Re: mount btrfs takes 30 minutes, btrfs check runs out of memory

[Qu Wenruo <quwenruo@cn.fujitsu.com>]

John Ettedgui wrote on 2015/07/29 18:55 +0000:
> Hello,
> I have the same issue and would like to add myself to this thread.
> My btrfs partition is about 10tb on top of lvm2 and has been taking about a minute to mount in the past few months.
>
>> Qu Wenruo <quwenruo <at>cn.fujitsu.com <http://cn.fujitsu.com>> writes:
>>
>> Quite common, especial when it grows large.
>> But it would be much better to use ftrace to show which btrfs operation
>> takes the most time.
>
>
> I have got a trace file running this command:
> trace-cmd record -e btrfs mount <PARTITION>
>
> Since it is fairly big for an email I have gzipped it.
>
> Thanks!
> John
>
Hi John,
Thanks for the trace output.

But it seems that, your root partition is also btrfs, causing a lot of 
btrfs trace from your systemd journal.

Would you mind re-collecting the ftrace without such logging system 
caused btrfs trace?

BTW, although I'm not quite familiar with ftrace, would you please 
consider collect ftrace with function_graph tracer?
That would help a lot to find which takes the most time.
But it may trace too much things and maybe hard to read.

Thanks,
Qu