From: Paolo <paolo.valente@linaro.org>
To: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>,
Fabio Checconi <fchecconi@gmail.com>,
Arianna Avanzini <avanzini.arianna@gmail.com>,
linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
ulf.hansson@linaro.org, linus.walleij@linaro.org,
broonie@kernel.org, Jeff Moyer <jmoyer@redhat.com>
Subject: Re: [PATCH RFC 10/22] block, bfq: add full hierarchical scheduling and cgroups support
Date: Thu, 12 May 2016 15:11:42 +0200 [thread overview]
Message-ID: <5734810E.3060001@linaro.org> (raw)
In-Reply-To: <2D83ACA0-2513-4019-9A0D-3166FDDE7485@linaro.org>
Il 06/05/2016 22:20, Paolo Valente ha scritto:
>
> ...
>
> I can now confirm that, because of a little bug, a fraction ranging
> from one third to half of the writeback bios for the writer is wrongly
> associated with the root group. I'm sending a bugfix.
>
> I'm retesting BFQ after this blk fix. If I understand correctly, now
> you agree that BFQ is well suited for cgroups too, at least in
> principle. So I will apply all your suggestions and corrections, and
> submit a fresh patchset.
>
Hi,
this is just to report another apparently important blkio malfunction
(unless what I describe below is, for some reason, normal). This time
the malfunction is related to CFQ.
Even after applying my fix for bio cloning, CFQ may fail to guarantee
the expected resource-time sharing. It happens, for example, in the
following simple scenario with one sequential writer, in a group, and
one sequential reader, in another group. Both groups have the same
weight (and are memory.high limited to 16MB). Yet the writer is served
for only about 4% of the time, instead of 50%. Its bw is consequently
very low. Being this an unwanted accident, this percentage probably
varies with the characteristics of the system at hand.
The causes of the problem seem to be buried in CFQ logic, and do not
seem trivial. So I guess that solving this problem is not worth the
effort, as BFQ seems to have hope to replace CFQ altogether. I'm then
focusing on BFQ: it suffers from a similar problem, but because of a
rather simple reason.
Thanks,
Paolo
> Thanks,
> Paolo
>
>> Ok (if there is some quick way to get this information without
>> instrumenting the code, then any suggestion or pointer is welcome).
>>
>> Thanks,
>> Paolo
>>
>>> Thanks.
>
next prev parent reply other threads:[~2016-05-12 13:11 UTC|newest]
Thread overview: 103+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-01 22:12 [PATCH RFC 00/22] Replace the CFQ I/O Scheduler with BFQ Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 01/22] block, cfq: remove queue merging for close cooperators Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 02/22] block, cfq: remove close-based preemption Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 03/22] block, cfq: remove deep seek queues logic Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 04/22] block, cfq: remove SSD-related logic Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 05/22] block, cfq: get rid of hierarchical support Paolo Valente
2016-02-10 23:04 ` Tejun Heo
2016-02-01 22:12 ` [PATCH RFC 06/22] block, cfq: get rid of queue preemption Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 07/22] block, cfq: get rid of workload type Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 08/22] block, cfq: get rid of latency tunables Paolo Valente
2016-02-10 23:05 ` Tejun Heo
2016-02-01 22:12 ` [PATCH RFC 09/22] block, cfq: replace CFQ with the BFQ-v0 I/O scheduler Paolo Valente
2016-02-11 22:22 ` Tejun Heo
2016-02-12 0:35 ` Mark Brown
2016-02-17 15:57 ` Tejun Heo
2016-02-17 16:02 ` Mark Brown
2016-02-17 17:04 ` Tejun Heo
2016-02-17 18:13 ` Jonathan Corbet
2016-02-17 19:45 ` Tejun Heo
2016-02-17 19:56 ` Jonathan Corbet
2016-02-17 20:14 ` Tejun Heo
2016-02-17 9:02 ` Paolo Valente
2016-02-17 17:02 ` Tejun Heo
2016-02-20 10:23 ` Paolo Valente
2016-02-20 11:02 ` Paolo Valente
2016-03-01 18:46 ` Tejun Heo
2016-03-04 17:29 ` Linus Walleij
2016-03-04 17:39 ` Christoph Hellwig
2016-03-04 18:10 ` Austin S. Hemmelgarn
2016-03-11 11:16 ` Christoph Hellwig
2016-03-11 13:38 ` Austin S. Hemmelgarn
2016-03-05 12:18 ` Linus Walleij
2016-03-11 11:17 ` Christoph Hellwig
2016-03-11 11:24 ` Nikolay Borisov
2016-03-11 11:49 ` Christoph Hellwig
2016-03-11 14:53 ` Linus Walleij
2016-03-09 6:55 ` Paolo Valente
2016-04-13 19:54 ` Tejun Heo
2016-04-14 5:03 ` Mark Brown
2016-03-09 6:34 ` Paolo Valente
2016-04-13 20:41 ` Tejun Heo
2016-04-14 10:23 ` Paolo Valente
2016-04-14 16:29 ` Tejun Heo
2016-04-15 14:20 ` Paolo Valente
2016-04-15 15:08 ` Tejun Heo
2016-04-15 16:17 ` Paolo Valente
2016-04-15 19:29 ` Tejun Heo
2016-04-15 22:08 ` Paolo Valente
