On Tue, 2005-12-27 at 08:53 +0900, FUJITA Tomonori wrote: > Mike and I have worked on the tgt mmap version. > > o It does read/write commands like sg by using mmap in user space and > get_user_pages in kernel space. > > o It does non-read/write commands like direct I/O by allocating > aligned buffers in user space and using get_user_pages in kernel space. > > It works like the simple tap that you suggested. It does not allocate > buffers in kernel space at all and does zero copy on all sorts of > commands. > > Here are some performance results with open-iscsi (which are better > than the previous results that I got with sfnet). > > o IET > > | 2005/12/27-07:50:59 | STAT | 6827 | v1.2.8 | /dev/sdc | Total write throughput: 53790310.4B/s (51.30MB/s), IOPS 6566.2/s. > > o current tgt (I/O in kernel space) > > | 2005/12/27-08:07:50 | STAT | 7294 | v1.2.8 | /dev/sdc | Total write throughput: 49666457.6B/s (47.37MB/s), IOPS 6062.8/s. > > o tgt mmap > > | 2005/12/27-08:42:51 | STAT | 5286 | v1.2.8 | /dev/sdc | Total write > throughput: 44701286.4B/s (42.63MB/s), IOPS 5456.7/s. > > We can get something like this if we avoid calling mmap/munmap per > command (by using some sorts of caching). > > o tgt mmap (mmap caching) > > | 2005/12/27-07:53:19 | STAT | 6996 | v1.2.8 | /dev/sdc | Total write throughput: 48253337.6B/s (46.02MB/s), IOPS 5890.3/s. > > > James, can we get your approval of the this mmap design? Yes, that looks fine ... it runs in user space, which was really all I was looking for. There is another half to this, which is that I'd like the tap to come via a SCSI API. This isn't strictly necessary for iSCSI but it would allow us to integrate a generic target approach that could work for all SCSI HBA's as well as just iSCSI. Thanks, James - : 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
