Thursday, July 21, 2016

Major Linux I/O Bug? SPOLER: No


Alternate title: Betteridge's Law Holds!

Last week, I posted on what I thought was an I/O bug in RHEL 7 and CentOS 7. I've now done enough testing to eliminate this possibility.  So, as promised:


So what was happening, then, that led me to get such drastically different results?

First, and most importantly, as I noted in an update to the prior post, one system was using SSD and the other was using spinning disk.  That accounted for the large bulk of the difference.  It still leaves the somewhat unsolved mystery of my production performance problems that coincided roughly in time with when the OS was updated (which is what led me down that rabbit hole in the first place).

But there may also have been other configuration changes made around that time that accounted for this.  In preliminary testing, I've found that I get better performance by turning kernel asynchronous I/O off, contrary to conventional wisdom (and to what I've found on other platforms). I've coupled this with also disabling DIRECT_IO, though I believe the latter may be a bad thing: it may be that the performance is buoyed by caching that's going on at the OS level, which would mean that data hasn't really been committed to disk even though the DB engine believes that it has. By making these two changes, I've gotten the performance on the production system back close to previous (good) levels, at least for the time being.

But anyway, false alarm, and egg on my face.


59 comments:

  1. Replies
    1. IEEE Final Year projects Project Center in Chennai are consistently sought after. Final Year Students Projects take a shot at them to improve their aptitudes, while specialists like the enjoyment in interfering with innovation. For experts, it's an alternate ball game through and through. Smaller than expected IEEE Final Year project centers ground for all fragments of CSE & IT engineers hoping to assemble. <Final Year Projects for CSE It gives you tips and rules that is progressively critical to consider while choosing any final year project point.

      JavaScript Training in Chennai

      JavaScript Training in Chennai

      The Angular Training covers a wide range of topics including Components, project projects for cseAngular Directives, Angular Services, Pipes, security fundamentals, Routing, and Angular programmability. The new Angular TRaining will lay the foundation you need to specialise in Single Page Application developer. Angular Training

      Delete
  2. Hi, I am really happy to found such a helpful and fascinating post that is written in well manner. Thanks for sharing such an informative post. keep update your blog. R Programming Online Training

    ReplyDelete
  3. I read your blog.It was informative I am getting conglomerations of info’s about Dotnet certification. Thanks for sharing; I would like to see your updates regularly so keep blogging.
    Regards,
    Dot Net Training in Chennai
    Android Training in Chennai
    Selenium Training in Chennai
    Hadoop Training in Chennai

    ReplyDelete
  4. Interesting post! This is really helpful for me. I like it! Thanks for sharing!
    Mobile application developers in Chennai | PHP developers Chennai

    ReplyDelete
  5. This is an awesome post. Really very informative and creative contents. This concept is a good way to enhance the knowledge. Excellent post.
    java training in chennai
    java course in chennai

    ReplyDelete
  6. Home Mart is a site about Home Improvement, Furniture, Home Appliances and many more.
    Check out the best
    furniture sale
    Dog Cages
    bedroom furniture nz
    entertainment unit

    ReplyDelete
  7. This comment has been removed by the author.

    ReplyDelete
  8. Great blog thanks for sharing Looking for the best creative agency to fuel new brand ideas? Adhuntt Media is not just a digital marketing company in chennai. We specialize in revamping your brand identity to drive in best traffic that converts.

    ReplyDelete
  9. Nice blog thanks for sharing Growing your own plant comes with its own challenges and responsibilities. This is why you need a plant nursery in chennai who is ready to help you out throughout the way and guide you through the hurdles of growing a plant - Enter Karuna Nursery Gardens.

    ReplyDelete
  10. Excellent blog thanks for sharing Pixies Beauty Shop is unlike any of the other cosmetic shops in Chennai. With tons of exclusive imported brands to choose from and the best value, this is the best shopping destination for your personal and salon needs.

    ReplyDelete
  11. Awesome blog thanks for sharing While choosing your perfect ride for driving, Accord Cars comes with and the best packages for you to pick from. Self drive cars in Chennai are done the easier. Just pick out your plan from hourly, daily, weekly and even monthly plans available.

