Subject: + cciss-set-max-scatter-gather-entries-to-32-on-p600.patch added to -mm tree
To: mike.miller@xxxxxx,axboe@xxxxxxxxx,bubrown@xxxxxxxxxx,steve.cameron@xxxxxx,thenzl@xxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Wed, 14 Aug 2013 14:14:22 -0700
The patch titled
Subject: cciss: set max scatter gather entries to 32 on P600
has been added to the -mm tree. Its filename is
cciss-set-max-scatter-gather-entries-to-32-on-p600.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/cciss-set-max-scatter-gather-entries-to-32-on-p600.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/cciss-set-max-scatter-gather-entries-to-32-on-p600.patch
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From: Mike Miller <mike.miller@xxxxxx>
Subject: 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: Mike Miller <mike.miller@xxxxxx>
Signed-off-by: Dwight (Bud) Brown <bubrown@xxxxxxxxxx>
Signed-off-by: Tomas Henzl <thenzl@xxxxxxxxxx>
Acked-by: Stephen M. Cameron <steve.cameron@xxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/block/cciss.c | 7 +++++++
1 file changed, 7 insertions(+)
diff -puN drivers/block/cciss.c~cciss-set-max-scatter-gather-entries-to-32-on-p600 drivers/block/cciss.c
--- a/drivers/block/cciss.c~cciss-set-max-scatter-gather-entries-to-32-on-p600
+++ a/drivers/block/cciss.c
@@ -4258,6 +4258,13 @@ static void cciss_find_board_params(ctlr
h->nr_cmds = h->max_commands - 4 - cciss_tape_cmds;
h->maxsgentries = readl(&(h->cfgtable->MaxSGElements));
/*
+ * The P600 may exhibit poor performnace under some workloads
+ * if we use the value in the configuration table. Limit this
+ * controller to MAXSGENTRIES (32) instead.
+ */
+ if (h->board_id == 0x3225103C)
+ h->maxsgentries = MAXSGENTRIES;
+ /*
* Limit in-command s/g elements to 32 save dma'able memory.
* Howvever spec says if 0, use 31
*/
_
Patches currently in -mm which might be from mike.miller@xxxxxx are
cciss-set-max-scatter-gather-entries-to-32-on-p600.patch
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