Messages in this thread | | | Date | Thu, 24 Jul 2008 11:07:02 -0400 (EDT) | From | Mikulas Patocka <> | Subject | Re: [PATCH] block: fix q->max_segment_size checking in blk_recalc_rq_segments about VMERGE |
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> > For a dumb I/O card, you advertise SG_ALL capabilities, the IOMMU > > is going to merge things as it would have anyways, and you have > > code in the driver to advance SG entries after each "dumb I/O". > > Not that dumb ... they just have a limited number of SG slots. We > wouldn't want to run them as spoon fed PIO because that really would > kill performance. > > > There is zero value to the vmerge code, the real gains are being > > realized already. > > There is value to me in my testbed, which I can't achieve any other way > (except by buying different SCSI cards). > > As I said, you can compile it out on sparc just fine. I wish to keep it > running for parisc, so I'll maintain it. If it ever bit rots out of > parisc like it has done for the other architectures, then feel free to > remove it. > > James
So try to #define BIO_VMERGE_BOUNDARY 0 for Pa-Risc and tell us what performance degradation do you see (and what driver do you use and what is the I/O pattern).
If you show something specific, we can consider that --- but you haven't yet told us anything, except generic talk.
Mikulas
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