Re: [PATCH V3 00/11] block-throttle: add .high limit

From	Vivek Goyal <vgoyal@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH V3 00/11] block-throttle: add .high limit
Date	2016-10-06 20:40 +0200
Message-ID	<splKh-4z5-1@gated-at.bofh.it> (permalink)
References	(5 earlier) <spbKV-5wA-3@gated-at.bofh.it> <spbKV-5wA-1@gated-at.bofh.it> <spgKC-A6-27@gated-at.bofh.it> <spkXT-3Nc-9@gated-at.bofh.it> <splhf-4du-1@gated-at.bofh.it>
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On Thu, Oct 06, 2016 at 08:01:42PM +0200, Paolo Valente wrote:
> 
> > Il giorno 06 ott 2016, alle ore 19:49, Vivek Goyal <vgoyal@redhat.com> ha scritto:
> > 
> > On Thu, Oct 06, 2016 at 03:15:50PM +0200, Paolo Valente wrote:
> > 
> > [..]
> >> Shaohua, I have just realized that I have unconsciously defended a
> >> wrong argument.  Although all the facts that I have reported are
> >> evidently true, I have argued as if the question was: "do we need to
> >> throw away throttling because there is proportional, or do we need to
> >> throw away proportional share because there is throttling?".  This
> >> question is simply wrong, as I think consciously (sorry for my
> >> dissociated behavior :) ).
> > 
> > I was wondering about the same. We need both and both should be able 
> > to work with fast devices of today using blk-mq interfaces without
> > much overhead.
> > 
> >> 
> >> The best goal to achieve is to have both a good throttling mechanism,
> >> and a good proportional share scheduler.  This goal would be valid if
> >> even if there was just one important scenario for each of the two
> >> approaches.  The vulnus here is that you guys are constantly, and
> >> rightly, working on solutions to achieve and consolidate reasonable
> >> QoS guarantees, but an apparently very good proportional-share
> >> scheduler has been kept off for years.  If you (or others) have good
> >> arguments to support this state of affairs, then this would probably
> >> be an important point to discuss.
> > 
> > Paolo, CFQ is legacy now and if we can come up with a proportional
> > IO mechanism which works reasonably well with fast devices using
> > blk-mq interfaces, that will be much more interesting.
> > 
> 
> That's absolutely true.  But, why do we pretend not to know that, for
> (at least) hundreds of thousands of users Linux will go on giving bad
> responsiveness, starvation, high latency and unfairness, until blk
> will not be used any more (assuming that these problems will somehow
> disappear will blk-mq).  Many of these users are fully aware of these
> Linux long-standing problems.  We could solve these problems by just
> adding a scheduler that has already been adopted, and thus extensively
> tested, by thousands of users.  And more and more people are aware of
> this fact too.  Are we doing the right thing?

Hi Paolo,

People have been using CFQ for many years. I am not sure if benefits 
offered by BFQ over CFQ are significant enough to justify taking a
completely new code and get rid of CFQ. Or are the benfits significant
enough that one feels like putting time and effort into this and
take chances wiht new code.

At this point of time replacing CFQ with something better is not a
priority for me. But if something better and stable goes upstream, I
will gladly use it.

