lkml.org 
[lkml]   [1999]   [May]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [patch] checksum P6 asm buffer overflow fix + 686 improvements
    Ingo Molnar wrote:
    >
    > it, smaller chunks are rather common. The performance difference between
    > 64-byte and 128-byte chunks is mostly only visible if everything is fully
    > cached (like in your benchmark). In cold-cache situations it's invisible.
    > The hot-cache benchmark is rather misleading, because according to that
    > benchmark the fastest routine is that is unrolled to handle a whole MTU
    > sized packet. Going from 64 bytes to 128 bytes causes 192 bytes more
    > icache footprint, i dont think this is worth it.

    Just to give some concrete numbers: A fully unrolled (upto 2048bytes)
    csum_partial() does about 5% better than the current stock 686 code for
    1480 sized lenghts. The size of the routine inreases from (iirc - i
    measured this yesterday) 23x bytes to 23xx bytes...
    [note that for short buffers, only a small part of the routine will
    be executed though - so the icache footprint may not be much
    bigger for these cases. still...]


    > doing fast MMX TCP checksums is possible, even if the MMX engine doesnt
    > have a carry logic, this is from a csum routine i wrote a year ago:

    > demonstrates the method nicely), but i finally found that the FPU handling
    > complexity is simply not worth it. More and more networking cards are
    > doing IP checksumming anyway.

    MMX is probably not worth is for the checksum alone, but for
    the checksum&copy case could, maybe, be a win. Is your MMX code
    available somewhere?

    artur


    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.rutgers.edu
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2005-03-22 13:51    [W:5.167 / U:0.008 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site