| Subject: How much memory allocated to kernel? |
| Group: microsoft.public.winternals |
| Date: 12/12/2007 9:23:12 AM |
| From: Megan Kielman [Email Address Protection] |
I have often heard examples of a system with 4GB where 2GB allocated to user mode and 2GB allocated to kernel mode. Is memory always divided this way? If I had a system with 2GB of memory would 1GB be allocated to user mode and 1GB allocated to Kernel? |
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| Subject: Re: How much memory allocated to kernel? |
| Group: microsoft.public.winternals |
| Date: 12/12/2007 9:28:27 AM |
| From: "JS" [Email Address Protection] |
A description of the 4 GB RAM Tuning feature and the Physical Address Extension switch http://support.microsoft.com/kb/291988/en-us JS "Megan Kielman" <megan.kielman@gmail.com> wrote in message news:OhzmLtNPIHA.4684@TK2MSFTNGP06.phx.gbl... >I have often heard examples of a system with 4GB where 2GB allocated to >user mode and 2GB allocated to kernel mode. Is memory always divided this >way? If I had a system with 2GB of memory would 1GB be allocated to user >mode and 1GB allocated to Kernel? |
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| Subject: Re: How much memory allocated to kernel? |
| Group: microsoft.public.winternals |
| Date: 12/12/2007 11:07:37 AM |
| From: "Ben Voigt [C++ MVP]" [Email Address Protection] |
"Megan Kielman" <megan.kielman@gmail.com> wrote in message news:OhzmLtNPIHA.4684@TK2MSFTNGP06.phx.gbl... >I have often heard examples of a system with 4GB where 2GB allocated to >user mode and 2GB allocated to kernel mode. Is memory always divided this >way? If I had a system with 2GB of memory would 1GB be allocated to user >mode and 1GB allocated to Kernel? No. You are confusing allocation of physical RAM with allocation of address space. There is always 4GB of address space on a 32-bit OS, no matter what the total physical RAM is. |
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| Subject: Re: How much memory allocated to kernel? |
| Group: microsoft.public.winternals |
| Date: 12/13/2007 11:58:22 AM |
| From: Megan Kielman [Email Address Protection] |
Ok but if there is 4GB of address space and only 2GB of RAM, how is that distrubuted amongst the address space? Obviously there isn't enough RAM to use up all the address space. Does the kernel always get 1/2 of physical RAM? Ben Voigt [C++ MVP] wrote: > "Megan Kielman" <megan.kielman@gmail.com> wrote in message > news:OhzmLtNPIHA.4684@TK2MSFTNGP06.phx.gbl... >> I have often heard examples of a system with 4GB where 2GB allocated to >> user mode and 2GB allocated to kernel mode. Is memory always divided this >> way? If I had a system with 2GB of memory would 1GB be allocated to user >> mode and 1GB allocated to Kernel? > > No. > > You are confusing allocation of physical RAM with allocation of address > space. > > There is always 4GB of address space on a 32-bit OS, no matter what the > total physical RAM is. > > |
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| Subject: Re: How much memory allocated to kernel? |
| Group: microsoft.public.winternals |
| Date: 12/13/2007 12:37:42 PM |
| From: "David Craig" [Email Address Protection] |
Read "Windows Internals Windows Server 2003, Windows XP, and Windows 2000 Fourth Edition" by Russinovich and Solomon. This is a fairly simple concept common to mainframe computers for decades. Understanding how it is implemented is more complex with having to know how the OS does it management, "Windows Internals" and how the processor supports the OS's memory management logic. Intel's Processor Documentation is available for free and the various parts show instructions, processor interrupts, optimized coding techniques, and how the various registers, tables, and instructions work to together to provide segments and page tables. Edge cases where the OS is running with minimal memory, such as XP Pro on a 256MB system, may have special code in the OS that causes it to vary from the 'ideal' modes described in the book, but most of the time running with insufficient memory will cause the OS to crash. This may become a consideration when video memory is shared from the base memory available. Since the BIOS commits that memory before the OS obtains control, the machine can appear to the OS to have sufficient memory, but in reality it might be inadequate. My rule is 2GB minimum for XP and just go with 4GB for Vista if it is not just a test system. I think Longhorn Server (Server 2008) should have 8GB or more to run more than a test server. Just running FTP can be done in a lot less memory, but running SQL server requires memory maxed out to obtain desirable throughput.. "Megan Kielman" <megan.kielman@gmail.com> wrote in message news:%23KuHjobPIHA.4476@TK2MSFTNGP06.phx.gbl... > Ok but if there is 4GB of address space and only 2GB of RAM, how is that > distrubuted amongst the address space? Obviously there isn't enough RAM to > use up all the address space. Does the kernel always get 1/2 of physical > RAM? > > Ben Voigt [C++ MVP] wrote: >> "Megan Kielman" <megan.kielman@gmail.com> wrote in message >> news:OhzmLtNPIHA.4684@TK2MSFTNGP06.phx.gbl... >>> I have often heard examples of a system with 4GB where 2GB allocated to >>> user mode and 2GB allocated to kernel mode. Is memory always divided >>> this way? If I had a system with 2GB of memory would 1GB be allocated to >>> user mode and 1GB allocated to Kernel? >> >> No. >> >> You are confusing allocation of physical RAM with allocation of address >> space. >> >> There is always 4GB of address space on a 32-bit OS, no matter what the >> total physical RAM is. |
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