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    SubjectRe: Kernel 2.6.21.3 does not work with 8GB of RAM on Intel 965WH motherboards.
    Justin Piszcz wrote:
    > Short Description of Problem:
    > Linux 2.6.21.3 does not run properly with 8GB of ram on the Intel 965WH
    > motherboard.
    >
    > Long Description of Problem:
    > When I use 8GB of memory on my x86_64 system, CPU-bound processes are VERY
    > slow, up to 36x slower than usual. My temporary fix is force Linux to only
    > use 4GB of memory, I am currently using mem=4096M. I ran memtest86 and the
    > memory is fine, not a single error. I tried the following to mem= 1024,
    > 2048
    > 4096 and blank "" to let the kernel use all 8GB of memory. What is wrong
    > with the kernel and how come it cannot use 8GB of memory without slowing
    > down
    > all CPU-related processes to a snail-like pace? There is something
    > horribly
    > wrong here.
    >
    > Specifications:
    > Intel Motherboard: 965WH
    > Linux Kernel: 2.6.21.3
    > Distribution: Debian Testing x86_64
    > GCC: gcc version 4.1.2 20061115 (prerelease) (Debian 4.1.1-21)
    > Target: x86_64-linux-gnu
    >
    > Tests:
    >
    > 1. append line = 1024M
    > top - 18:28:26 up 1 min, 4 users, load average: 0.42, 0.17, 0.06
    > Tasks: 157 total, 1 running, 156 sleeping, 0 stopped, 0 zombie
    > Cpu(s): 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si,
    > 0.0%st
    > Mem: 1027016k total, 964288k used, 62728k free, 1232k buffers
    > Swap: 16787768k total, 0k used, 16787768k free, 105168k cached
    > ---> STATUS: No problems, box is fine, no lag, etc..
    >
    > 2. append line = 2048M
    > top - 18:34:23 up 2 min, 2 users, load average: 0.14, 0.14, 0.05
    > Tasks: 147 total, 1 running, 146 sleeping, 0 stopped, 0 zombie
    > Cpu(s): 1.7%us, 1.2%sy, 0.4%ni, 95.2%id, 1.5%wa, 0.0%hi, 0.0%si,
    > 0.0%st
    > Mem: 2059696k total, 956324k used, 1103372k free, 1232k buffers
    > Swap: 16787768k total, 0k used, 16787768k free, 102924k cached
    > ---> STATUS: No problems, box is fine, no lag, etc..
    >
    > 3. append line = 4096M
    > top - 18:37:55 up 1 min, 1 user, load average: 0.52, 0.19, 0.07
    > Tasks: 143 total, 1 running, 142 sleeping, 0 stopped, 0 zombie
    > Cpu(s): 2.9%us, 2.2%sy, 0.7%ni, 91.6%id, 2.6%wa, 0.0%hi, 0.0%si,
    > 0.0%st
    > Mem: 3339536k total, 949792k used, 2389744k free, 1232k buffers
    > Swap: 16787768k total, 0k used, 16787768k free, 99920k cached
    >
    > $ time ssh p34 uptime
    > 19:00:16 up 1 min, 1 user, load average: 0.67, 0.18, 0.06
    > real 0m0.159s
    > user 0m0.013s
    > sys 0m0.003s
    > ---> STATUS: No problems, box is fine, no lag, etc..
    >
    > 4. append line = "" (use all 8GB)
    >
    > top - 18:52:50 up 9 min, 1 user, load average: 2.88, 2.43, 1.41
    > Tasks: 149 total, 3 running, 146 sleeping, 0 stopped, 0 zombie
    > Cpu(s): 36.3%us, 2.2%sy, 10.3%ni, 50.8%id, 0.4%wa, 0.0%hi, 0.1%si,
    > 0.0%st
    > Mem: 8104460k total, 1064416k used, 7040044k free, 3296k buffers
    > Swap: 16787768k total, 0k used, 16787768k free, 201852k cached
    >
    > $ ssh p34
    > ssh: connect to host p34 port 22: Connection refused
    >
    > Machine takes 5-10 minutes to boot, it acts like a 286 computer, about 8
    > minutes later:
    >
    > $ time ssh p34 uptime # 5 SECONDS!! 36x slower when using 8GB of RAM
    > 18:51:39 up 8 min, 1 user, load average: 2.74, 2.31, 1.30
    >
    > real 0m5.757s
    > user 0m0.015s
    > sys 0m0.004s
    >
    > The machine is VERY slow and this is on a gigabit network, I/O does not
    > seem to be affected but rather, CPU-bound processes.
    >
    > PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
    > 2483 root 25 0 25324 5292 1072 R 96 0.1 4:37.12 mailgraph
    > 3604 logcheck 30 10 3408 1120 544 R 91 0.0 0:03.55 grep
    >
    > These normally take seconds but when I use all 8GB of memory, it runs
    > for a very long time.
    >
    > Conclusion: For now, I will be using mem=4096M until someone can help me
    > understand what is happening here. Can anyone offer any insight?
    >
    > I found it interesting in make menuconfig on x86_64 there is no 4GB/64GB
    > options in the kernel that I remember seeing in 32bit.

    That's because that option is not applicable in 64-bit mode.

    Can you send your full dmesg output from the 8GB bootup?

    --
    Robert Hancock Saskatoon, SK, Canada
    To email, remove "nospam" from hancockr@nospamshaw.ca
    Home Page: http://www.roberthancock.com/

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