On 2016-07-13 09:57, Dave Taht wrote: > On Tue, Jul 12, 2016 at 4:02 PM, Dave Taht <dave.taht@xxxxxxxxx> wrote: >> On Tue, Jul 12, 2016 at 3:21 PM, Felix Fietkau <nbd@xxxxxxxx> wrote: >>> On 2016-07-12 14:13, Dave Taht wrote: >>>> On Tue, Jul 12, 2016 at 12:09 PM, Felix Fietkau <nbd@xxxxxxxx> wrote: >>>>> Hi, >>>>> >>>>> With Toke's ath9k txq patch I've noticed a pretty nasty performance >>>>> regression when running local iperf on an AP (running the txq stuff) to >>>>> a wireless client. >>>> >>>> Your kernel? cpu architecture? >>> QCA9558, 720 MHz, running Linux 4.4.14 > > So this is a single core at the near-bottom end of the range. I guess > we also should find a MIPS 24c derivative that runs at 400Mhz or so. > > What HZ? (I no longer know how much higher HZ settings make any > difference, but I'm usually at NOHZ and 250, rather than 100.) > > And all the testing to date was on much higher end multi-cores. > >>>> What happens when going through the AP to a server from the wireless client? >>> Will test that next. > > Anddddd? Single stream: 130 Mbit/s, 70% idle Two streams: 50-80 Mbit/s (wildly fluctuating), 73% idle. >>>> Which direction? >>> AP->STA, iperf running on the AP. Client is a regular MacBook Pro >>> (Broadcom). >> >> There are always 2 wifi chips in play. Like the Sith. >> >>>>> Here's some things that I found: >>>>> - when I use only one TCP stream I get around 90-110 Mbit/s >>>> >>>> with how much cpu left over? >>> ~20% >>> >>>>> - when running multiple TCP streams, I get only 35-40 Mbit/s total >>>> with how much cpu left over? >>> ~30% > > To me this implies a contending lock issue, too much work in the irq > handler or too delayed work in the softirq handler.... > > I thought you were very brave to try and backport this. I don't think this has anything to do with contending locks, CPU utilization, etc. The code does something to the packets that TCP really doesn't like. - Felix -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
