On Fri, 2009-01-23 at 07:03 +0900, FUJITA Tomonori wrote: > So, Boaz, what do you want to do exactly? It should have in the patch > description. I don't want to add something that nobody uses. OK, can we step back a bit from this? Everyone seems to be talking past each other. The original complaint was that multiple commands against the same device issued by SG_IO could be executed "out of order". This is really irrelevant because we never guarantee execution order in the first place. However, if you consider our current at head insertion policy coupled with a multi-threaded application issuing hundreds of SG_IO requests at once, you can see we have a potential starvation issue: Commands at the tail of the queue end up pushed further and further back as more commands are added to the head. This starvation issue is worth addressing, I think, and it can only be addressed by allowing tail insertion. The original reason for at head is, as you surmise, inherited from sg and the rationale is largely for error handling: you need error handling commands to pre-empt everything in the current queue. 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
