[...] >> Moreover, for reasons brought up while reviewing Adrian's series, >> regarding if mq is "ready", and because I see that the diff for patch >> 12 is small, I suggest that we just skip the step adding a Kconfig >> option to allow an opt-in of the mq path. In other words, *the* patch >> that makes the switch to mq, should also remove the entire left over >> of rubbish code, from the legacy request path. That's also what you do >> in patch12, nice! > > Partly true. > > Adrian also pointed out the rubbishness of the error handling code > in the old stack, and my patch set does *not* fix that. It is also a part > of his patch set I like very much and a reason why I would prefer to > use Adrian's patches if possible. > > We have the following risk factors: > > - Observed performance degradation of 1% (on x86 SDHI I guess)
I don't think that small degradation is a reason for not enabling mq, although for sure we should continue to investigate why it is. > - The kernel crashes if SD card is removed (both patch sets) Yep, this needs to be fixed. > - The risk of something nasty happening we don't know of :-) > >> Finally, I understand that you would be happy to scrap this series, >> but instead let Adrian's series, when re-posted, to go first. Could >> you perhaps re-consider that, because I wonder if it may not be >> smother and less risky, to actually apply everything up to patch 11 in >> this series? > > This is possible. > > But I think it is preferred to proceed with Adrian's patches. > I really like the looks of the code. He says he's coming back with > a set that also kills off the old block layer, and I am pretty > positive I will just ACK the whole thing. Alright, let's go with this option! > > I optimistically think we can jointly fix the card removal issue > and possible also mitigate or root-cause the performance > degradation observed by Adrian > > In the best of worlds, Ming Lei's patches will just fix this too > (we'll see, we can probably get a branch from the block people > to try it) else we can use tracing and perf to drill into it I guess. I think most of Ming's patches addressing performance issues should be in Linus' master already, so once I have a my next branch based on 4.15rc1, we should be able to run a new round of test. Anyway, if anything else is needed from the generic block layer, sure I am open to pull in a branch if needed. > >> I noticed that you reported issues with card removal during I/O (for >> both yours and Adrian's mq patch), but does those problems exists at >> patch 11 - or is those explicitly introduced with the mk patch (patch >> 12)? > > I tested it and it is present earlier in the series. I would have to > revisit and hash it out. Right. So, let's then forget about my suggested approach and spend time more wisely on Adrian's series. > >> Of course, I realize that if we apply everything up to patch11, that >> would require a massive re-base of Adrian's mq/CQE series, but on the >> other hand, then matter which mq patch we decide to go with, it should >> be a rather small diff, thus easy to review and less risky. > > At this point I would prefer to use Adrian's series. He has explained > pretty well his reasoning and when I tested the code it was performing > well. I have some outstanding thingies, but this I can just as well do > on top of his patches. Yep. As stated above, let's go for that solution. I will then be awaiting a new version from Adrian, hopefully I can apply his series already when rc1 is out, to make sure we get enough time to smoke out any remaining problems. Kind regards Uffe
