• Slava Oks's WebLog

    Be aware: To Hyper or not to Hyper

    • 35 Comments
    Our customers observed very interesting behavior on high end Hyperthreading (HT) enabled hardware. They noticed that in some cases when high load is applied SQL Server CPU usage increases significantly but SQL Server performance degrades. Occasionally...
  • Slava Oks's WebLog

    Q & A: Does SQL Server always respond to memory pressure?

    • 8 Comments
    Q: I thought I've seen reference recently to problems with SQL2005 not releasing memory when under pressure, and this was possibly due to the Lock Pages In Memory option. We have a server where this seems to be happening, i.e. SQL2005 uses all available...
  • Slava Oks's WebLog

    SQLOS's memory manager and SQL Server's Buffer Pool

    • 15 Comments
    SQLOS's memory manager consists of several components such as memory nodes, memory clerks, memory caches, and memory objects. Fig 1. depicts memory manager components and their relationship: ---------------- | Memory Object | ---------------- | | V -...
  • Slava Oks's WebLog

    Be Aware: Using AWE, locked pages in memory, on 64 bit

    • 9 Comments
    We have already talked about Windows AWE mechanism on 32 bit and how SQL Server utilizes it. Today I would like to go over AWE & related mechanism on 64 bit platforms. To some people it comes as a surprise that AWE mechanism is still present...
  • Slava Oks's WebLog

    Getting an exception call stack from the catch block (C++)

    • 12 Comments
    This is my first post in this category so I am really looking forward to your comments :-) Today I would like to cover a specific feature related to our implementation of C++ exception handling. Every day I realize that not many people are familiar with...
  • Slava Oks's WebLog

    SQLOS's memory manager: responding to memory pressure

    • 16 Comments
    Resource Monitor and Memory Pressure When configuring SQL Server it is very important to understand how it reacts to memory pressure. I have already spent significant amount of time describing types of memory pressure. In this post you will understand...
  • Slava Oks's WebLog

    Q and A: Using Lock Pages In memory on 64 bit platform

    • 24 Comments
    Q: Hello Slava, I would like to confirm my understanding that on SQL 2005 64 bit edition it is recommended to grant Lock Pages in Memory right to the SQL account and then turn on the AWE setting. Thanks A: Yes, we do recommend to turn on Lock pages...
  • Slava Oks's WebLog

    A look at Windows Virtual Memory mechanisms (continuation of "A look at Virtual Address Space - VAS")

    • 11 Comments
    As I promised last time here comes next post on memory J . Remember, my eventual goal is to reveal how memory management works in SQL Server but for you to really appreciate it, I think, you do need to get good feeling on how Windows manages memory. Understanding...
  • Slava Oks's WebLog

    Memory Pressure - Classified

    • 11 Comments
    So far I touched on subjects that have been widely discussed in the industry. Today I would like to talk about a subject that you would hardly find information about: memory pressure.. On a surface the subject appears simple but in reality this is not...
  • Slava Oks's WebLog

    SQL Server 2005 NUMA support & troubleshooting

    • 4 Comments
    SQL Server 2005 has been designed to take advantage of NUMA features exposed by both hardware and the Windows operating system. There are several caveats that you need to be aware when attempting to run SQL Server on NUMA platforms. In this post...
  • Slava Oks's WebLog

    Q and A: Max memory with sql server 2000 / win2003 x64

    • 3 Comments
    Today, I received following question Q: Slava, I have a question for you. Sql 2000 is documented to support a maximum of 64GB when used with 2000 datacenter edition. I assume this is the limit of 2000 Datacenter, but is it also a limit defined in sql...
  • Slava Oks's WebLog

    Q and A: x64 & AWE mechanism

    • 11 Comments
    Today I received following question: Hello, We will be running Windows Server 2003 x64 with SQL Server 2005 x64. I would think AWE would not come into the picture in this scenario. I'm trying to find out more about SQL Server 2005 memory management...
  • Slava Oks's WebLog

    A look at Virtual Address Space - VAS

    • 7 Comments
    Memory is a set of common resources shared by applications, their components and operating system. One needs to be very specific when referring to a given memory resource. Mistakenly, in many cases, developers, users, DBAs refer to different memory resources...
  • Slava Oks's WebLog

