Hi Werner! Am Montag, 12. September 2011 schrieb Werner Fischer: > On Don, 2011-09-08 at 14:39 +0200, Jens Axboe wrote: > > On 2011-09-05 16:01, Werner Fischer wrote: > > > On Don, 2011-09-01 at 15:13 -0600, Jens Axboe wrote: > > >> [...] > > >> I mean that every device should plug in at the same place. There are > > >> definite up and down sides to plugging in at the stacking level and > > >> bypassing the IO scheduler. So you have to weight the pros and cons > > >> before doing that. We need to fix this. Drivers doing that lose out on > > >> other features in the name of a bit more performance, that's just not > > >> acceptable. > > > > > > I have updated the diagram according to all of your hints: > > > http://www.thomas-krenn.com/de/wikiDE/images/0/07/Linux-IO-Stack.png > > > > > > I had also some off-list discussion with Florian Haas, who convinced me > > > that the file systems are below of the page cache. I hope this is now > > > correct. > > > > Not sure I'd agree with that, I'd place the page cache between the fs > > and the storage layer. > > After some further off-list feedback from Christoph Hellwig I did some > updates on the block diagram, including moving the page cache from above > the fs layer to next to the fs layer (Christoph told me that the page > cache is a helper function for the file systems). > I also added SCSI mid layer, SCSI low layer, libata and so on: > http://www.thomas-krenn.com/de/wikiDE/images/0/07/Linux-IO-Stack.png > > I'm looking forward to further feedback. Not that I would like to use it, but where would dmraid sit? I think it would be a bit nearer to the SCSI low layer... I am not quite used to the placement of the page cache, but if its merely a helper function for filesystems... Regarding performance measurements it makes a lot of difference. I think the current diagram hides the impact of using pagecache or not using it a bit. So maybe at least coloring it differently would give it a bit more visual weight. Aside from that I find this very detailed and I learned quite a bit from just looking at it. Can you make that image available as SVG too? Thanks, -- Martin Steigerwald - teamix GmbH - http://www.teamix.de gpg: 19E3 8D42 896F D004 08AC A0CA 1E10 C593 0399 AE90 -- To unsubscribe from this list: send the line "unsubscribe fio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
