linux-kernel - Re: [PATCH] liquidio: lio_main: remove unnecessary static in setup_io

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Message-ID: <20170718210551.GB1176@felix-thinkpad.cavium.com>
Date:   Tue, 18 Jul 2017 14:05:51 -0700
From:   Felix Manlunas <felix.manlunas@...ium.com>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     Derek Chickles <derek.chickles@...iumnetworks.com>,
        Satanand Burla <satananda.burla@...iumnetworks.com>,
        Felix Manlunas <felix.manlunas@...iumnetworks.com>,
        Raghu Vatsavayi <raghu.vatsavayi@...iumnetworks.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] liquidio: lio_main: remove unnecessary static in
 setup_io_queues()

On Tue, Jul 18, 2017 at 03:53:48PM -0500, Gustavo A. R. Silva wrote:
> Remove unnecessary static on local variables cpu_id_modulus and cpu_id.
> Such variables are initialized before being used, on every execution
> path throughout the function. The static has no benefit and, removing
> it reduces the object file size.
> 
> This issue was detected using Coccinelle and the following semantic patch:
> 
> @bad exists@
> position p;
> identifier x;
> type T;
> @@
> 
> static T x@p;
> ...
> x = <+...x...+>
> 
> @@
> identifier x;
> expression e;
> type T;
> position p != bad.p;
> @@
> 
> -static
>  T x@p;
>  ... when != x
>      when strict
> ?x = e;
> 
> In the following log you can see a significant difference in the object
> file size. Also, there is a significant difference in the bss segment.
> This log is the output of the size command, before and after the code
> change:
> 
> before:
>    text    data     bss     dec     hex filename
>   78689   15272   27808  121769   1dba9 drivers/net/ethernet/cavium/liquidio/lio_main.o
> 
> after:
>    text    data     bss     dec     hex filename
>   78667   15128   27680  121475   1da83 drivers/net/ethernet/cavium/liquidio/lio_main.o
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
> ---
>  drivers/net/ethernet/cavium/liquidio/lio_main.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/cavium/liquidio/lio_main.c b/drivers/net/ethernet/cavium/liquidio/lio_main.c
> index 51583ae..1d8fefa 100644
> --- a/drivers/net/ethernet/cavium/liquidio/lio_main.c
> +++ b/drivers/net/ethernet/cavium/liquidio/lio_main.c
> @@ -2544,8 +2544,8 @@ static inline int setup_io_queues(struct octeon_device *octeon_dev,
>  {
>  	struct octeon_droq_ops droq_ops;
>  	struct net_device *netdev;
> -	static int cpu_id;
> -	static int cpu_id_modulus;
> +	int cpu_id;
> +	int cpu_id_modulus;
>  	struct octeon_droq *droq;
>  	struct napi_struct *napi;
>  	int q, q_no, retval = 0;
> -- 
> 2.5.0
> 

Thanks.

Acked-by: Felix Manlunas <felix.manlunas@...ium.com>