    ReplyDelete
  12. Very useful blog thanks for sharing Pearls beauty lounge is the best beauty parlour in chennai. More than 30+ years experience in this field. When you come over at Pearl’s you don’t visit a just a beauty lounge, you are welcomed into an indulging experience which you’ll want to feel again and again. Our secret ingredient for your happiness is in going an extra mile to make you feel pampered.

    ReplyDelete
  13. Awesome blog thankks for sharing 100% virgin Remy Hair Extension in USA, importing from India. Premium and original human hair without joints and bondings. Available in Wigs, Frontal, Wavy, Closure, Bundle, Curly, straight and customized color hairstyles Extensions.

    ReplyDelete
  14. Very useful blog thanks for sharing IndPac India the German technology Packaging and sealing machines in India is the leading manufacturer and exporter of Packing Machines in India.

    ReplyDelete
  15. It is amazing and wonderful to visit your site.Thanks for sharing this information,this is useful to me...
    http://chennaitraining.in/oracle-training-in-chennai/
    http://chennaitraining.in/oracle-dba-training-in-chennai/
    http://chennaitraining.in/odi-training-in-chennai/
    http://chennaitraining.in/oracle-soa-training-in-chennai/
    http://chennaitraining.in/teradata-training-in-chennai/
    http://chennaitraining.in/informix-training-in-chennai/
    http://chennaitraining.in/sybase-training-in-chennai/
    http://chennaitraining.in/sql-server-dba-training-in-chennai/

    ReplyDelete
  16. Thanks for sharing this informative blog, Nice post and Information Please guys keep it up and share with us some unique post in the future   we are also Mobile app development company in Bangalore, India

    ReplyDelete
  17. Thanks for sharing this informative blog, Nice post and Information Please guys keep it up and share with us some unique post in the future   we are also Mobile app development company in Bangalore, India

    ReplyDelete
  18. Wow what a Great Information about World Day its exceptionally pleasant educational post. a debt of gratitude is in order for the post. VCA cursus

    ReplyDelete
  19. Best Corporate Video Production Company in Bangalore and top Explainer Video Company in Bangalore , 3d, 2d Animation Video Makers in Chennai.
    Many many thanks for sharing such valuable tips. we really appreciate your nice explanation.

    ReplyDelete
  20. This is a nice post in an interesting line of content.Thanks for sharing this article, great way of bring this topic to discussion.

    awesome post presented by you..your writing style is fabulous and keep update with your blogs.
    Mobile App Development Company in Bangalore
    Mobile App Development Companies in Mumbai
    Mobile App Development Company in Delhi
    Top Mobile App Development Companies in Chennai

    ReplyDelete
  21. شرکت تلکا هاست پیشرو در میزبانی انواع وب سایت و هم چنین دارای انواع خرید هاست ارزان با کنترل پنل سی پنل میباشد.حتما از سایت ما دیدن کنید و از قیمت های مناسب برای انواع سرویس های وب و ثبت انواع دامنه شگفت زده شوید.

     

    سایت موسیقی ایرانی دارای محتوای آموزشی اخبار به روز هنر و سینما و موسیقی دانلود فیلم های جدید ایرانی و آموزش ردومی های ایرانی

    ReplyDelete
  22. This is a very nice article we consider your effort of collecting the information and putting it in words as amazing also take a look at our services

    Best mobile app development companies in India
    Best ios app development companies in New Delhi

    ReplyDelete
  23. This is a very good article and nice collection of information , would love to read more of such blogs and also know our services
    Mobile application development in India
    Mobile application development in Dubai
    Mobile application development in Bangalore

    ReplyDelete
  24. Good Post! , it was so good to read and useful to improve my knowledge as an updated one, keep blogging.After seeing your article I want to say that also a well-written article with some very good information which is very useful for the readers....thanks for sharing it and do share more posts likethis. https://www.3ritechnologies.com/course/angular-js-training-institute-in-pune/

    ReplyDelete
  25. Good Post! it was so good to read and useful to improve my knowledge as an updated one, keep blogging. After seeing your article I want to say that also a well-written article with some very good information which is very useful for the readers....thanks for sharing it and do share more posts like this.
    AWS Training

    ReplyDelete
  26. Crypto-currency as a modern form of the digital asset has received a worldwide acclaim for easy and faster financial transactions and its awareness among people have allowed them to take more interest in the field thus opening up new and advanced ways of making payments. Crypto.com Referral Code with the growing demand of this global phenomenon more,new traders and business owners are now willing to invest in this currency platform despite its fluctuating prices however it is quite difficult to choose the best one when the market is full. In the list of crypto-currencies bit-coins is one of the oldest and more popular Crypto.com Referral Code for the last few years. It is basically used for trading goods and services and has become the part of the so-called computerized block-chain system allowing anyone to use it thus increasing the craze among the public, Crypto.com Referral Code.

