On Sat, 1 Apr 2006, Douglas Gilbert wrote: > 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, > >> ... > 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 was able to read 65535 blocks (32 MB - 512 B) for each SCSI command from my disk using the sym53c8xx_2 driver and SG_IO through the sg driverv. I did not change SYM_CONF_MAX but I did add blk_queue_max_segment_size(sdev->request_queue, 256 * 1024); to sym53c8xx_slave_configure to increase the maximum segment size for the queue. Did you do also this? > 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". > The maximum segments size limitation is mentioned on your page. Maybe you emphasize that without changing this you can't get beyond 16 MB with only 128 segments. -- Kai - : 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
