Re: IB/hfi1: Adjust another size determination in hfi1_user_sdma_alloc_queues()

From: SF Markus Elfring <elfring@users.sourceforge.net>
To: Johannes Thumshirn <jthumshirn@suse.de>, linux-rdma@vger.kernel.org
Cc: Dennis Dalessandro <dennis.dalessandro@intel.com>,
	Doug Ledford <dledford@redhat.com>,
	Hal Rosenstock <hal.rosenstock@gmail.com>,
	Mike Marciniszyn <mike.marciniszyn@intel.com>,
	Sean Hefty <sean.hefty@intel.com>,
	LKML <linux-kernel@vger.kernel.org>,
	kernel-janitors@vger.kernel.org
Subject: Re: IB/hfi1: Adjust another size determination in hfi1_user_sdma_alloc_queues()
Date: Mon, 13 Feb 2017 11:37:19 +0100	[thread overview]
Message-ID: <8ec653df-9d73-3c94-9559-7a732417e578@users.sourceforge.net> (raw)
In-Reply-To: <9ce8c7b1-1ae5-fe15-2740-b4f7653555c4@suse.de>

>> How often does it really make sense to keep such a product in this local variable?
> 
> It depends. Lets take it the other way round. If I this in a review I'd
> suggest the submitter to create a local variable for the multiplication
> to get rid of the line break. It's avoidable.

I imagine that there are further possibilities to improve the involved
programming for various arrays.

> And again, the compiler will optimize it away.
> 
> Apart from the fact that you haven't tested your patch at all:

This is true in principle as I could compile the source code adjustment at least.

> jthumshirn@linux-x5ow:linux (test)$ git am ~/\[PATCH\ 3_5\]\ IB_hfi1\:\
> Adjust\ another\ size\ determination\ in\
> hfi1_user_sdma_alloc_queues\(\).eml
> Applying: IB/hfi1: Adjust another size determination in
> hfi1_user_sdma_alloc_queues()
> jthumshirn@linux-x5ow:linux (test)$ make
> drivers/infiniband/hw/hfi1/user_sdma.o  CHK
> include/config/kernel.release
>   CHK     include/generated/uapi/linux/version.h
>   CHK     include/generated/utsrelease.h
>   CHK     include/generated/bounds.h
>   CHK     include/generated/timeconst.h
>   CHK     include/generated/asm-offsets.h
>   CALL    scripts/checksyscalls.sh
>   CC      drivers/infiniband/hw/hfi1/user_sdma.o
> drivers/infiniband/hw/hfi1/user_sdma.c: In function
> ‘hfi1_user_sdma_alloc_queues’:
> drivers/infiniband/hw/hfi1/user_sdma.c:402:2: error: ‘memsize’
> undeclared (first use in this function)
>   memsize = sizeof(*pq->reqs) * hfi1_sdma_comp_ring_size;
>   ^

How do you think about to apply also the previous update step like “[PATCH 2/5] IB/hfi1:
Use kcalloc() in hfi1_user_sdma_alloc_queues()”?

> So to sum up: there is no evident improvement in the resulting binary

There might not be a remarkable difference with the default software build parameters.

> and you introduce a stylistic glitch (the new line break in a function call).

There are different opinions about this implementation detail, aren't there?

Regards,
Markus