From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Charbonnet Subject: Re: x86-64 Net Performance Date: Sun, 9 Oct 2005 14:47:18 -0500 Message-ID: <200510091447.19062.alexander@charbonnet.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Disposition: inline List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Ian Pratt Cc: xen-devel@lists.xensource.com, Nicholas Lee List-Id: xen-devel@lists.xenproject.org I did `apt-get source glibc`, edited debian/sysdeps/amd64.mk to comment out the couple of lines enabling NPTL, then used dpkg-buildpackage to generate new .debs. Your skepticism was warranted; I double-checked my changes to that file, and I had also disabled a line that set -O3 for the compile. This seems to account for the performance difference on native; recompiling with -O3 intact slows things down to normal. So the conclusion is that NPTL / TLS doesn't make much difference. However, it's kind of odd that disabling -O3 would make things faster on native, but have no effect on Xen. Alex On Sunday 09 October 2005 04:18 am, Ian Pratt wrote: > > Update: I went ahead and compiled glibc without TLS / NPTL. > > For 64 bit Xen you don't need to worry about TLS/NPTL. > > > Also, I realized that I wasn't allocating all my physical > > memory to Domain0 for these tests, so I was giving Xen a > > disadvantage. It didn't change much, but those tests have > > been re-done. > > > > Here's the odd thing: disabling TLS for 64-bit improved > > native performance by around 10%, but had no effect on Xen. > > How did you disable TLS on 64 bit? It's odd that it would have any > effect on native or xen, let alone such a dramatic one. Are you sure > about this test? > > > Native Domain0 Penalty > > 64-bit TLS 50.2 65.0 29.5% > > 64-bit no TLS 44.8 65.0 45.1% > > 32-bit TLS 59.6 59.5 -0.2% > > 32-bit no TLS 59.6 60.2 1.0% > > It looks like we need to investigate x86_64 networking performance. We > may well not be getting the pipelining that we do in 32bit, though I > can't immediately think why, > > Ian