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From: Eric Sandeen <sandeen@sandeen.net>
To: Mike Snitzer <snitzer@redhat.com>, Ilya Dryomov <idryomov@gmail.com>
Cc: Dave Chinner <david@fromorbit.com>,
	xfs <linux-xfs@vger.kernel.org>, Mark Nelson <mnelson@redhat.com>,
	Eric Sandeen <sandeen@redhat.com>
Subject: Re: mkfs.xfs: don't go into multidisk mode if there is only one stripe
Date: Fri, 5 Oct 2018 09:55:57 -0500	[thread overview]
Message-ID: <5f6d3d86-7e56-dcf7-fb3d-3c3bc54ebc97@sandeen.net> (raw)
In-Reply-To: <20181005145001.GA4883@redhat.com>



On 10/5/18 9:50 AM, Mike Snitzer wrote:
> On Fri, Oct 05 2018 at  7:27am -0400,
> Ilya Dryomov <idryomov@gmail.com> wrote:
> 
>> On Fri, Oct 5, 2018 at 12:29 AM Dave Chinner <david@fromorbit.com> wrote:
>>>
>>> On Thu, Oct 04, 2018 at 01:33:12PM -0500, Eric Sandeen wrote:
>>>> On 10/4/18 12:58 PM, Ilya Dryomov wrote:
>>>>> rbd devices report the following geometry:
>>>>>
>>>>>   $ blockdev --getss --getpbsz --getiomin --getioopt /dev/rbd0
>>>>>   512
>>>>>   512
>>>>>   4194304
>>>>>   4194304
>>>
>>> dm-thinp does this as well. THis is from the thinp device created
>>> by tests/generic/459:
>>>
>>> 512
>>> 4096
>>> 65536
>>> 65536
>>
>> (adding Mike)
>>
>> ... and that 300M filesystem ends up with 8 AGs, when normally you get
>> 4 AGs for anything less than 4T.  Is that really intended?
>>
>> AFAIK dm-thinp reports these values for the same exact reason as rbd:
>> we are passing up the information about the efficient I/O size.  In the
>> case of dm-thinp, this is the thinp block size.  If you put dm-thinp on
>> top of a RAID array, I suspect it would pass up the array's preferred
>> sizes, as long as they are a proper factor of the thinp block size.
> 
> Right, see pool_io_hints() for all the logic thinp uses to consume block
> core's blk_stack_limits() provided limits.. thinp can override if the
> underlying limits are _not_ a factor of the thinp's blocksize.
> 
>> The high agcount on dm-thinp has come up before and you suggested that
>> dm-thinp should report iomin == ioopt (i.e. sunit == swidth).  If that
>> was the right fix back in 2014, mkfs.xfs must have regressed:
>>
>>   https://marc.info/?l=linux-xfs&m=137783388617206&w=2
>>   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=fdfb4c8c1a9fc8dd8cf8eeb4e3ed83573b375285
> 
> Yeah, if we're getting larger AG count again, certainly seems like
> mkfs.xfs regressed.

Our emails crossed ;) - no, there's no regression.  Dave's comment about
the thinp values weren't related to the mkfs AG heuristic.

-Eric

  reply	other threads:[~2018-10-05 21:55 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-04 17:58 [PATCH] mkfs.xfs: don't go into multidisk mode if there is only one stripe Ilya Dryomov
2018-10-04 18:33 ` Eric Sandeen
2018-10-04 18:56   ` Ilya Dryomov
2018-10-04 22:29   ` Dave Chinner
2018-10-05 11:27     ` Ilya Dryomov
2018-10-05 13:51       ` Eric Sandeen
2018-10-05 23:27         ` Dave Chinner
2018-10-06 12:17           ` Ilya Dryomov
2018-10-06 23:20             ` Dave Chinner
2018-10-07  0:14               ` Eric Sandeen
2018-11-29 13:53                 ` Ric Wheeler
2018-11-29 21:48                   ` Dave Chinner
2018-11-29 23:53                     ` Ric Wheeler
2018-11-30  2:25                       ` Dave Chinner
2018-11-30 18:00                         ` block layer API for file system creation - when to use multidisk mode Ric Wheeler
2018-11-30 18:00                           ` Ric Wheeler
2018-11-30 18:05                           ` Mark Nelson
2018-11-30 18:05                             ` Mark Nelson
2018-12-01  4:35                           ` Dave Chinner
2018-12-01  4:35                             ` Dave Chinner
2018-12-01 20:52                             ` Ric Wheeler
2018-12-01 20:52                               ` Ric Wheeler
2018-10-07 13:54               ` [PATCH] mkfs.xfs: don't go into multidisk mode if there is only one stripe Ilya Dryomov
2018-10-10  0:28                 ` Dave Chinner
2018-10-05 14:50       ` Mike Snitzer
2018-10-05 14:55         ` Eric Sandeen [this message]
2018-10-05 17:21           ` Ilya Dryomov

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