    Common people who are willing to purchase BTC can use an online wallet system for buying them safely in exchange of cash or credit cards and in a comfortable way from the thousands of BTC foundations around the world and keep them as assets for the future. Due to its popularity, many corporate investors are now accepting them as cross-border payments and the rise is unstoppable. With the advent of the internet and mobile devices,information gathering has become quite easy as a result the BTC financial transactions are accessible and its price is set in accordance with people’s choice and preferences thus leading to a profitable investment with Crypto.com Referral Code Code. Recent surveys have also proved that instability is good for BTC exchange as if there is instability and political unrest in the country due to which banks suffer then investing in BTC can surely be a better option. Again bit-coin transaction fees are pretty cheaper and a more convenient technology for making contracts thus attracting the crowd. The BTC can also be converted into different fiat currencies and is used for trading of securities, for land titles, document stamping, public rewards and vice versa.

    Another advanced block-chain project is Ethereumor the ETH which has served much more than just a digital form of crypto-currency Crypto.com Referral Code and its popularity in the last few decades have allowed billions of people to hold wallets for them. With the ease of the online world,the ETH have allowed the retailers and business organizations to accept them for trading purposes, therefore, can serve as the future of the financial system.

    ReplyDelete
  27. Our full Lace Front Wigs are all hand made with a lace cap. They are manufactured with thin lace sewn on top of the cap. Individual hairs are then sewn onto the thin lace. Each lace wig has lace all around the unit which will need to be cut prior to securing the wig to your head. You will need to cut along the hairline around your entire head. By doing so, you will be able to wear your hair anyway you like. You can even style ponytails, up-dos, etc. Once the Lace Wigs is successfully applied, it will appear that all the hair is growing directly from your head!

    Lace front wigs are hand-made with lace front cap & machine weft at back. Lace front wigs are manufactured with a thin lace that extends from ear to ear across the hairline. When you receive the wig, the lace will be quite long in the front. Cut and style according to your preference, as you will need to apply adhesive along the front of the wig. Once the wig is applied, you will still have Lace Wigs with a very natural appearance.
    TeamWigz Provide the Best Lace Front Wigs and Lace Wigs in Johannesburg and South Africa.

    ReplyDelete
  28. 우리카지노 에 오신 것을 환영합니다. 국내 최고의 카지노사이트 에 가입하여 바카라사이트 에서 다양한 게임을 즐기시면서 대박의 기회를 놓치지마세요! 우리 카지노는 한국의 바카라 산업을 지배하는 카지노 사이트입니다. 우리 카지노는 한국 바카라 시장 점유율의 50 % 이상을 차지하는 10 년 이상 온라인 바카라 시장을 지배 해 왔기 때문에 우리 카지노를 모르는 사람은 거의 없습니다.

