Re: MD-RAID: Use seq_putc() in three status functions?

From: SF Markus Elfring
Date: Mon Oct 17 2016 - 07:17:37 EST

>> * Is a string pointer often longer than a byte?
> Always.

I have got doubts for this specific information.

> (Which up to now I thought was basic programming knowledge...)

By the way:
Run time environments still exist where the size of a pointer can be also
just one byte, don't they?

>> How many results would we like to clarify from various hardware
>> and software combinations?
> See above. At the moment _any_ test result from your side would do.

I imagine that another single result might not be representative.
How many lessons from test statistics will usually be also relevant here?

>> How important are the mentioned functions for you within the Linux
>> programming interface so far?
> Not very. The interface is only used in a slow path, and the execution
> time doesn't affect I/O performance in any way.

Thanks for another interesting information.

>>> Case in point: with your patch the x86_64 compiler generates nearly
>>> identical code for driver/md/raid1.c, but with one instruction _more_
>>> after your patch has been applied.
>> Which software versions and command parameters did you try out
>> for this information (from an unspecified run time environment)?
> # gcc --version
> gcc (SUSE Linux) 4.8.5

Thanks for this detail.

* Did you choose any special optimisation settings for your quick check?

* Will any compilation results matter if "optimisation" would be
switched off there?

> I'm still waiting from results from your side.

Would any other software developers or testers dare to add related information?