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    SubjectRe: cciss update for 2.4.24-pre1, #3
    Marcelo,
    Prefetch has undergone extensive testing internally. Other groups are
    continuing to test it, also. All controllers on the street now have
    prefetch enabled. When version 1.92 of the controller f/w is released
    prefetch will be disabled by default. This patch re-enables it on x86 only
    because of a _big_ performance hit in RAID1 operations.
    This is on my list for 2.6. Since it has now been released I will begin
    submitting updates after Christmas. (My list for 2.6 is extensive.)
    Also, please include this version of the patch rather than my first
    submission. I moved a variable inside the ifdef to clean up warnings on
    non-x86 platforms.

    Thanks,
    mikem
    mike.miller@hp.com
    ------------------------------------------------------------------------------
    diff -burN lx2424pre1.test2/drivers/block/cciss.c lx2424pre1.test/drivers/block/cciss.c
    --- lx2424pre1.test2/drivers/block/cciss.c 2003-12-18 09:12:52.000000000 -0600
    +++ lx2424pre1.test/drivers/block/cciss.c 2003-12-18 09:09:11.000000000 -0600
    @@ -2675,6 +2675,15 @@
    printk("Does not appear to be a valid CISS config table\n");
    return -1;
    }
    +
    +#ifdef CONFIG_X86
    + /* Need to enable prefetch in the SCSI core for 6400 in x86 */
    + __u32 prefetch;
    + prefetch = readl(&(c->cfgtable->SCSI_Prefetch));
    + prefetch |= 0x100;
    + writel(prefetch, &(c->cfgtable->SCSI_Prefetch));
    +#endif
    +
    #ifdef CCISS_DEBUG
    printk("Trying to put board into Simple mode\n");
    #endif /* CCISS_DEBUG */
    diff -burN lx2424pre1.test2/drivers/block/cciss_cmd.h lx2424pre1.test/drivers/block/cciss_cmd.h
    --- lx2424pre1.test2/drivers/block/cciss_cmd.h 2003-06-13 09:51:32.000000000 -0500
    +++ lx2424pre1.test/drivers/block/cciss_cmd.h 2003-12-18 09:10:01.000000000 -0600
    @@ -266,6 +266,7 @@
    DWORD Reserved;
    BYTE ServerName[16];
    DWORD HeartBeat;
    + DWORD SCSI_Prefetch;
    } CfgTable_struct;
    #pragma pack()
    #endif /* CCISS_CMD_H */
    -------------------------------------------------------------------------------
    On Fri, 19 Dec 2003, Marcelo Tosatti wrote:
    >
    >
    > On Wed, 17 Dec 2003 mikem@beardog.cca.cpqcorp.net wrote:
    >
    > > Sorry I forgot to send this fix in with the 2 patches I submitted
    > > yesterday. We found a bug in the ASIC used on the 64xx Smart Array
    > > controllers. When prefetching from host memory we grab an extra 750 or
    > > so bytes of data. If this occurs on a memory boundary the machine will crash.
    > > This is primarily an issue on IPF and Alpha systems although it could happen
    > > on other platforms. Proliant systems are not affected by this bug because
    > > memory is contiguous and the top 4k of memory is masked off by the system
    > > firmware. The solution to the problem is to disable SCSI prefetch in the
    > > controller firmware. This results in a performance hit on x86 during RAID1
    > > operations. This patch turns on prefetch for x86 based systems only.
    > > Please consider this patch for inclusion in the 2.4.24 kernel.
    > > This patch should be applied after the 2 I submitted yesterday. It will
    > > patch into a fresh tree with offsets.
    >
    > The other two patches have been included.
    >
    > Has the prefetching been tested for long? Which kernels have it enabled?
    >
    > What about 2.6?
    >
    -
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