linux-kernel - Re: missing madvise functionality

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Message-ID: <20070403200936.GA25541@one.firstfloor.org>
Date:	Tue, 3 Apr 2007 22:09:36 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Ulrich Drepper <drepper@...hat.com>,
	Rik van Riel <riel@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Jakub Jelinek <jakub@...hat.com>, linux-mm@...ck.org,
	Hugh Dickins <hugh@...itas.com>
Subject: Re: missing madvise functionality

> It might, a bit.  Both mmap() and mprotect() currently take mmap_sem() for
> writing.  If we're careful, we could probably arrange for MADV_ULRICH to
> take it for reading, which will help a little bit, hopefully.

The cache line bounces would be still there. Not sure that would help MySQL
all that much. 

Besides if the down_write is the real problem one could convert 
the code for all cases over to optimistic locking assuming most calls 
don't merge.

-Andi
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