On 4/8/19 9:06 AM, Paolo Valente wrote: > > >> Il giorno 8 apr 2019, alle ore 17:05, Jens Axboe <axboe@xxxxxxxxx> ha scritto: >> >> On 4/8/19 9:04 AM, Johannes Thumshirn wrote: >>> [+Cc Michal ] >>> On Mon, Apr 08, 2019 at 04:54:39PM +0200, Paolo Valente wrote: >>>> >>>> >>>>> Il giorno 8 apr 2019, alle ore 16:49, Johannes Thumshirn <jthumshirn@xxxxxxx> ha scritto: >>>>> >>>>> On Mon, Apr 08, 2019 at 04:39:35PM +0200, Paolo Valente wrote: >>>>>> From: Angelo Ruocco <angeloruocco90@xxxxxxxxx> >>>>>> >>>>>> When bfq was merged into mainline, there were two I/O schedulers that >>>>>> implemented the proportional-share policy: bfq for blk-mq and cfq for >>>>>> legacy blk. bfq's interface files in the blkio/io controller have the >>>>>> same names as cfq. But the cgroups interface doesn't allow two >>>>>> entities to use the same name for their files, so for bfq we had to >>>>>> prepend the "bfq" prefix to each of its files. However no legacy code >>>>>> uses these modified file names. This naming also causes confusion, as, >>>>>> e.g., in [1]. >>>>>> >>>>>> Now cfq has gone with legacy blk, so there is no need any longer for >>>>>> these prefixes in (the never used) bfq names. In view of this fact, this >>>>>> commit removes these prefixes, thereby enabling legacy code to truly >>>>>> use the proportional share policy in blk-mq. >>>>>> >>>>>> [1] https://github.com/systemd/systemd/issues/7057 >>>>> >>>>> Hmm, but isn't this a user-space facing interface and thus some sort of ABI? >>>>> Do you know what's using it and what breaks due to this conversion? >>>>> >>>> >>>> Yep, but AFAIK, the problem is exactly the opposite: nobody uses these >>>> names for the proportional-share policy, or wants to use these names. I'm >>>> CCing Lennart too, in case he has some improbable news on this. >>>> >>>> So the idea is to align names to what people expect, possibly before >>>> more confusion arises. >>> >>> OK, crazy idea, not sure if Jens and Tejun will beat me for this, but >>> symlinks? >>> >>> This way we can a) keep the old files and b) have them point to the new (a.k.a >>> cfq style) files. >> >> I did consider that, and that would be doable. But honestly, I'm having a >> hard time seeing what issue we are attempting to fix by doing this. >> > > The problem is ~100% of people and software believing to set weights and not doing it. I'm sorry, but I don't know what that means? -- Jens Axboe
