From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Return-Path: Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 12.0 \(3445.100.39\)) Subject: Re: [PATCH 00/12] unify the interface of the proportional-share policy in blkio/io From: Paolo Valente In-Reply-To: <20181112095632.69114-1-paolo.valente@linaro.org> Date: Mon, 12 Nov 2018 10:58:29 +0100 Cc: linux-block , linux-kernel , Ulf Hansson , Linus Walleij , Mark Brown , 'Paolo Valente' via bfq-iosched , Oleksandr Natalenko , cgroups@vger.kernel.org, linux-doc@vger.kernel.org, Jonathan Corbet , lennart@poettering.net Message-Id: References: <20181112095632.69114-1-paolo.valente@linaro.org> To: Jens Axboe , Greg Kroah-Hartman , Tejun Heo , Li Zefan , Angelo Ruocco , Dennis Zhou , Josef Bacik , Liu Bo , Bart Van Assche , Johannes Weiner List-ID: Forgot to CC Lennart, sorry. > Il giorno 12 nov 2018, alle ore 10:56, Paolo Valente = ha scritto: >=20 > Hi Jens, Tejun, all, > about nine months ago, we agreed on a solution for unifying the > interface of the proportional-share policy in blkio/io [1]. Angelo > and I finally completed it. Let me briefly recall the problem and the > solution. >=20 > The current implementation of cgroups doesn't allow two or more > entities, e.g., I/O schedulers, to share the same files. So, if CFQ > creates its files for the proportional-share policy, such as, e.g, > weight files for blkio/io groups, BFQ cannot attach somehow to them. > Thus, to enable people to set group weights with BFQ, I resorted to > making BFQ create its own version of these common files, by prepending > a bfq prefix. >=20 > Actually, no legacy code uses these different names, or is likely to > do so. Having these two sets of names is simply a source of > confusion, as pointed out also, e.g., by Lennart Poettering (CCed > here), and acknowledged by Tejun [2]. >=20 > In [1] we agreed on a solution that solves this problem, by actually > making it possible to share cgroups files. Both writing to and > reading from a shared file trigger the appropriate operation for each > of the entities that share the file. In particular, in case of > reading, > - if all entities produce the same output, the this common output is > shown only once; > - if the outputs differ, then every per-entity output is shown, > preceded by the name of the entity that produced that output. >=20 > With this solution, legacy code that, e.g., sets group weights, just > works, regardless of the I/O scheduler actually implementing > proportional share. >=20 > But note that this extension is not restricted to only blkio/io. The > general group interface now enables files to be shared among multiple > entities of any kind. >=20 > (I have also added a patch to fix some clerical errors in bfq doc, > which I found while making the latter consistent with the new > interface.) >=20 > Thanks, > Paolo >=20 > [1] https://lkml.org/lkml/2018/1/4/667 > [2] https://github.com/systemd/systemd/issues/7057 >=20 > Angelo Ruocco (7): > kernfs: add function to find kernfs_node without increasing ref > counter > cgroup: link cftypes of the same subsystem with the same name > cgroup: add owner name to cftypes > block, bfq: align min and default weights with cfq > cgroup: make all functions of all cftypes be invoked > block, cfq: allow cgroup files to be shared > block, throttle: allow sharing cgroup statistic files >=20 > Paolo Valente (5): > cgroup: add hook seq_show_cft with also the owning cftype as = parameter > block, cgroup: pass cftype to functions that need to use it > block, bfq: use standard file names for the proportional-share policy > doc, bfq-iosched: fix a few clerical errors > doc, bfq-iosched: make it consistent with the new cgroup interface >=20 > Documentation/block/bfq-iosched.txt | 31 +++-- > block/bfq-cgroup.c | 148 +++++++++++++------- > block/bfq-iosched.h | 4 +- > block/blk-cgroup.c | 22 +-- > block/blk-throttle.c | 24 ++-- > block/cfq-iosched.c | 105 +++++++++++---- > fs/kernfs/dir.c | 13 ++ > include/linux/blk-cgroup.h | 10 +- > include/linux/cgroup-defs.h | 14 +- > include/linux/cgroup.h | 13 ++ > include/linux/kernfs.h | 7 + > kernel/cgroup/cgroup.c | 262 = +++++++++++++++++++++++++++++------- > 12 files changed, 483 insertions(+), 170 deletions(-) >=20 > -- > 2.16.1