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Date: Tue, 6 Feb 2024 17:43:13 +0200
From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Howard Yen <howardyen@google.com>
Cc: hch@lst.de, m.szyprowski@samsung.com, robin.murphy@arm.com,
	gregkh@linuxfoundation.org, rafael@kernel.org, broonie@kernel.org,
	james@equiv.tech, james.clark@arm.com, masahiroy@kernel.org,
	linux-kernel@vger.kernel.org, iommu@lists.linux.dev
Subject: Re: [PATCH v2] dma-coherent: add support for multi coherent rmems
 per dev
Message-ID: <ZcJTkQFcVhcGC52Z@smile.fi.intel.com>
References: <20240205072312.2342188-1-howardyen@google.com>
 <ZcDPn5eLvMwpb7N1@smile.fi.intel.com>
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Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo

On Mon, Feb 05, 2024 at 02:08:00PM +0200, Andy Shevchenko wrote:
> On Mon, Feb 05, 2024 at 07:23:00AM +0000, Howard Yen wrote:

..

> > @@ -18,15 +18,9 @@ struct dma_coherent_mem {
> >  	unsigned long	*bitmap;
> >  	spinlock_t	spinlock;
> >  	bool		use_dev_dma_pfn_offset;
> > +	struct list_head	node;
> 
> Have you run `pahole`? Here I see wasted bytes for nothing.

On top of that one may make container_of() to be no-op, by placing this member
to be the first one. But, double check this with bloat-o-meter (that it indeed
does better code generation) and on the other hand check if the current first
member is not performance critical and having additional pointer arithmetics is
okay.

> >  };


-- 
With Best Regards,
Andy Shevchenko