linux-kernel - Re: [PATCH] radeon: Deinline indirect register accessor functions

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Message-ID: <555A3461.90000@redhat.com>
Date:	Mon, 18 May 2015 20:50:09 +0200
From:	Denys Vlasenko <dvlasenk@...hat.com>
To:	Christian König <christian.koenig@....com>
CC:	Alex Deucher <alexander.deucher@....com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] radeon: Deinline indirect register accessor functions

On 05/18/2015 08:06 PM, Christian König wrote:
> I'm actually surprised how often people come along with that. The last time we tried this it caused a noticeable performance drop.
> 
> Basic problem is that this line:
>> +    if ((reg < rdev->rmmio_size || reg < RADEON_MIN_MMIO_SIZE) && !always_indirect)
> optimizes away in most of the cases which reduces the call to a readl which is way faster than the spinlock path.
> 
> So this is a NAK,


Fair enough.

I'm preparing a v2 where the fast branch of r100_mm_{r,w}reg() will stay inlined.

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