cciss: set max scatter gather entries to 32 on P600
At one time we used to set the maximum number of scatter gather elements on all Smart Array controllers to 32. At some point in time the firmware began to write the "appropriate" value for each controller into the config table. The cciss driver would then read that and set h->maxsgentries. h->maxsgentries = readl(&(h->cfgtable->MaxSGElements); On the P600 that value is 544. Under some workloads a significant performance reduction may result. This patch forces the P600 to use only 32 scatter gather elements. Other controllers are not affected. Signed-off-by: NMike Miller <mike.miller@hp.com> Signed-off-by: NDwight (Bud) Brown <bubrown@redhat.com> Signed-off-by: NTomas Henzl <thenzl@redhat.com> Acked-by: NStephen M. Cameron <steve.cameron@hp.com> Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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