linux-kernel - Re: [lustre-devel] staging: lustre: One function call less in class_register

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Date:	Fri, 29 Jul 2016 11:28:46 -0400
From:	Oleg Drokin <oleg.drokin@...el.com>
To:	SF Markus Elfring <elfring@...rs.sourceforge.net>
Cc:	<devel@...verdev.osuosl.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	<kernel-janitors@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Julia Lawall <julia.lawall@...6.fr>,
	"Bhumika Goyal" <bhumirks@...il.com>,
	<lustre-devel@...ts.lustre.org>
Subject: Re: [lustre-devel] staging: lustre: One function call less in class_register_type() after error detection


On Jul 28, 2016, at 1:53 AM, SF Markus Elfring wrote:

>> This function is called several times during lustre module insert.
>> Namely it's called 5 times for 5 types:
>> osc, mdc, lov, lmv, mgc.
> 
> Will any extra memory accesses matter for the successful execution
> in this use case?

I doubt it.

In typical deployments outside of testing environment, this function is
called 5 times every system boot and never again.

>> It's not called any more than that, so it's not exactly a super hot-path function
>> to overoptimize it, and the failure is presumed to never happen too
>> (or the module would be non-functional).
> 
> Did the assignment for the local variable "rc" with a well-known error code
> influence the run-time characteristics in unwanted ways?
> https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/tree/drivers/staging/lustre/lustre/obdclass/genops.c?id=6a5b99a46bedc2cfbba96dec6d255c4b90af9ff8#n140

I am not sure what do you mean here.