On 2005-04-11T08:43:08, Jens Axboe <axboe@xxxxxxx> wrote: > > > In the interest of reducing delay time when testing either good or > > > failed paths, could we (1) prevent SCSI mid-layer initiated i/o > > > retry of these requests and (2) insert the test path i/os at the > > > head of the path's block i/o queue? Doing either of these will > > > require some kernel enhancement since there is no way to > > > either request fail fast capability or insertion at queue head for > > > a SCSI CDB issued from user space. > > > > > > Currently the scsi_cmd_ioctl->sg_io->blk_execute_rq code > > > path for a multipath test i/o does not set the REQ_FAILFAST > > > bit in the flags field of the request structure and unconditionally > > > inserts the request at the tail of the request queue for the scsi > > > device representing the scsi path being tested. > > > > > > Possibly the desire for each of these two attributes could be > > > passed as a flag bit setting in the flag field of the sg_io_hdr > > > structure passed into the kernel as part of the test path ioctl(2). Ed, do you have a patch yet? Sincerely, Lars Marowsky-Brée <lmb@xxxxxxx> -- High Availability & Clustering SUSE Labs, Research and Development SUSE LINUX Products GmbH - A Novell Business