap= . > >>>> Currently, the bits are only cleared when pages are hinted, not when= pages are > >>>> re-allocated. > >>>> > >>>> Bitmaps are stored on a per-zone basis and are protected by the zone= lock. A > >>>> workqueue asynchronously processes the bitmaps as soon as a pre-defi= ned memory > >>>> threshold is met, trying to isolate and report pages that are still = free. > >>>> > >>>> The isolated pages are reported via virtio-balloon, which is respons= ible for > >>>> sending batched pages to the host synchronously. Once the hypervisor= processed > >>>> the hinting request, the isolated pages are returned back to the bud= dy. > >>>> > >>>> Changelog in v11: > >>>> * Added logic to take care of multiple NUMA nodes scenarios. > >>>> * Simplified the logic for reporting isolated pages to the host. (Eg= . replaced > >>>> dynamically allocated arrays with static ones, introduced wait event= instead of > >>>> the loop in order to wait for a response from the host) > >>>> * Added a mutex to prevent race condition when page hinting is enabl= ed by > >>>> multiple drivers. > >>>> * Simplified the logic responsible for decrementing free page counte= r for each > >>>> zone. > >>>> * Simplified code structuring/naming. > >>>> > >>>> Known work items for the future: > >>>> * Test device assigned guests to ensure that hinting doesn't break i= t. > >>>> * Follow up on VIRTIO_BALLOON_F_PAGE_POISON's device-side support. > >>>> * Decide between MADV_DONTNEED and MADV_FREE. > >>>> * Look into memory hotplug, more efficient locking, better naming co= nventions to > >>>> avoid confusion with VIRTIO_BALLOON_F_FREE_PAGE_HINT support. > >>>> * Come up with proper/traceable error-message/logs and look into oth= er code > >>>> simplifications. (If necessary). > >>>> > >>>> Benefit analysis: > >>>> 1. Number of 5GB guests (each touching 4GB memory) that can be launc= hed without > >>>> swap usage on a system with 15GB: > >>>> unmodified kernel - 2, 3rd with 2.5GB > >>>> v11 page hinting - 6, 7th with 26MB > >>>> v1 bubble hinting - 6, 7th with 1.8GB > >>>> > >>>> Conclusion - In this particular testcase on using v11 page hinting a= nd > >>>> v1 bubble-hinting 4 more guests could be launched without swapping c= ompared > >>>> to an unmodified kernel. > >>>> For the 7th guest launch, v11 page hinting is slightly better than v= 1 Bubble > >>>> hinting as it touches lesser swap space. > >>> I'm confused by the comment. From what I can tell bubble hinting came > >>> up with 1.8GB of memory while page hinting only managed to achieve > >>> .026GB (Using the same units makes it easier to visualize the > >>> difference). Also your test says "can be launched without swap usage"= , > >>> yet you say the bubble hinting is touching swap which makes not sense > >>> to me. > >> I will work on the cover to improve this part. > >> Basically, In each case, the first number indicates the number of the > >> guest which are launched without touching the swap space. For instance > >> with bubble hinting, I was able to launch 6 guests without any swap > >> usage. On launching the 7th guests initially there was no swap usage, > >> however, as the test app starts allocating 4GB memory the swap came in= to > >> the picture. 1.8 GB is the swap usage after the completion of the test > >> application. > >>>> Setup & procedure - > >>>> Total NUMA Node Memory ~ 15 GB (All guests are run on a single NUMA = node) > >>>> Guest Memory =3D 5GB > >>>> Number of CPUs in the guest =3D 1 > >>>> Host swap =3D 4GB > >>>> Workload =3D test allocation program that allocates 4GB memory, touc= hes it via > >>>> memset and exits. > >>>> The first guest is launched and once its console is up, the test all= ocation > >>>> program is executed with 4 GB memory request (Due to this the guest = occupies > >>>> almost 4-5 GB of memory in the host in a system without page hinting= ). Once > >>>> this program exits at that time another guest is launched in the hos= t and the > >>>> same process is followed. It is continued until the swap is not used= . > >>>> > >>>> 2. 