Hi all, some months ago I asked several questions regarding the design of the Linux I/O stack. Thank you all for your feedback you gave. * We have now drawn the Linux I/O Stack diagram with Inkscape, to have it in svg format and nicer pdf/png's. * We have licensed it under CC-BY-SA 3.0, so everybody can use and alter it when necessary * I have also included some feedback I got from James Bottomley and Hannes Reinecke at LinuxCon Europe in Prague * Here is the link to the first published version (version 0.1): http://www.thomas-krenn.com/en/oss/linux-io-stack-diagram.html Can you take a look at it and send us feedback in case there are some errors left in the diagram? Best regards, Werner On Die, 2011-09-27 at 16:06 +0200, Martin Steigerwald wrote: > 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, -- : Werner Fischer : Technology Specialist : Thomas-Krenn.AG | The server-experts : http://www.thomas-krenn.com | http://www.thomas-krenn.com/wiki -- 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
