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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
Subject: Re: [PATCH RFC 10/22] block, bfq: add full hierarchical scheduling and cgroups support
Date: Wed, 20 Apr 2016 11:32:23 +0200	[thread overview]
Message-ID: <57174CA7.5000706@linaro.org> (raw)
In-Reply-To: <20160211222824.GD3741@mtj.duckdns.org>

[Resending in plain text]

Il 11/02/2016 23:28, Tejun Heo ha scritto:
> Hello,  > > On Mon, Feb 01, 2016 at 11:12:46PM +0100, Paolo Valente wrote: >> 
From: Arianna Avanzini <avanzini.arianna@gmail.com> >> >> Complete 
support for full hierarchical scheduling, with a cgroups >> interface. 
The name of the added policy is bfq. >> >> Weights can be assigned 
explicitly to groups and processes through the >> cgroups interface, 
differently from what happens, for single >> processes, if the cgroups 
interface is not used (as explained in the >> description of the 
previous patch). In particular, since each node has >> a full scheduler, 
each group can be assigned its own weight. > > * It'd be great if how 
cgroup support is achieved is better >   documented. > > * How's 
writeback handled? > > * After all patches are applied, both 
CONFIG_BFQ_GROUP_IOSCHED and >   CONFIG_CFQ_GROUP_IOSCHED exist. > > * 
The default weight and weight range don't seem to follow the defined >   
interface on the v2 hierarchy.  The default value should be 100. > > * 
With all patches applied, booting triggers a RCU context warning. >   
Please build with lockdep and RCU debugging turned on and fix the >   
issue. > > * I was testing on the v2 hierarchy with two top-level 
cgroups one >   hosting sequential workload and the other completely 
random.  While >   they eventually converged to a reasonable state, 
starting up the >   sequential workload while the random workload was 
running was >   extremely slow.  It crawled for quite a while.

This malfunction seems related to a blkcg behavior that I did not
expect: the sequential writer changes group continuously. It moves
from the root group to its correct group, and back. Here is the
output of

egrep 'insert_request|changed cgroup' trace

over a trace taken with the original version of cfq (seq_write is of
course the group of the writer):

     kworker/u8:2-96    [000] d...   204.561086:   8,0    m   N cfq96A  
/seq_write changed cgroup
     kworker/u8:2-96    [000] d...   204.561097:   8,0    m   N cfq96A  
/ changed cgroup
     kworker/u8:2-96    [000] d...   204.561353:   8,0    m   N cfq96A  
/ insert_request
     kworker/u8:2-96    [000] d...   204.561369:   8,0    m   N cfq96A  
/seq_write insert_request
     kworker/u8:2-96    [000] d...   204.561379:   8,0    m   N cfq96A  
/seq_write insert_request
     kworker/u8:2-96    [000] d...   204.566509:   8,0    m   N cfq96A  
/seq_write changed cgroup
     kworker/u8:2-96    [000] d...   204.566517:   8,0    m   N cfq96A  
/ changed cgroup
     kworker/u8:2-96    [000] d...   204.566690:   8,0    m   N cfq96A  
/ insert_request
     kworker/u8:2-96    [000] d...   204.567203:   8,0    m   N cfq96A  
/seq_write insert_request
     kworker/u8:2-96    [000] d...   204.567216:   8,0    m   N cfq96A  
/seq_write insert_request
     kworker/u8:2-96    [000] d...   204.567328:   8,0    m   N cfq96A  
/seq_write insert_request
     kworker/u8:2-96    [000] d...   204.571622:   8,0    m   N cfq96A  
/seq_write changed cgroup
     kworker/u8:2-96    [000] d...   204.571640:   8,0    m   N cfq96A  
/ changed cgroup
     kworker/u8:2-96    [000] d...   204.572021:   8,0    m   N cfq96A  
/ insert_request
     kworker/u8:2-96    [000] d...   204.572463:   8,0    m   N cfq96A  
/seq_write insert_request
...

For reasons that I don't yet know, group changes are much more
frequent with bfq, which ultimately causes bfq to fail to isolate the
writer from the reader.

While I go on trying to understand why, could you please tell me
whether this fluctuation is normal, and/or point me to documentation from
which I can better understand this behavior, without bothering you
further?

Thanks,
Paolo

>  > * And "echo 100 > io.weight" hung the writing process. > > Thanks. >

  parent reply	other threads:[~2016-04-20  9:32 UTC|newest]

Thread overview: 109+ 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  9:07       ` Paolo Valente
2016-02-17 17:14       ` Tejun Heo
2016-02-17 17:45         ` Tejun Heo
2016-04-20  9:21     ` Paolo
2016-04-20  9:32     ` Paolo [this message]
2016-04-22 18:13       ` Tejun Heo
2016-04-22 18:19         ` Paolo Valente
2016-04-22 18:19           ` Paolo Valente
2016-04-22 18:41           ` Tejun Heo
2016-04-22 19:05             ` Paolo Valente
2016-04-22 19:05               ` Paolo Valente
2016-04-22 19:32               ` Tejun Heo
2016-04-23  7:07                 ` Paolo Valente
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
2016-05-06 20:20                         ` Paolo Valente
2016-05-12 13:11                         ` Paolo
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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