Messages in this thread | | | From | Paul Durrant <> | Subject | RE: [PATCH net-next v7 9/9] xen-netback: Aggregate TX unmap operations | Date | Thu, 20 Mar 2014 11:14:51 +0000 |
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> -----Original Message----- > From: Wei Liu [mailto:wei.liu2@citrix.com] > Sent: 20 March 2014 10:49 > To: Zoltan Kiss > Cc: Ian Campbell; Wei Liu; xen-devel@lists.xenproject.org; > netdev@vger.kernel.org; linux-kernel@vger.kernel.org; Jonathan Davies; > Paul Durrant > Subject: Re: [PATCH net-next v7 9/9] xen-netback: Aggregate TX unmap > operations > > On Wed, Mar 19, 2014 at 09:16:05PM +0000, Zoltan Kiss wrote: > > Hi, > > > > I'm thinking about revoking this patch: it's value is pretty small, > > but it causes performance regression on Win7 guests. And probably it > > is not the best solution for this problem. It might be the delay it > > takes the dealloc thread to be scheduled is enough. > > What do you think? > > > > Can you elaborate? What makes Win7 so special? What's performance > impact to other guests? >
It won't be Win7 specifically I expect. It will likely by any version of Windows, or any other OS that limits the TXs-in-flight so aggressively. Basically you need to TX-complete reasonably frequently otherwise your throughput drops off a lot. IIRC at Solarflare we found every ~500us to be just about frequent enough for hitting 10G.
Paul
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