On Mon, 16 Feb 2009 12:29:06 +0200 Boaz Harrosh <bharrosh@xxxxxxxxxxx> wrote: > >>>> exofs is not the first and only file system who is using bios. Proof of > >>>> the matter is that block exports a bio submit routine. > >>> Seems that exofs just passes pages and the ULD sends a SCSI command > >>> including these pages. I don't see how exofs needs to handle bio > >>> directly. > >>> > >> How do you propose to collect these pages? and keep them without allocating > >> an extra list? without pre-allocating a struct request? and without re-inventing > >> the bio structure? > > > > I don't think that allocating an extra list (or something) to keep > > them hurts performance. We can talk about it when you have the real > > performance results. > > So you are the one that starts to invent the wheel here. I thought I was > the one that does that, only you only called me by names, because you never showed > me where. > > But please only answer one question for me: Please don't write back if you do not > answer this question: > > Why do other filesystems allow to use bios? are they going to stop? Who is going > to remove that? Can you stop the argument, "exofs is similar to the existing traditional file systems hence it should be treated equally". It's simply untrue. Does anyone except for panasas people insist the same argument? We are talking about the design of exofs, which also affects the design of OSD ULD (including the library) living in SCSI mid-layer. It's something completely different from existing traditional file systems that work nicely on the top of the block layer. As discussed in another thread, now OSD ULD reinvents the bio handling infrastructure because of the design of exofs. But OSD ULD can use the block layer helper functions to avoid the re-invention if we change the exofs design to take pages instead of bios. For now, it works perfectly for exofs. In the future, we might change it but we don't know until you submit patches (or the performance results) that show taking pages doesn't work for exofs nicely. I guess that we need to evolve the block layer to support OSD stuff cleanly than we've discussed recently. But again we can do when we definitely need to do. -- 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