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 > >>>> v11 page hinting - Guest1:23s, Guest2:26s, Guest3:21s swap used =3D = 0 > >>>> v1 bubble hinting - Guest1:23, Guest2:11s, Guest3:26s swap used =3D = 0 > >>>> > >>>> For this particular test-case in a guest which doesn't require swap = access > >>>> "memhog 6G" execution time lies within a range of 15-30s. > >>>> Conclusion - > >>>> In the above test case for an unmodified kernel on executing memhog = in the > >>>> third guest execution time rises to above 2minutes due to swap acces= s. > >>>> Using either page-hinting or bubble hinting brings this execution ti= me to a > >>>> a normal range of 15-30s. > >>> So really this test doesn't add much in value. The whole reason why > >>> Guest3 runs so much slower is because it is going to swap. I initiall= y > >>> did this to demonstrate a point, but now running this test doesn't > >>> prove much as it isn't really meant to be a performance test. It is > >>> essentially just a duplicate of the "how many guests can you run" tes= t > >>> that is passing itself off as some sort of performance test. > >>> > >>> We could probably just drop this from future version of this as long > >>> as we verify that the memory hinting is freeing most of the memory > >>> back and the guest is reporting a size less than the total guest > >>> memory size. > >>> > >> +1, makes sense to keep just one of the above two. > >>>> Setup & procedure - > >>>> Total NUMA Node Memory ~ 15 GB (All guests are run on a single NUMA = node) > >>>> Guest Memory =3D 6GB > >>>> Number of CPUs in the guest =3D 4 > >>>> Process =3D 3 Guests are launched and the =E2=80=98memhog 6G=E2=80= =99 execution time is monitored > >>>> one after the other in each of them. > >>>> Host swap =3D 4GB > >>>> > >>>> Performance Analysis: > >>>> 1. will-it-scale's page_faul1 > >>>> Setup - > >>>> Guest Memory =3D 6GB > >>>> Number of cores =3D 24 > >>>> > >>>> Unmodified kernel - > >>>> 0,0,100,0,100,0 > >>>> 1,514453,95.84,519502,95.83,519502 > >>>> 2,991485,91.67,932268,91.68,1039004 > >>>> 3,1381237,87.36,1264214,87.64,1558506 > >>>> 4,1789116,83.36,1597767,83.88,2078008 > >>>> 5,2181552,79.20,1889489,80.08,2597510 > >>>> 6,2452416,75.05,2001879,77.10,3117012 > >>>> 7,2671047,70.90,2263866,73.22,3636514 > >>>> 8,2930081,66.75,2333813,70.60,4156016 > >>>> 9,3126431,62.60,2370108,68.28,4675518 > >>>> 10,3211937,58.44,2454093,65.74,5195020 > >>>> 11,3162172,54.32,2450822,63.21,5714522 > >>>> 12,3154261,50.14,2272290,58.98,6234024 > >>>> 13,3115174,46.02,2369679,57.74,6753526 > >>>> 14,3150511,41.86,2470837,54.02,7273028 > >>>> 15,3134158,37.71,2428129,51.98,7792530 > >>>> 16,3143067,33.57,2340469,49.54,8312032 > >>>> 17,3112457,29.43,2263627,44.81,8831534 > >>>> 18,3089724,25.29,2181879,38.69,9351036 > >>>> 19,3076878,21.15,2236505,40.01,9870538 > >>>> 20,3091978,16.95,2266327,35.00,10390040 > >>>> 21,3082927,12.84,2172578,28.12,10909542 > >>>> 22,3055282,8.73,2176269,29.14,11429044 > >>>> 23,3081144,4.56,2138442,24.87,11948546 > >>>> 24,3075509,0.45,2173753,21.62,12468048 > >>>> > >>>> page hinting - > >>>> 0,0,100,0,100,0 > >>>> 1,491683,95.83,494366,95.82,494366 > >>>> 2,988415,91.67,919660,91.68,988732 > >>>> 3,1344829,87.52,1244608,87.69,1483098 > >>>> 4,1797933,83.37,1625797,83.70,1977464 > >>>> 5,2179009,79.21,1881534,80.13,2471830 > >>>> 6,2449858,75.07,2078137,76.82,2966196 > >>>> 7,2732122,70.90,2178105,73.75,3460562 > >>>> 8,2910965,66.75,2340901,70.28,3954928 > >>>> 9,3006665,62.61,2353748,67.91,4449294 > >>>> 10,3164752,58.46,2377936,65.08,4943660 > >>>> 11,3234846,54.32,2510149,63.14,5438026 > >>>> 12,3165477,50.17,2412007,59.91,5932392 > >>>> 13,3141457,46.05,2421548,57.85,6426758 > >>>> 14,3135839,41.90,2378021,53.81,6921124 > >>>> 15,3109113,37.75,2269290,51.76,7415490 > >>>> 16,3093613,33.62,2346185,48.73,7909856 > >>>> 17,3086542,29.49,2352140,46.19,8404222 > >>>> 18,3048991,25.36,2217144,41.52,8898588 > >>>> 19,2965500,21.18,2313614,38.18,9392954 > >>>> 20,2928977,17.05,2175316,35.67,9887320 > >>>> 21,2896667,12.91,2141311,28.90,10381686 > >>>> 22,3047782,8.76,2177664,28.24,10876052 > >>>> 23,2994503,4.58,2160976,22.97,11370418 > >>>> 24,3038762,0.47,2053533,22.39,11864784 > >>>> > >>>> bubble-hinting v1 - > >>>> 0,0,100,0,100,0 > >>>> 1,515272,95.83,492355,95.81,515272 > >>>> 2,985903,91.66,919653,91.68,1030544 > >>>> 3,1475300,87.51,1353723,87.65,1545816 > >>>> 4,1783938,83.36,1586307,83.78,2061088 > >>>> 5,2093307,79.20,1867395,79.95,2576360 > >>>> 6,2441370,75.05,2055421,76.65,3091632 > >>>> 7,2650471,70.89,2246014,72.93,3606904 > >>>> 8,2926782,66.75,2333601,70.41,4122176 > >>>> 9,3107617,62.60,2383112,68.46,4637448 > >>>> 10,3192332,58.44,2441626,65.84,5152720 > >>>> 11,3268043,54.32,2235964,62.92,5667992 > >>>> 12,3191105,50.18,2449045,60.49,6183264 > >>>> 13,3145317,46.05,2377317,57.80,6698536 > >>>> 14,3161552,41.91,2395814,53.26,7213808 > >>>> 15,3140443,37.77,2333200,51.42,7729080 > >>>> 16,3130866,33.65,2150967,46.11,8244352 > >>>> 17,3112894,29.52,2372068,45.93,8759624 > >>>> 18,3078424,25.39,2336211,39.85,9274896 > >>>> 19,3036457,21.27,2224821,35.25,9790168 > >>>> 20,3046330,17.13,2199755,37.43,10305440 > >>>> 21,2981130,12.98,2214862,28.67,10820712 > >>>> 22,3017481,8.84,2195996,29.69,11335984 > >>>> 23,2979906,4.68,2173395,25.90,11851256 > >>>> 24,2971170,0.52,2134311,21.89,12366528 > >>> Okay, so this doesn't match up with the results you gave me last time > >>> (https://lore.kernel.org/lkml/afac6f92-74f5-4580-0303-12b7374e5011@re= dhat.com/), > >>> and actually more closely matches what I was expecting to see. The > >>> bubble-hinting patches are performing within a few percent of what th= e > >>> baseline kernel was doing. > >> Interestingly even with an unmodified kernel with every fresh boot, I > >> observed a certain amount of variability in the results which I stated > >> below. > >>> I am assuming the results from before had > >>> some additional debugging enabled for the bubble-hinting test that > >>> wasn't enabled for the other ones. > >> Nope, I had debugging options enabled for all the cases. This time > >> around I disabled all the debug options. > > We can agree to disagree I guess. Those debugging options had reduced > > the throughput by over 30% on the guest kernel in my test runs. I was > > never able to reproduce the data you reported as enabling the same > > debug features on an unmodified kernel had reduced the throughput for > > the test just the same as it did for the bubble hinting version. Were > > you running the debug options on the host kernel or the guest? > In the guest. Do the results which I shared without debug options, match > with what you have? > I am also curious to know if you see any variability in the results of > page_fault1 for an unmodified kernel with every fresh boot? If so how > often? I see some variability, but not much. Usually it can vary by +/- 5% or so. What I have been doing is collecting multiple runs, working out the average, and then comparing that against an average with the patches applied. One other thing you can probably do to limit the variability would be to look at disabling any power management features on the system. One thing you could be seeing is the effect of the CPU enabling turbo mode or going into sleep states if idle. That can easily throw the numbers around quite a bit.