On Fri, Feb 26, 2016 at 12:00 PM, Andy Grover <agrover@xxxxxxxxxx> wrote: > On 02/26/2016 11:43 AM, Sheng Yang wrote: >>> >>> I thought we could allocate an exactly 1MB buffer, with your changes, no? >>> That warning message may need to be changed. >> >> >> Yes we can, it make sense to remove the warning message. >> >> Though I am not quite comfortable with one request fill the whole >> buffer, because we would only able to handle one request with the >> whole ring. >> >> Like we discussed in >> http://comments.gmane.org/gmane.linux.scsi.target.devel/11107 , we >> should have a ring buffer fits all requests from upper layer. > > > I still don't have a good answer for what we should do here. If we want to > accommodate 1MB requests, and we want to have a reasonable queue depth (64? > 128?) then we would be vmalloc()ing more than 64MB for each TCMU device. > That seems too wasteful to me. I think in that case we don't want to handle 1MB request. We can limit the max sectors one command can handle to e.g. 128 sectors/64kb, then 128 commands in queue, so that's 8M for data ring, which sound pretty reasonable. The problem is I don't know how to limit it on TCMU. I can only find a way to do it in tcm loopback device. --Sheng > > -- Andy > -- To unsubscribe from this list: send the line "unsubscribe target-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