2016-04-15 22:45 ` Tejun Heo
2016-04-16 6:03 ` Paolo Valente
2016-04-15 14:49 ` Linus Walleij
2016-02-01 22:12 ` [PATCH RFC 10/22] block, bfq: add full hierarchical scheduling and cgroups support Paolo Valente
2016-02-11 22:28 ` Tejun Heo
2016-02-17 9:07 ` Paolo Valente
2016-02-17 17:14 ` Tejun Heo
2016-02-17 17:45 ` Tejun Heo
2016-04-20 9:32 ` Paolo
2016-04-22 18:13 ` Tejun Heo
2016-04-22 18:19 ` Paolo Valente
2016-04-22 18:41 ` Tejun Heo
2016-04-22 19:05 ` Paolo Valente
2016-04-22 19:32 ` Tejun Heo
2016-04-23 7:07 ` Paolo Valente
2016-04-25 19:24 ` Tejun Heo
2016-04-25 20:30 ` Paolo
2016-05-06 20:20 ` Paolo Valente
2016-05-12 13:11 ` Paolo [this message]
2016-07-27 16:13 ` [PATCH RFC V8 00/22] Replace the CFQ I/O Scheduler with BFQ Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 01/22] block, cfq: remove queue merging for close cooperators Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 02/22] block, cfq: remove close-based preemption Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 03/22] block, cfq: remove deep seek queues logic Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 04/22] block, cfq: remove SSD-related logic Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 05/22] block, cfq: get rid of hierarchical support Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 06/22] block, cfq: get rid of queue preemption Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 07/22] block, cfq: get rid of workload type Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 08/22] block, cfq: get rid of latency tunables Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 09/22] block, cfq: replace CFQ with the BFQ-v0 I/O scheduler Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 10/22] block, bfq: add full hierarchical scheduling and cgroups support Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 11/22] block, bfq: improve throughput boosting Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 12/22] block, bfq: modify the peak-rate estimator Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 13/22] block, bfq: add more fairness with writes and slow processes Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 14/22] block, bfq: improve responsiveness Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 15/22] block, bfq: reduce I/O latency for soft real-time applications Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 16/22] block, bfq: preserve a low latency also with NCQ-capable drives Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 17/22] block, bfq: reduce latency during request-pool saturation Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 18/22] block, bfq: add Early Queue Merge (EQM) Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 19/22] block, bfq: reduce idling only in symmetric scenarios Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 20/22] block, bfq: boost the throughput on NCQ-capable flash-based devices Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 21/22] block, bfq: boost the throughput with random I/O on NCQ-capable HDDs Paolo Valente
2016-07-27 16:13 ` [PATCH RFC V8 22/22] block, bfq: handle bursts of queue activations Paolo Valente
2016-07-28 16:50 ` [PATCH RFC V8 00/22] Replace the CFQ I/O Scheduler with BFQ Paolo
2016-02-01 22:12 ` [PATCH RFC 11/22] block, bfq: improve throughput boosting Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 12/22] block, bfq: modify the peak-rate estimator Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 13/22] block, bfq: add more fairness to boost throughput and reduce latency Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 14/22] block, bfq: improve responsiveness Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 15/22] block, bfq: reduce I/O latency for soft real-time applications Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 16/22] block, bfq: preserve a low latency also with NCQ-capable drives Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 17/22] block, bfq: reduce latency during request-pool saturation Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 18/22] block, bfq: add Early Queue Merge (EQM) Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 19/22] block, bfq: reduce idling only in symmetric scenarios Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 20/22] block, bfq: boost the throughput on NCQ-capable flash-based devices Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 21/22] block, bfq: boost the throughput with random I/O on NCQ-capable HDDs Paolo Valente
2016-02-01 22:12 ` [PATCH RFC 22/22] block, bfq: handle bursts of queue activations Paolo Valente
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