Re: Progress indicator when (slowly) mounting a btrfs filesystem?

2016-02-01 Thread Christian Rohmann
Hey Chris,

On 01/28/2016 12:47 AM, Chris Murphy wrote:
> Might be a bug, but more likely might be a lack of optimization. If it
> eventually mounts without errors that's a pretty good plus. Lots of
> file systems can't handle power failures well at all.

So what and how should I go about profiling such a long running mount in
order to help finding point where optimization is needed the most then?

Just as a side note: I don't think it's your own expectation to be like
all those other file systems ;-)


Regards

Christian
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Re: Progress indicator when (slowly) mounting a btrfs filesystem?

2016-02-01 Thread Austin S. Hemmelgarn

On 2016-02-01 09:03, Christian Rohmann wrote:

Hey Chris,

On 01/28/2016 12:47 AM, Chris Murphy wrote:

Might be a bug, but more likely might be a lack of optimization. If it
eventually mounts without errors that's a pretty good plus. Lots of
file systems can't handle power failures well at all.


So what and how should I go about profiling such a long running mount in
order to help finding point where optimization is needed the most then?
It would probably require some work with perf and ftrace, which means 
you likely need to build a special kernel just for testing, and then 
generate an ideally clean-room like environment (whatever hosting, plus 
userspace, plus a consistent filesystem image that you can reuse for 
each test, etc).


Kernel profiling is a decidedly non-trivial task, and is not something I 
would recommend somebody try unless both:
a) They already have a working knowledge of kernel internals, or are 
willing to learn.

b) They have the time and resources to do it right in a reproducible manner.
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