cc Lukasz and Maciej from Intel and changing Dan William's email On 11/21/2012 03:07 PM, Rob Evers wrote:
These patches replace the original t10 type 2 dif mempool implementation by increasing the block and scsi cdb maximum sizes from 16 to 32 bytes. The cdb embedded in the request structure can then be used for type 2 dif commands, or other 32 byte cdbs as required. Motivation for this is that type-2 dif commands should be treated as any other read/writes generally, without any performance penalty. This patch set conflicts with a patch previously posted which addresses a race in UA induced retries with type 2 dif commands. These patches also address that problem: http://marc.info/?l=linux-scsi&m=135186352200668&w=2 Testing: Readily reproduced the race condition panic by simultaneously inducing UAs while load testing 8 scsi_debug devices. With patch applied, same testing ran for 15 hours without a panic. Sanity tested performance using scsi_debug, with and without type 2 dif enabled. Order 80% performance increase noticed with patches when scsi_debug was running in dif type 2 mode. Running scsi_debug without type 2 dif, performance was approximately equal. Used 3.7.0-rc5 for testing and patch generation. root (2): Change the cdb size limits in block and scsi to 32 bytes Change dif type 2 commands to use embedded 32 byte cdb drivers/scsi/sd.c | 45 +-------------------------------------------- drivers/scsi/sd.h | 5 ----- include/linux/blkdev.h | 2 +- include/scsi/scsi_cmnd.h | 13 ++----------- 4 files changed, 4 insertions(+), 61 deletions(-)
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