Vivek

Thread

[PATCH V3 00/11] block-throttle: add .high limit Shaohua Li <shli@fb.com> - 2016-10-03 23:30 +0200
  [PATCH v3 10/11] block-throttle: add a simple idle detection Shaohua Li <shli@fb.com> - 2016-10-03 23:30 +0200
  [PATCH v3 07/11] blk-throttle: make throtl_slice tunable Shaohua Li <shli@fb.com> - 2016-10-03 23:30 +0200
  [PATCH v3 08/11] blk-throttle: detect completed idle cgroup Shaohua Li <shli@fb.com> - 2016-10-03 23:30 +0200
  [PATCH v3 06/11] blk-throttle: make sure expire time isn't too big Shaohua Li <shli@fb.com> - 2016-10-03 23:30 +0200
  [PATCH v3 11/11] blk-throttle: ignore idle cgroup limit Shaohua Li <shli@fb.com> - 2016-10-03 23:30 +0200
  [PATCH v3 09/11] block-throttle: make bandwidth change smooth Shaohua Li <shli@fb.com> - 2016-10-03 23:30 +0200
  [PATCH v3 03/11] block-throttle: configure bps/iops limit for cgroup in high limit Shaohua Li <shli@fb.com> - 2016-10-03 23:30 +0200
  [PATCH v3 01/11] block-throttle: prepare support multiple limits Shaohua Li <shli@fb.com> - 2016-10-03 23:30 +0200
  [PATCH v3 02/11] block-throttle: add .high interface Shaohua Li <shli@fb.com> - 2016-10-03 23:30 +0200
  Re: [PATCH V3 00/11] block-throttle: add .high limit Vivek Goyal <vgoyal@redhat.com> - 2016-10-04 15:30 +0200
    Re: [PATCH V3 00/11] block-throttle: add .high limit Tejun Heo <tj@kernel.org> - 2016-10-04 18:00 +0200
      Re: [PATCH V3 00/11] block-throttle: add .high limit Tejun Heo <tj@kernel.org> - 2016-10-04 18:30 +0200
        Re: [PATCH V3 00/11] block-throttle: add .high limit Paolo Valente <paolo.valente@unimore.it> - 2016-10-04 19:10 +0200
          Re: [PATCH V3 00/11] block-throttle: add .high limit Paolo Valente <paolo.valente@unimore.it> - 2016-10-04 19:50 +0200
            Re: [PATCH V3 00/11] block-throttle: add .high limit Tejun Heo <tj@kernel.org> - 2016-10-04 21:00 +0200
              Re: [PATCH V3 00/11] block-throttle: add .high limit Paolo Valente <paolo.valente@unimore.it> - 2016-10-04 21:10 +0200
                Re: [PATCH V3 00/11] block-throttle: add .high limit Tejun Heo <tj@kernel.org> - 2016-10-04 21:20 +0200
                Re: [PATCH V3 00/11] block-throttle: add .high limit Paolo Valente <paolo.valente@unimore.it> - 2016-10-04 21:40 +0200
                Re: [PATCH V3 00/11] block-throttle: add .high limit Tejun Heo <tj@kernel.org> - 2016-10-04 22:30 +0200
                Re: [PATCH V3 00/11] block-throttle: add .high limit Paolo Valente <paolo.valente@unimore.it> - 2016-10-05 14:40 +0200
                Re: [PATCH V3 00/11] block-throttle: add .high limit Vivek Goyal <vgoyal@redhat.com> - 2016-10-05 15:20 +0200
                Re: [PATCH V3 00/11] block-throttle: add .high limit Paolo Valente <paolo.valente@unimore.it> - 2016-10-05 16:10 +0200
                Re: [PATCH V3 00/11] block-throttle: add .high limit Tejun Heo <tj@kernel.org> - 2016-10-05 17:00 +0200
                Re: [PATCH V3 00/11] block-throttle: add .high limit Paolo Valente <paolo.valente@unimore.it> - 2016-10-05 21:50 +0200
                Re: [PATCH V3 00/11] block-throttle: add .high limit Paolo Valente <paolo.valente@unimore.it> - 2016-10-05 22:10 +0200
                Re: [PATCH V3 00/11] block-throttle: add .high limit Paolo Valente <paolo.valente@unimore.it> - 2016-10-06 10:00 +0200
                Re: [PATCH V3 00/11] block-throttle: add .high limit Paolo Valente <paolo.valente@unimore.it> - 2016-10-06 15:20 +0200
                Re: [PATCH V3 00/11] block-throttle: add .high limit Vivek Goyal <vgoyal@redhat.com> - 2016-10-06 19:50 +0200
                Re: [PATCH V3 00/11] block-throttle: add .high limit Paolo Valente <paolo.valente@unimore.it> - 2016-10-06 20:10 +0200
                Re: [PATCH V3 00/11] block-throttle: add .high limit Vivek Goyal <vgoyal@redhat.com> - 2016-10-06 20:40 +0200
                Re: [PATCH V3 00/11] block-throttle: add .high limit Paolo Valente <paolo.valente@unimore.it> - 2016-10-06 23:00 +0200
                Re: [PATCH V3 00/11] block-throttle: add .high limit Mark Brown <broonie@kernel.org> - 2016-10-06 21:50 +0200
                Re: [PATCH V3 00/11] block-throttle: add .high limit Paolo Valente <paolo.valente@unimore.it> - 2016-10-07 00:30 +0200
                Re: [PATCH V3 00/11] block-throttle: add .high limit Paolo Valente <paolo.valente@unimore.it> - 2016-10-05 22:00 +0200
                Re: [PATCH V3 00/11] block-throttle: add .high limit Paolo Valente <paolo.valente@unimore.it> - 2016-10-06 09:30 +0200
                Fwd: [PATCH V3 00/11] block-throttle: add .high limit Kyle Sanderson <kyle.leet@gmail.com> - 2016-10-09 03:20 +0200
                Re: [PATCH V3 00/11] block-throttle: add .high limit Linus Walleij <linus.walleij@linaro.org> - 2016-10-06 10:10 +0200
                Re: [PATCH V3 00/11] block-throttle: add .high limit Mark Brown <broonie@kernel.org> - 2016-10-06 13:10 +0200
                Re: [PATCH V3 00/11] block-throttle: add .high limit "Austin S. Hemmelgarn" <ahferroin7@gmail.com> - 2016-10-06 14:00 +0200
                Re: [PATCH V3 00/11] block-throttle: add .high limit Paolo Valente <paolo.valente@unimore.it> - 2016-10-06 15:00 +0200
                Re: [PATCH V3 00/11] block-throttle: add .high limit "Austin S. Hemmelgarn" <ahferroin7@gmail.com> - 2016-10-06 16:00 +0200
                Re: [PATCH V3 00/11] block-throttle: add .high limit Paolo Valente <paolo.valente@unimore.it> - 2016-10-06 17:10 +0200
                Re: [PATCH V3 00/11] block-throttle: add .high limit "Austin S. Hemmelgarn" <ahferroin7@gmail.com> - 2016-10-06 17:20 +0200
                Re: [PATCH V3 00/11] block-throttle: add .high limit Heinz Diehl <htd+ml@fritha.org> - 2016-10-08 12:50 +0200
            Re: [PATCH V3 00/11] block-throttle: add .high limit Paolo Valente <paolo.valente@unimore.it> - 2016-10-04 21:50 +0200
      Re: [PATCH V3 00/11] block-throttle: add .high limit Paolo Valente <paolo.valente@unimore.it> - 2016-10-04 18:30 +0200
      Re: [PATCH V3 00/11] block-throttle: add .high limit Vivek Goyal <vgoyal@redhat.com> - 2016-10-04 20:20 +0200
        Re: [PATCH V3 00/11] block-throttle: add .high limit Tejun Heo <tj@kernel.org> - 2016-10-04 21:00 +0200
          Re: [PATCH V3 00/11] block-throttle: add .high limit Paolo Valente <paolo.valente@unimore.it> - 2016-10-04 21:00 +0200

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