    ARTICLE: 우리카지노는 대한민국의 바카라 업계를 장악하고 있는 카지노사이트 입니다. 우리카지노가 대한 민국에서 장악한 바카라 시장점유율이 50%가 넘고 10년 넘게 온라인 바카라 시장을 장악해왔기 때문에 대한민국에서는 우리카지노를 모르는 사람은 드뭅니다. 이런 바카라 업계의 독보적인 입지 때문에 늘 유명하거나 최고만을 찾는 사람들이 카지노사이트를 찾을때는 늘 우리카지노를 찾습니다.바카라를 처음 시작하시는 초보자분들에게도 우리카지노에서 카지노사이트를 시작하시기 좋은 환경입니다. 우리카지노사이트에서는 신규가입시 3만쿠폰을 지급 해주기 때문입니다. 사람들이 늘 1등만을 찾는 이유는 분명 있습니다. 다른 카지노사이트와는 달리 우리카지노를 이용하실시 에이전트를 끼고 게임을 하신다면 본사 이외에 활동쿠폰 및 오링쿠폰을 별도로 제공해주고 있기 때문입니다. 이러한 이유들 때문에 카지노사이트 업계에서 바카라를 즐기신다면 다들 우리카지노를 선호 하십니다. 카지노사이트에서 바카라를 이기기 물론 어렵습니다. 하지만 우리카지노의 에이전트를 끼고 바카라를 즐기신다면 승산이 있다고 봅니다. 우리카지노 에이전트의 연락처는 홈페이지로 연락하시면 언제든지 부담없이 소통가능 합니다. 카지노사이트를 선정할때는 바카라를 다른곳보다 유리하게 즐길 수 있는 카지노를 선택해야한다고 생각합니다. 그것이 바로 우리카지노 입니다. 이상으로 우리카지노와 바카라 카지노사이트 사이의 상관관계를 알아보았습니다바카라사이트.

    ReplyDelete
  29. BUY EMAIL LEADS
    If your company is in the look-out for investors or new business endeavours, business opportunity leads provide you information of those wanting to start a business. They are an email away from being a buyer or your business partner.Time is of the essence in every marketing strategy. Direct mail, for example, purchase email lists takes an extended time from the campaign period to implementation. Not all companies can afford to spend such amount of time to get marketing results. This may be one of the reasons why email marketing became popular. Thanks to modernization and high technology, with your email contact list, you can reach and convey your message to thousands of people with just a few clicks away.

    ReplyDelete
  30. Internet Download Manager 6.38 Build 10 IDM Crack Patch with Serial Crucial down load is a sort of shareware downloadmanager possessed by an American company called Tonec Inc.. IDM Patch Free Download captures any type of download in a extraordinary time limit and completes the download at a very brief time and at a faster speed as compared to any download manager right now. IDM company is based in nyc. This computer program is readily designed for Windows OS just for now.
    Presently IDM Serial Crucial Free has turned into a renowned application with over 20 million clients around the globe. Internet download manager Hack may take downloads from many browsers like Internet Explorer, Microsoft Edge, IDM Crack with Serial Key Google Chrome, Opera, Firefox for practically just about any kind of record of user's choice. It has gained control over down load; nevertheless, it shows its dialog box to an individual.

    ReplyDelete
  31. Tongkat Ali ist eine Pflanze beheimatet in Südostasien. Sie gehört zur Gattung der Bittereschengewächse und Ihr botanischer Name lautet “Eurycoma longifolia”. Es gibt noch eine weitere Reihe länderspezifischer Namen
    wie z. B. “Pasak Bumi”, wie die Pflanze in Indonesien genannt wird oder “longjack”, die allgemeine Bezeichnung für Tongkat Ali Kaufen in den USA, Kanada und Australien.

    Das Ursprungsland von Tongkat Ali Kaufen ist Indonesien, daher findet man auch dort auch die größten Bestände. Weitere Vorkommen gibt es in Ländern wie Thailand, Malaysia, Vietnam und Laos.

    Die Einnahme von Tongkat Ali Kaufen empfiehlt sich insbesondere für Leistungssportler, die einen schnellen
    Muskelaufbau und Muskelzuwachs anstreben und nicht auf illegale und künstliche Substanzen zurückgreifen möchten um Ihren Testosteronspiegel zu erhöhen.

    Generell empfiehlt sich eine Einnahme von Tongkat Ali für alle Männer ab dem 30ten Lebensjahr, da in dieser Phase nachweislich die Produktion von körpereigenem Testosteron zurückgeht. Dies macht sich vor allem dadurch bemerkbar dass die körperliche Leistungsfähigkeit nachlässt, die Lust auf Sex spürbar abnimmt und dadurch allgemein das Selbstwertgefühl negativ beeinflusst wird.

    Mit der Einnahme von Tongkat Ali können Sie nachweislich Ihre Libido steigern, Ihr Testosteron erhöhen und Ihre gewohnte Lebensenergie aus den jungen Jahren Ihres Lebens wieder herbeiführen. Hier können Sie übrigens weitere Informationen bekommen zum Thema ‘Libido steigern‘ ganz natürlich. Sollten Sie daran interessiert sein lohnt es sich auch unseren Artikel über Butea Superba zu lesen.

