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    SubjectRe: [PATCH] Fake NUMA emulation for PowerPC
    Olof Johansson wrote:
    > Hi,
    >
    > On Sat, Dec 08, 2007 at 02:44:25AM +0530, Balbir Singh wrote:
    >
    >> Comments are as always welcome!
    >
    > Care to explain what this is useful for? (Not saying it's a stupid idea,
    > just wondering what the reason for doing it is).
    >

    In my case, I use it to test parts of my memory controller patches on an
    emulated NUMA machine. I plan to use it to test out page migration
    across nodes.

    >> diff -puN arch/powerpc/mm/numa.c~ppc-fake-numa-easy arch/powerpc/mm/numa.c
    >> --- linux-2.6.24-rc4-mm1/arch/powerpc/mm/numa.c~ppc-fake-numa-easy 2007-12-07 21:25:55.000000000 +0530
    >> +++ linux-2.6.24-rc4-mm1-balbir/arch/powerpc/mm/numa.c 2007-12-08 02:36:02.000000000 +0530
    >> @@ -24,6 +24,8 @@
    >>
    >> static int numa_enabled = 1;
    >>
    >> +char *cmdline __initdata;
    >> +
    >
    > Looks like this should be static.
    >

    Yes, good catch!

    >> @@ -702,6 +744,9 @@ static int __init early_numa(char *p)
    >> if (strstr(p, "debug"))
    >> numa_debug = 1;
    >>
    >> + if (strstr(p, "fake="))
    >> + cmdline = p + 5; /* 5 is faster than strlen("fake=") */
    >
    > This doesn't look right.
    >
    > You check if it contains fake=, not if it starts with it. So if someone
    > did: "numa=foo,fake=bar", or even "numa=debug,fake=", things wouldn't
    > work right.
    >

    Yes, you are right. I merely followed the strstr convention already
    present, which as you righly point out is wrong. I suspect I need to do
    something like

    p = strstr(p, "fake=")
    if (p)
    cmdline = p + 5;

    This would still allow us to do things like

    numa=foo,fake=bar but the memparse() utility would fail at fake=bar
    ^^^

    or even

    numa=debug,fake=1G

    I suspect that this should be good enough for a command line option.

    >
    > -Olof


    --
    Thanks,
    Balbir Singh
    Linux Technology Center
    IBM, ISTL


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