    Changes in dbcc memorystatus in Yukon

    • 6 Comments
    You probably have used dbcc memory status command in SQL2000. In Yukon we have changed output of dbcc memorystatus to reflect new memory manager design, covered in my previous post. The first part of the output represents overall amount of memory consumed...
  • Slava Oks's WebLog

    Q and A: Ratio between AWE Allocated and VM Committed/Reserved in DBCC MEMORYSTATUS output

    • 1 Comments
    Q: What kind of ratio should you expect to see between AWE Allocated and VM Committed/Reserved? We are running 8GB with a cap of 7GB in the max server memory and yet the VM Committed is around 100MB. I was first shocked to see that the sqlservice in task...
  • Slava Oks's WebLog

    SQLOS's DMVs

    • 8 Comments
    SQL Server 2005 has a large number of DMVs that you can take advantage of especially when you try to understand behavioral characteristics of your SQL Server 2005 installation. DMVs expose enormous amount of information but how can you make use of it...
  • Slava Oks's WebLog

    SQLOS's DMVs Continue

    • 6 Comments
    sys.dm_os_schedulers Q. Do I need to by more CPUs? In order to answer this question you have to find out if your load is really CPU bounded. Your load is really CPU bounded if a number of runnable tasks per each scheduler always greater than...
  • Slava Oks's WebLog

    SQLOSDMV's Continue

    • 1 Comments
    sys.dm_os_waiting_tasks One can run lots of interesting queries using this view. You can even use this view to perform deadlock detection that is not resolvable by deadlock monitor, DM. For example if you have tasks waiting on external resources such...
  • Slava Oks's WebLog

    Be Aware: 4GB of VAS under WOW, does it really worth it?

    • 7 Comments
    By now you have heard a lot about the fact that under WOW a 32 bit process can get 4GB of VAS. I agree this is great, but I would like you to be aware of something that might hit you really hard. As it turns out enabling 4GB VAS can be problematic due...
  • Slava Oks's WebLog

    Set of new features in SQL Server 2005 enabled by SQLOS

    • 4 Comments
    Couple of weeks ago I had a chance to visit set of our customers and talk to them directly. It was an unforgettable experience. As a part of the visit I made set of presentations related to SQLOS and new features it enables in SQL Server 2005. I thought...
  • Slava Oks's WebLog

    Q and A: SQL Server memory allocated outside of Buffer Pool, formerly known as MemToLeave

    • 2 Comments
    Q. Under SQL Server 2000 Is the memtoleave concept still valid under 64-bit? A. Yes. If SQL Server’s component requests memory larger than 8 KB block, the block will be allocated outside of Buffer Pool. Remember, inside of SQL Server, Buffer Pool is...
  • Slava Oks's WebLog

    Q and A: Enabling AWE settings for SQL Server 32 bit edition in WOW

    • 1 Comments
    Q. A customer wants to run SQL 2000 SP4 in a Windows Server 2003 SP1 x64 edition. They did the installation without problems but SQL Server is not using more than 4GB of memory. Is it possible to enable AWE in this configuration? A. The answer is yes...
  • Slava Oks's WebLog

    Retrieving information about CPUs' relationships

    • 6 Comments
    In order for server side applications to run efficiently on modern hardware they have to understand hardware layout. As we are moving towards multicore and multi node NUMA systems, understanding relationships amongst cores, logical and physical CPU has...
  • Slava Oks's WebLog

    Configuring SQL Server 2005 for Soft NUMA

    • 6 Comments
    Sometimes I am surprised how issues come up the moment you mention them J . Recently, I have discussed Soft NUMA configurations in the article http://blogs.msdn.com/slavao/articles/441058.aspx . This week one of our customers had an interesting problem...
  • Slava Oks's WebLog

    Q and A: Virtual Address Space, VAS, reservation - why bother?

    • 4 Comments
    Seems like today is a question day :-). I will attempt to answer several questions about VAS I got today: Q1. There is one aspect of Virtual Memory that is just not clear yet. I think I understand about VAS, but maybe not as much as I could, but I...
Page 1 of 2 (45 items) 12