From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Date: Mon, 16 Aug 2004 00:12:38 +0000 Subject: Re: page fault fastpath: Increasing SMP scalability by introducing pte locks? Message-Id: <20040816001238.GA6978@muc.de> List-Id: References: <2ttIr-2e4-17@gated-at.bofh.it> <2tzE4-6sw-25@gated-at.bofh.it> <2tCiw-8pK-1@gated-at.bofh.it> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Christoph Lameter Cc: Christoph Lameter , linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org On Sun, Aug 15, 2004 at 04:55:57PM -0700, Christoph Lameter wrote: > On Mon, 16 Aug 2004, Andi Kleen wrote: > > > Christoph Lameter writes: > > > > > On Sun, 15 Aug 2004, David S. Miller wrote: > > > > > >> > > >> Is the read lock in the VMA semaphore enough to let you do > > >> the pgd/pmd walking without the page_table_lock? > > >> I think it is, but just checking. > > > > > > That would be great.... May I change the page_table lock to > > > be a read write spinlock instead? > > > > That's probably not a good idea. r/w locks are extremly slow on > > some architectures. Including ia64. > > I was thinking about a read write spinlock not an readwrite > semaphore. Look at include/asm-ia64/spinlock.h. I was also talking about rw spinlocks. > The implementations are almost the same. Are you sure > about this? Yes. Try the cat /proc/net/tcp test. It will take >100k read locks for the TCP listen hash table, and on bigger ppc64 and ia64 machines this can take nearly a second of system time. -Andi