On Wed, 2009-04-01 at 08:20 -0400, Ross Walker wrote: > On Apr 1, 2009, at 2:29 AM, Bart Van Assche <bart.vanassche@xxxxxxxxx> > wrote: > > > On Tue, Mar 31, 2009 at 8:43 PM, Ross S. W. Walker > > <RWalker@xxxxxxxxxxxxx> wrote: > >> IET just needs to fix how it does it workload with CFQ which > >> somehow SCST has overcome. Of course SCST tweaks the Linux kernel to > >> gain some extra speed. > > > > I'm not familiar with the implementation details of CFQ, but I know > > that one of the changes between SCST 1.0.0 and SCST 1.0.1 is that the > > default number of kernel threads of the scst_vdisk kernel module has > > been increased to 5. Could this explain the performance difference > > between SCST and IET for FILEIO and BLOCKIO ? > > Thank for the update. IET has used 8 threads per target for ages now, > I don't think it is that. > > It may be how the I/O threads are forked in SCST that causes them to > be in the same I/O context with each other. > > I'm pretty sure implementing a version of the patch that was used for > the dump command (found on the LKML) will fix this. > > But thanks goes to Vlad for pointing this dificiency out so we can fix > it to help make IET even better. SCST explicitly fiddles with the io context to get this to happen. It has a hack to block to export alloc_io_context: http://marc.info/?t=122893564800003 James -- To unsubscribe from this list: 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
