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Date:      Tue, 26 May 2015 09:16:23 -0700
From:      Alexander Motin <mav@FreeBSD.org>
To:        Neel Natu <neelnatu@gmail.com>,  Garrett Cooper <yaneurabeya@gmail.com>
Cc:        FreeBSD Current <freebsd-current@freebsd.org>,  "freebsd-testing@freebsd.org" <freebsd-testing@freebsd.org>, Peter Grehan <grehan@freebsd.org>
Subject:   Re: cam(4) timeouts in bhyve/kyua runs up on Jenkins?
Message-ID:  <55649C57.1080906@FreeBSD.org>
In-Reply-To: <CAFgRE9HR5AOeTqOfFD4Wzg3Zbp%2BF4n1_MOBzd8k%2B1qJjVhp_AA@mail.gmail.com>
References:  <28845361-E624-4CB9-B255-1B2C1FD0DF28@gmail.com>	<4BEE0A54-3AD2-42DB-AF4E-2B0A5E34DF4E@gmail.com>	<553F3CA7.9090601@FreeBSD.org>	<9FBE053A-971A-433E-9B88-D62CF9273CFB@gmail.com> <CAFgRE9HR5AOeTqOfFD4Wzg3Zbp%2BF4n1_MOBzd8k%2B1qJjVhp_AA@mail.gmail.com>

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On 26.05.2015 09:06, Neel Natu wrote:
> On Mon, May 25, 2015 at 1:40 PM, Garrett Cooper <yaneurabeya@gmail.com> wrote:
>> On Apr 28, 2015, at 0:54, Alexander Motin <mav@FreeBSD.org> wrote:
>>> On 27.04.2015 21:17, Garrett Cooper wrote:
>>>> On Apr 27, 2015, at 11:16, Garrett Cooper <yaneurabeya@gmail.com>
>>>> wrote:
>>>>
>>>>> I was looking at the console log for the latest kyua run and I’ve
>>>>> noticed that it’s timing out a bit more [1] than it was
>>>>> previously [2]. I’ve seen some of your commits recently to cam(4)
>>>>> dealing with bhyve — has there been a performance regression
>>>>> there? Thanks! -NGie
>>>>>
>>>>> 1.
>>>>> https://jenkins.freebsd.org/job/FreeBSD_HEAD-tests2/940/console
>>>>> 2.
>>>>> https://jenkins.freebsd.org/job/FreeBSD_HEAD-tests2/983/console
>>>>
>>>> (Sorry for not being more explicit for the archives) These are the
>>>> timeouts I’m referring to:
>>>>
>>>> ahcich0: is 00000000 cs 00000000 ss 1f000000 rs 1f000000 tfd 50
>>>> serr 00000000 cmd 1000dc17 (ada0:ahcich0:0:0:0):
>>>> WRITE_FPDMA_QUEUED. ACB: 61 08 a8 54 1e 40 00 00 00 00 00 00
>>>> (ada0:ahcich0:0:0:0): CAM status: Command timeout
>>>> (ada0:ahcich0:0:0:0): Retrying command
> 
> Can you try to reproduce with a virtio-blk instead of ahci-hd?
> 
> It will help narrow down the problem because both ahci-hd and
> virtio-blk emulations share a common backend to read/write to the
> disk.

virtio-blk has no command timeouts, so it may be problematic to notice
delayed commands there, unless they stuck forever. This won't be fair
comparison. Though if not use TRIM, virtio-blk should be more efficient
now, as it is supposed to.

>>> Last time I was more working on bhyve host disk emulation, rather then
>>> on cam(4) running on guest. Considering that, what guest and what host
>>> versions are you running? Is there any other load on host except this VM
>>> that could cause I/O delays high enough to trigger timeouts? What are
>>> you using to back the virtual disk (file, zvol, ...)?
>>
>> I have no idea what the Jenkins slaves are running in terms of configuration/version/etc. You’ll have to ask jenkins-admin@…
>> Thanks!
>> -NGie


-- 
Alexander Motin



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