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Date: Sat, 4 Jul 2015 11:40:11 +0800
From: Jisheng Zhang <jszhang@...vell.com>
To: Daniel Lezcano <daniel.lezcano@...aro.org>
CC: <tglx@...utronix.de>, <linux-kernel@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] clocksource: dw_apb_timer: add dynamic irq flag to the
timer
Dear Daniel,
On Fri, 3 Jul 2015 16:58:44 +0200
Daniel Lezcano <daniel.lezcano@...aro.org> wrote:
> On 07/03/2015 04:30 PM, Jisheng Zhang wrote:
> > Commit d2348fb6fdc6 ("tick: Dynamically set broadcast irq affinity")
> > adds one excelent feature CLOCK_EVT_FEAT_DYNIRQ to let the core set the
> > interrupt affinity of the broadcast interrupt to the cpu which has the
> > earliest expiry time. This patch adds CLOCK_EVT_FEAT_DYNIRQ flag to
> > avoid unnecessary wakeups and IPIs when the dw_apb_timer is used as
> > broadcast timer.
> >
> > Signed-off-by: Jisheng Zhang <jszhang@...vell.com>
> > ---
>
> I am glad this flag helps. Were you able to do some measurements ?
Sure. Here is the rough measurement step:
~ # rm /tmp/test.sh
~ # cat > /tmp/test.sh
cat /proc/interrupts
for i in `seq 10` ; do sleep $i; done
cat /proc/interrupts
~ # chmod +x /tmp/test.sh
~ # taskset 0x2 /tmp/test.sh
without the patch:
CPU0 CPU1
27: 115 36 GIC 27 arch_timer
45: 62 0 GIC 45 mmc0
160: 88 0 interrupt-controller 8 timer
227: 0 0 interrupt-controller 4 f7e81400.i2c
228: 0 0 interrupt-controller 5 f7e81800.i2c
229: 0 0 interrupt-controller 7 dw_spi65535
230: 0 0 interrupt-controller 21 f7e84000.i2c
231: 0 0 interrupt-controller 20 f7e84800.i2c
265: 445 0 interrupt-controller 8 serial
IPI0: 0 0 CPU wakeup interrupts
IPI1: 0 11 Timer broadcast interrupts
IPI2: 56 104 Rescheduling interrupts
IPI3: 0 0 Function call interrupts
IPI4: 0 4 Single function call interrupts
IPI5: 0 0 CPU stop interrupts
IPI6: 25 27 IRQ work interrupts
IPI7: 0 0 completion interrupts
IPI8: 0 0 CPU backtrace
Err: 0
CPU0 CPU1
27: 115 38 GIC 27 arch_timer
45: 62 0 GIC 45 mmc0
160: 160 0 interrupt-controller 8 timer
227: 0 0 interrupt-controller 4 f7e81400.i2c
228: 0 0 interrupt-controller 5 f7e81800.i2c
229: 0 0 interrupt-controller 7 dw_spi65535
230: 0 0 interrupt-controller 21 f7e84000.i2c
231: 0 0 interrupt-controller 20 f7e84800.i2c
265: 514 0 interrupt-controller 8 serial
IPI0: 0 0 CPU wakeup interrupts
IPI1: 0 83 Timer broadcast interrupts
IPI2: 56 104 Rescheduling interrupts
IPI3: 0 0 Function call interrupts
IPI4: 0 4 Single function call interrupts
IPI5: 0 0 CPU stop interrupts
IPI6: 25 46 IRQ work interrupts
IPI7: 0 0 completion interrupts
IPI8: 0 0 CPU backtrace
Err: 0
cpu0 get 160-88=72 timer interrupts, CPU1 got 83-11=72 broadcast timer IPIs
So, overall system got 72+72=144 wake ups and 72 broadcast timer IPIs
With the patch:
CPU0 CPU1
27: 107 37 GIC 27 arch_timer
45: 62 0 GIC 45 mmc0
160: 66 7 interrupt-controller 8 timer
227: 0 0 interrupt-controller 4 f7e81400.i2c
228: 0 0 interrupt-controller 5 f7e81800.i2c
229: 0 0 interrupt-controller 7 dw_spi65535
230: 0 0 interrupt-controller 21 f7e84000.i2c
231: 0 0 interrupt-controller 20 f7e84800.i2c
265: 311 0 interrupt-controller 8 serial
IPI0: 0 0 CPU wakeup interrupts
IPI1: 2 4 Timer broadcast interrupts
IPI2: 58 100 Rescheduling interrupts
IPI3: 0 0 Function call interrupts
IPI4: 0 4 Single function call interrupts
IPI5: 0 0 CPU stop interrupts
IPI6: 21 24 IRQ work interrupts
IPI7: 0 0 completion interrupts
IPI8: 0 0 CPU backtrace
Err: 0
CPU0 CPU1
27: 107 39 GIC 27 arch_timer
45: 62 0 GIC 45 mmc0
160: 69 75 interrupt-controller 8 timer
227: 0 0 interrupt-controller 4 f7e81400.i2c
228: 0 0 interrupt-controller 5 f7e81800.i2c
229: 0 0 interrupt-controller 7 dw_spi65535
230: 0 0 interrupt-controller 21 f7e84000.i2c
231: 0 0 interrupt-controller 20 f7e84800.i2c
265: 380 0 interrupt-controller 8 serial
IPI0: 0 0 CPU wakeup interrupts
IPI1: 3 6 Timer broadcast interrupts
IPI2: 60 100 Rescheduling interrupts
IPI3: 0 0 Function call interrupts
IPI4: 0 4 Single function call interrupts
IPI5: 0 0 CPU stop interrupts
IPI6: 21 45 IRQ work interrupts
IPI7: 0 0 completion interrupts
IPI8: 0 0 CPU backtrace
Err: 0
cpu0 got 69-66 = 3, cpu1 got 75-7=68 timer interrupts. cpu0 got 3-2 = 1
broadcast timer IPIs, cpu1 got 6-4=2 broadcast timer IPIs.
So, overall system got 3+68+1+2=74 wakeups and 1+2=3 broadcast timer IPIs
We removed 50% wakeups and almost 100% broadcast timer IPIs
I will add these rough measurement's result into the commit msg.
Thanks for your suggestion,
Jisheng
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