From mboxrd@z Thu Jan 1 00:00:00 1970 From: george.dunlap@eu.citrix.com (George Dunlap) Date: Thu, 16 Apr 2015 09:56:22 +0100 Subject: [Xen-devel] "tcp: refine TSO autosizing" causes performance regression on Xen In-Reply-To: <1429121979.7346.138.camel@edumazet-glaptop2.roam.corp.google.com> References: <1428596218.25985.263.camel@edumazet-glaptop2.roam.corp.google.com> <1428932970.3834.4.camel@edumazet-glaptop2.roam.corp.google.com> <1429115934.7346.107.camel@edumazet-glaptop2.roam.corp.google.com> <552E9E8D.1080000@eu.citrix.com> <1429118948.7346.114.camel@edumazet-glaptop2.roam.corp.google.com> <552EA2BC.5000707@eu.citrix.com> <1429120373.7346.125.camel@edumazet-glaptop2.roam.corp.google.com> <552EA844.5010308@eu.citrix.com> <1429121979.7346.138.camel@edumazet-glaptop2.roam.corp.google.com> Message-ID: <552F7936.9070205@eu.citrix.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 04/15/2015 07:19 PM, Eric Dumazet wrote: > On Wed, 2015-04-15 at 19:04 +0100, George Dunlap wrote: > >> Maybe you should stop wasting all of our time and just tell us what >> you're thinking. > > I think you make me wasting my time. > > I already gave all the hints in prior discussions. Right, and I suggested these two options: "Obviously one solution would be to allow the drivers themselves to set the tcp_limit_output_bytes, but that seems like a maintenance nightmare. "Another simple solution would be to allow drivers to indicate whether they have a high transmit latency, and have the kernel use a higher value by default when that's the case." [1] Neither of which you commented on. Instead you pointed me to a comment that only partially described what the limitations were. (I.e., it described the "two packets or 1ms", but not how they related, nor how they related to the "max of 2 64k packets outstanding" of the default tcp_limit_output_bytes setting.) -George [1] http://marc.info/?i=