linux-ext4 - Re: t_ext_jnl_rm test takes 96 seconds to finish

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Date:   Wed, 2 Oct 2019 15:59:48 -0500
From:   "A. Wilcox" <awilfox@...lielinux.org>
To:     "Theodore Y. Ts'o" <tytso@....edu>
Cc:     linux-ext4@...r.kernel.org
Subject: Re: t_ext_jnl_rm test takes 96 seconds to finish

On 02/10/2019 14:59, Theodore Y. Ts'o wrote:
> On Wed, Oct 02, 2019 at 01:16:51PM -0500, A. Wilcox wrote:
>> While building e2fsprogs 1.45.4, I noticed the following output during
>> testing:
>>
>> t_ext_jnl_rm: remove missing external journal device: ok
>> t_ext_jnl_rm:  *** took 96 seconds to finish ***
>> t_ext_jnl_rm:  consider adding t_ext_jnl_rm/is_slow_test
>>
>> I didn't see any mention of this in the list archives, and I'm not
>> entirely sure if it should really be marked as a slow test.
> 
> The first time I ran this test, it took 20 seconds.  (And that was
> only because I had a WDC external SSD attached to my laptop and it
> took time to spin it up; more on that below.)  The next time, it was
> nearly instaneous:
> 
> % time ./test_script t_ext_jnl_rm
> t_ext_jnl_rm: remove missing external journal device: ok
> 356 tests succeeded  0 tests failed
> 
> real	  0m0.242s
> user	  0m0.053s
> sys	  0m0.114s
> 
> If you look at the test script, you'll see that we are creating a file
> system, setting up an external journal which doesn't exist:
> 
> 
> ... and then we ask tune2fs to remove the journal:
> 
> 
> So the time that it takes is based on how long it takes to search all
> of the disks attached to the system looking for an external journal
> with the uuid 1db3f677-6832-4adb-bafc-8e4059c30a33.
> 
> On most systems, this is fast.  If you happen to have a slow device
> attached to your system, then this can take a while --- but there's
> really not much we can do about this.  I suppose we could try to add a
> test mock which disables the external journal search, if there isn't
> any way you can speed things up on your end now that you know what's
> causing the delay?
> 
> 						- Ted


Ah, okay.  This machine happened to have backup devices still connected
which are external USB spinning rust drives.  They could easily take 30+
seconds to spin up, each, and there were two.  Additionally it has a
caching HDD internally that may have been spun down.  That explains it.

Thank you for making sense of this, and doing so promptly.  I really
appreciate it!

Best,
--arw


-- 
A. Wilcox (awilfox)
Project Lead, Adélie Linux
https://www.adelielinux.org



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