linux-kernel - RE: [PATCH 3/3 v3] net/macb: Try to optimize struct macb layout

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Message-ID: <AE90C24D6B3A694183C094C60CF0A2F6026B723B@saturn3.aculab.com>
Date:	Wed, 15 May 2013 10:38:44 +0100
From:	"David Laight" <David.Laight@...LAB.COM>
To:	"Nicolas Ferre" <nicolas.ferre@...el.com>,
	"David S. Miller" <davem@...emloft.net>, <netdev@...r.kernel.org>
Cc:	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>,
	"Jean-Christophe PLAGNIOL-VILLARD" <plagnioj@...osoft.com>,
	<hein_tibosch@...oo.es>, <s.trumtrar@...gutronix.de>,
	<michal.simek@...inx.com>, <monstr@...str.eu>,
	"Havard Skinnemoen" <havard@...nnemoen.net>
Subject: RE: [PATCH 3/3 v3] net/macb: Try to optimize struct macb layout

> Move TX-related fields to the top of the struct so that they end up on
> the same cache line. Move the NAPI struct below that since it is used
> from the interrupt handler. This field is also marked as
> ___cacheline_aligned_in_smp.
> RX-related fields go below those.
> Function pointers and capability mask are immediately after that as
> they are also used in the hot path.
> 
> Move the spinlock before regs since they are usually used together.

Haven't you introduced some holes in the structure?
I suspect that spinloack_t might only be 32bits on
some 64bit systems.
There is certainly one where 'caps' used to be.

...> 
>  struct macb {
> +	spinlock_t		lock;
>  	void __iomem		*regs;
...
> +	struct macb_or_gem_ops	macbgem_ops;
> +
> +	u32			caps;
> 
> -	spinlock_t		lock;
>  	struct platform_device	*pdev;

	David



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