    Tongkat Ali wächst als Strauch und kann Höhen von bis zu 12 Metern erreichen. Typischerweise dauert es 10-15 Jahre bis solche Ausmaße erreicht werden. Der Strauch trägt anfangs grüne Blüten die sich im Laufe der Zeit, bis zur Reife, rot färben.

    Allerdings sind die Blüten im Hinblick auf die Wirkung der Pflanze weniger interessant. Der wertvolle Teil verbirgt sich unter der Erde.
    Im Laufe der Jahre wachsen die Wurzeln teilweise senkrecht und bis zu mehrere Meter tief in den Boden, was die Ernte zu einer schweren und mühsamen Arbeit werden lässt. Je älter die Wurzeln sind, desto höher ist auch die Anzahl der Wirkstoffe Butea Superba.
    Von daher gilt es einige Dinge zu beachten sollten Sie Tongkat Ali Kaufen wollen.

    ReplyDelete
  32. yellow pages in Dubai has business listings, phone numbers, maps, email addresses and websites for local businesses in Dubai to help you get the job do.

    ReplyDelete
  33. ChemLab Store Store provide you with top quaility research chemicals like: A-pvp, Methylone Crystals, Methylone Powder, Pentedrone Crystals, Pentedrone Powder, MDPV Powder, Buphedrone Powder, 4-FMC Powder, 4-MemABP Powder, NEB Powder, AMT Powder, 6-APB Pellets, Butylone Powder, MDAI Powder, 4-FA Powder, 4-FA Crystals, MPA Powder, Methoxetamine, JWH-122 Powder, JWH-122 Herbal Buds, Ketamine, AM-2201, Herbal Buds, We have a wide range of products including JWH-018, JWH-073, JWH-200, buy 34 dmmc online JWH-250, 4-MEC, 5-IAI, Phenazepam, 2c-i, Actavis Promethazine, Naphyrone, U-47700. Methedrone, crystal meth and other chemicals in all different amounts ranging from 5gm to 1kg retail and also large amounts at wholesale prices, When you buy Research Chemicals or bath salts from us you are guaranteed of the highest quality available on the market, high purity products, secure payment, fast and discreet international delivery.

    Disclaimer: None of the Products on ChemLab Research Chem Store are intended for human consumption and Neither ChemLab Research Chem Store,

    nor any of the staff INCLUDING the owner of ChemLab Online Chem Store resume ANY responsibility for ANY injuries to ANY individual who does not correspond with this warning and will not be held accountable for any loss or damages due to an individual burning, inhaling, or consuming into the body of any human being, animal or living specimen. This statement applies to all of the products sold on this site.

    By purchasing ANY PRODUCT ON THIS SITE, You Agree to be held 100% liable for any personal injury or damages due to you (Customer) using any of the products in any way other than that manufacturer’s instructions of use printed on the package!

    ReplyDelete
  34. Recently, the keto diet has become extremely popular for its health benefits such as weight loss and preventing disease. A custom Keto plan for life! Visit: diet soda on keto

    ReplyDelete
  35. Health Experts have proven that regular exercise coupled with a good diet allow you to live longer and healthier. In this busy day and age, not everyone has the time to go to the gym - resulting to a lot of overweight people that desperately need to exercise. A healthy alternative is for you to Buy Home Gym Equipments that you can store in your own home or even at your office. Here are some tips when buying home gym equipment.

    First, know your fitness goals and keep these goals in mind when you are buying home gym equipment. One of the biggest mistakes that people make is buying the biggest or trendiest fitness machine simply because they like how it looks. More often than not, these end up gathering dust in your storage rooms or garage because you never end up using them. It is important to take note of what particular type of physical activity you want or enjoy doing before you buy your exercise machine. If you are looking to loose a few pounds and you enjoy walking or hiking, a treadmill is the best option for you. If you are looking to tone your lower body while burning calories a stationary bike is your obvious choice. Similarly, Special Equipments for Core Strength Exercises, Strength Training Weight Vests, Core Strength & Abdominal Trainers, Home Cardio Training, Strength Training Power Cages, Strength Training Racks & More.

