linux-kernel - Re: [PATCH 4/4] drm/ttm: Optimize reservation slightly

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Message-ID: <5097C896.80805@vmware.com>
Date:	Mon, 05 Nov 2012 15:09:26 +0100
From:	Thomas Hellstrom <thellstrom@...are.com>
To:	Maarten Lankhorst <maarten.lankhorst@...onical.com>
CC:	airlied@...il.com, airlied@...hat.com,
	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 4/4] drm/ttm: Optimize reservation slightly

On 11/05/2012 03:01 PM, Maarten Lankhorst wrote:
> Hey,
>
> Op 05-11-12 14:31, Thomas Hellstrom schreef:
>> Reservation locking currently always takes place under the LRU spinlock.
>> Hence, strictly there is no need for an atomic_cmpxchg call; we can use
>> atomic_read followed by atomic_write since nobody else will ever reserve
>> without the lru spinlock held.
>> At least on Intel this should remove a locked bus cycle on successful
>> reserve.
>>
>> Signed-off-by: Thomas Hellstrom <thellstrom@...are.com>
>>
> Is that really a good thing to submit when I am busy killing lru lock around reserve? :-)
>

If your patch series makes it into the same kernel, let's kill this 
patch. Otherwise it may live
at least for a kernel release. It's not a big thing to rebase against, 
and I won't complain if your
patch adds another atomic read-modify-write op here. :)

/Thomas

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