Date: Thu, 10 Nov 2005 13:21:25 +0000 (GMT)
From: Hugh Dickins <hugh@veritas.com>
To: "Michael S. Tsirkin" <mst@mellanox.co.il>
cc: Gleb Natapov <gleb@minantech.com>,
       Benjamin Herrenschmidt <benh@kernel.crashing.org>,
       Petr Vandrovec <vandrove@vc.cvut.cz>,
       Nick Piggin <nickpiggin@yahoo.com.au>,
       Badari Pulavarty <pbadari@us.ibm.com>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Nick's core remove PageReserved broke vmware...
In-Reply-To: <20051110131630.GF16589@mellanox.co.il>
Message-ID: <Pine.LNX.4.61.0511101316320.7422@goblin.wat.veritas.com>
References: <20051110124949.GM8942@minantech.com> <20051110131630.GF16589@mellanox.co.il>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 928
Lines: 25

On Thu, 10 Nov 2005, Michael S. Tsirkin wrote:
> Quoting Gleb Natapov <gleb@minantech.com>:
> > On Thu, Nov 10, 2005 at 02:48:53PM +0200, Michael S. Tsirkin wrote:
> > > > Also perhapse we should skip VM_SHARED VMAs?
> > > 
> > > Why?
> > > 
> > They will work correctly across fork(). 
> 
> So why would I call madvise on such a VMA?

To avoid the overhead of forking it e.g. if it's a large nonlinear vma,
a lot of time may be wasted on copying its ptes for fork.  That's one
of the reasons I came to like your DONTCOPY.

So, it may not be useful for your particular RDMA issue, but I see no
reason to exclude VM_SHARED vmas from the madvise, and good reason to
include them.

Hugh
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/