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    DateThu, 12 May 2005 08:37:57 +0200
    FromJens Axboe <>
    SubjectRe: reducing max segments expected to work?
    On Wed, May 11 2005, Benjamin LaHaise wrote:
    > Hello Jens et al,
    > 
    > Is reducing the max number of segments in the block layer supposed to 
    > work (as done in the patch below), or should i be sticking to mucking 
    > with MAX_PHYS_SEGMENTS?  I seem to get a kernel thatt cannot boot with 
    > the below patch applied, and was wondering if you're aware of any 
    > problems in this area.  I'll probably post something more detailed 
    > tomorrow after trying a few things.
    > 
    > 		-ben
    > -- 
    > "Time is what keeps everything from happening all at once." -- John Wheeler
    > 
    > 
    > diff -purN v2.6.12-rc4/include/linux/blkdev.h test-rc4/include/linux/blkdev.h
    > --- v2.6.12-rc4/include/linux/blkdev.h	2005-04-28 11:02:01.000000000 -0400
    > +++ test-rc4/include/linux/blkdev.h	2005-05-11 17:06:10.000000000 -0400
    > @@ -667,8 +667,8 @@ extern long blk_congestion_wait(int rw, 
    >  extern void blk_rq_bio_prep(request_queue_t *, struct request *, struct bio *);
    >  extern int blkdev_issue_flush(struct block_device *, sector_t *);
    > 
    > -#define MAX_PHYS_SEGMENTS 128
    > -#define MAX_HW_SEGMENTS 128
    > +#define MAX_PHYS_SEGMENTS 32
    > +#define MAX_HW_SEGMENTS 32
    >  #define MAX_SECTORS 255
    
    This doesn't really do what you would think it does - the defines should
    be called DEFAULT_PHYS_SEGMENTS etc, since they are just default values
    and do not denote any max-allowed-by-driver value.
    
    But it is strange why your system wont boot after applying the above.
    What happens (and what kind of storage)?
    
    -- 
    Jens Axboe
    
    -
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