Kai Makisara wrote: > On Tue, 28 Mar 2006, Matthew Wilcox wrote: > > >>This patch enables clustering and sets max_sectors to 0xffff to enable >>reading and writing of large blocks with tapes (and large transfers with >>sg). This change is needed after the sg and st drivers started using >>chained bios through scsi_request_async() in 2.6.16. >> >>Signed-off-by: Kai Makisara <kai.makisara@xxxxxxxxxxx> >>Signed-off-by: Matthew Wilcox <matthew@xxxxxx> >> >>--- >> >> drivers/scsi/sym53c8xx_2/sym_glue.c | 3 ++- >> 1 files changed, 2 insertions(+), 1 deletions(-) >> >>1c573ec4648b4b4ddadcbd1945a9a608977df513 >>diff --git a/drivers/scsi/sym53c8xx_2/sym_glue.c b/drivers/scsi/sym53c8xx_2/sym_glue.c >>index e48409e..2c4e5f1 100644 >>--- a/drivers/scsi/sym53c8xx_2/sym_glue.c >>+++ b/drivers/scsi/sym53c8xx_2/sym_glue.c >>@@ -1870,7 +1870,8 @@ static struct scsi_host_template sym2_te >> .eh_bus_reset_handler = sym53c8xx_eh_bus_reset_handler, >> .eh_host_reset_handler = sym53c8xx_eh_host_reset_handler, >> .this_id = 7, >>- .use_clustering = DISABLE_CLUSTERING, >>+ .use_clustering = ENABLE_CLUSTERING, >>+ .max_sectors = 0xFFFF, >> #ifdef SYM_LINUX_PROC_INFO_SUPPORT >> .proc_info = sym53c8xx_proc_info, >> .proc_name = NAME53C8XX, >> > > Did you approve this patch or just forgot to remove it from the queue > after the discussion initiated by Jens Axboe? > > I have done some more investigation based on the message from Gerard > Roudier that Jens found. I fetched the FreeBSD driver. It had a > work-around for the 896 rev. 1 chips but I did not find that in the Linux > version. The work-around does build two device s/g elements for any > original s/g segment that crosses a 16 MB boundary. Kai + Matthew, In my testing with lk 2.6.16 the 16 MB boundary is a hard limit, after several other things are tweaked. The sym53c8xx driver won't even come close due to: #define SYM_CONF_MAX_SG (96) ... instance->sg_tablesize = SYM_CONF_MAX_SG; I assume that the st driver (like sg) limits on .sg_tablesize . Matthew, if you change this please set it at 256 (not SG_ALL which is 255). I have attempted to capture the current (overly complex) constraints on maximum transfer size at: http://www.torque.net/sg/sg_io.html in the section on "Maximum transfer size per command". > In Linux we can do that by setting the .dma_boundary field in the > scsi_host_template. Would it be an acceptable solution to set the 16 MB > limit for all sym53c8xx adapters? It would take care of the known errata > and Gerards suspicions about possible problems with other chips. > > The patch at the end does compile and it is running in this system but has > not had any more testing. Doug Gilbert - : send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
