Message-ID: <43C7C4C7.8050409@cfl.rr.com>
Date: Fri, 13 Jan 2006 10:18:31 -0500
From: Phillip Susi <psusi@cfl.rr.com>
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To: Dave McCracken <dmccr@us.ibm.com>
Cc: Hugh Dickins <hugh@veritas.com>, Andrew Morton <akpm@osdl.org>,
       Linux Kernel <linux-kernel@vger.kernel.org>,
       Linux Memory Management <linux-mm@kvack.org>
Subject: Re: [PATCH/RFC] Shared page tables
References: <A6D73CCDC544257F3D97F143@[10.1.1.4]>
In-Reply-To: <A6D73CCDC544257F3D97F143@[10.1.1.4]>
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Shouldn't those kind of applications already be using threads to share 
page tables rather than forking hundreds of processes that all mmap() 
the same file?


Dave McCracken wrote:
> Here's a new version of my shared page tables patch.
>
> The primary purpose of sharing page tables is improved performance for
> large applications that share big memory areas between multiple processes.
> It eliminates the redundant page tables and significantly reduces the
> number of minor page faults.  Tests show significant performance
> improvement for large database applications, including those using large
> pages.  There is no measurable performance degradation for small processes.
>
> This version of the patch uses Hugh's new locking mechanism, extending it
> up the page table tree as far as necessary for proper concurrency control.
>
> The patch also includes the proper locking for following the vma chains.
>
> Hugh, I believe I have all the lock points nailed down.  I'd appreciate
> your input on any I might have missed.
>
> The architectures supported are i386 and x86_64.  I'm working on 64 bit
> ppc, but there are still some issues around proper segment handling that
> need more testing.  This will be available in a separate patch once it's
> solid.
>
> Dave McCracken
>   

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