    Second, set aside a budget before Buying Home Gym Equipments. Quality exercise machines do not come cheap. They are constantly exposed to wear and tear when they are used properly. So, pick machines that are built to last and have passed quality certifications to get the most out of your money. If you are operating on a tight budget, think about investing in several weights, We can Provide you High Quality Home Gym Equipments at Very Low Prices for your Complete Uses: Core Strength Exercises, Strength Training Weight Vests, Core Strength & Abdominal Trainers, Home Cardio Training, Strength Training Power Cages, Strength Training Racks & More.

    Its the Right Time to Buy Home Gym Equipments for you at Very Low Prices.

    ReplyDelete
  36. - Como organizar sua Semana com o Taskade - Segunda Feira, primeiro dia.
    - Como organizar sua semana com o Taskade - Terça - Vlog de Produtividade
    - Como organizar sua semana com o Taskade - Quarta
    Como organizar sua semana com o Taskade - Quinta - Vlog Produtividade.
    - Taskade - Sexta, Sábado e Domingo. Como foi e uma grande novidade

    ReplyDelete
  37. Buy Dank Now began as an idea to create a top-notch delivery service for buy weed online in the US and quickly evolved in much more. Even though California accepted Safe to Buy Marijuana Online in 1996, we felt there was still a major lacking in quality and service. From what once started as a humble, flower-child type movement, evolved into the next California gold rush.

    Buy Dank Now Shop is committed to ensuring that your privacy and security is protected at all times, in fact, we care so much that we offer guaranteed stealth delivery to anywhere in the world at no extra cost! Buy Weed Online, Glo Carts, Glo Extracts, Glo Cart, Glo Cartridges, Glo thc Carts, Glo vape, Lions Breath Carts, Big Chief Carts and All orders are fully guaranteed, so whatever happens, nothing will ever stand between you and your weed!

    With literally thousands upon thousands of amazing strains from the best breeders in the world, ranging from famous cup-winners to potent, CBD-laden medical strains, High THC powerhouses, Glo Extracts, famous cheese to Buy Marijuana Online and Glo Carts popular white widow strains, all the way through to some of the rarest, hardest-to-find varieties in the world.

    Why Is Marijuana Effective for Treating Anxiety? Conventional medicine uses several different kinds of drugs to treat anxiety disorders, including serotonin reuptake inhibitors like Zoloft and tranquilizers like Valium. However, many patients don’t respond well to these medications. One of the non-psychoactive cannabinoids found in marijuana that is commonly used to treat anxiety is cannabidiol (CBD). Various scientists and researchers have experimented with both animals and humans to test the effectiveness of CBD for anxiety treatment.

    You can get it all right here at Buy Dank Now! Because we only ever work with breeders who meet our rigorous quality standards, you can be sure that whatever products you get from our Website such as, Glo Carts, Glo Extracts, Glo Cart, Glo Cartridges, Glo thc Carts, Glo vape, Lions Breath Carts, Big Chief Carts, they’ll make exceptional additions to your genetic library!

    ReplyDelete
  38. PMP certification is the globally recognized certification for project management. It is the validity given by the PMI Institute to candidates who clear certain education and professional criteria - Pass PMP.

    There are many ways to Pass PMP certification.

    [img]https://i.imgur.com/qh9wn8G.png[/img]


    Go for the heavy books, memorize them, sit for PMP trainings on your weekend, sit in the long, sleepy PMP video on demand trainings and still have the unsurety of passing the exam.
    Get PMP dumps, PMP practice exams, PMP review material and try to memorize hundreds of questions and still fear of forgetting some and getting new questions as PMP changes very frequently.
    Contact CBTproxy and through PMP proxy exam, get your PMP certification without any hassle.
    There are several sites selling PMP dumps and PMP exam questions which are 90% not reliable. Since there are always new questions in PMP exam, there is no reliability on the PMP dumps. Contact CBTproxy and through our PMP proxy exam, Pass PMP Certification without any hassle. We ensure first time passing guarantee and liberate the candidate from taking the real exam multiple times - PMP Brain Dump.

    ReplyDelete