[lkml]   [2002]   [May]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: x86 question: Can a process have > 3GB memory?

    > Huh? Unless you mean ppc64, ppc is worse.
    > On a Mac, you get 2 GB of virtual memory per
    > process. You get up to 512 MB of physical memory
    > without highmem support, or usually 4 GB with
    > highmem support.

    This is fixed in recent kernels, you can specify it with a CONFIG

    # uname -a
    Linux 2.4.19-pre5 #185 Fri Apr 5 14:36:40 EST 2002 ppc

    # cat /proc/self/maps
    0fea5000-0ffbb000 r-xp 00000000 03:0c 163581 /lib/
    0ffbb000-0ffc5000 ---p 00116000 03:0c 163581 /lib/
    0ffc5000-0ffeb000 rw-p 00110000 03:0c 163581 /lib/
    0ffeb000-0fff0000 rw-p 00000000 00:00 0
    10000000-10003000 r-xp 00000000 03:0c 1554092 /bin/cat
    10012000-10013000 rw-p 00002000 03:0c 1554092 /bin/cat
    10013000-10015000 rwxp 00000000 00:00 0
    48000000-48014000 r-xp 00000000 03:0c 163537 /lib/
    48014000-48015000 rw-p 00000000 00:00 0
    48023000-48027000 rw-p 00013000 03:0c 163537 /lib/
    bfffe000-c0000000 rwxp fffff000 00:00 0

    Of course on ppc64 kernels you have a full 4GB of userspace since
    the kernel sits at the top of the 64bit address space.

    > As with x86, the latest chips
    > offer a 36-bit (64 GB) physical address space.

    Paulus also has a hack that allows up to 15G of memory on POWER3 class
    machines although that isnt currently in the ppc32 tree.

    > That's not all! Linus recently singled out the PowerPC
    > MMU for a nice long abusive rant. :-) You get hashed
    > page tables. You get this:
    > As with x86, segment registers map a 32-bit virtual
    > address space onto a larger one. The top 4 bits of
    > a 32-bit virtual address are used to select a segment,
    > and the segment provides 24 more address bits to
    > give you a 52-bit virtual address. Eeeew.

    This is all very well and good, put my ppc64 machine still outperforms
    anything out there on the kernel compile benchmark :)

    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    More majordomo info at
    Please read the FAQ at

     \ /
      Last update: 2005-03-22 13:26    [W:0.026 / U:15.320 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site