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SubjectRE: [PATCH] clocksource/drivers/arc_timer: Utilize generic sched_clock
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Hi Vineet,

> -----Original Message-----
> From: Vineet Gupta
> Sent: Tuesday, October 16, 2018 7:03 PM
> To: Alexey Brodkin <abrodkin@synopsys.com>; linux-kernel@vger.kernel.org
> Cc: linux-snps-arc@lists.infradead.org; Daniel Lezcano <daniel.lezcano@linaro.org>; Thomas Gleixner <tglx@linutronix.de>
> Subject: Re: [PATCH] clocksource/drivers/arc_timer: Utilize generic sched_clock
>
> On 10/16/2018 12:45 AM, Alexey Brodkin wrote:
> > It turned out we used to use default implementation of sched_clock()
> > from kernel/sched/clock.c which was as precise as 1/HZ, i.e.
> > by default we had 10 msec granularity of time measurement.
> >
> > Now given ARC built-in timers are clocked with the same frequency as
> > CPU cores we may get much higher precision of time tracking.
>
> Can you do LMBench runs with and w/o and see if there's any other changes. I'm
> hoping lat_ctx will be more consistent.

Sure, I have this, see below:
========================================================
L M B E N C H 3 . 0 S U M M A R Y
------------------------------------
(Alpha software, do not distribute)

Basic system parameters
--------------------------------------------------------------------------------------
Host OS Description Mhz tlb cache mem scal
pages line par load
bytes
----------------- ------------- --------------------------------------- ---- ----- ----- ------ ----
hz-2018.10.16.log Linux 4.18.14 hz-2018.10.16.log 998 8 128 1.7500 1
sched_clock-2018. Linux 4.18.14 sched_clock-2018.10.16.log 997 8 1.7500 1

Processor, Processes - times in microseconds - smaller is better
------------------------------------------------------------------------------
Host OS Mhz null null open slct sig sig fork exec sh
call I/O stat clos TCP inst hndl proc proc proc
--------- ------------- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ----
hz-2018.1 Linux 4.18.14 998 0.38 0.59 2.76 5.02 22.4 0.54 2.23 319. 1780 3347
sched_clo Linux 4.18.14 997 0.38 0.61 2.66 5.01 22.3 0.54 2.25 325. 1775 3315

Basic integer operations - times in nanoseconds - smaller is better
-------------------------------------------------------------------
Host OS intgr intgr intgr intgr intgr
bit add mul div mod
--------- ------------- ------ ------ ------ ------ ------
hz-2018.1 Linux 4.18.14 1.0100 1.1500 13.0 7.9900
sched_clo Linux 4.18.14 1.0100 1.1500 13.0 7.9900

Basic uint64 operations - times in nanoseconds - smaller is better
------------------------------------------------------------------
Host OS int64 int64 int64 int64 int64
bit add mul div mod
--------- ------------- ------ ------ ------ ------ ------
hz-2018.1 Linux 4.18.14 11. 10.2 126.2 96.5
sched_clo Linux 4.18.14 11. 10.2 126.2 96.6

Basic float operations - times in nanoseconds - smaller is better
-----------------------------------------------------------------
Host OS float float float float
add mul div bogo
--------- ------------- ------ ------ ------ ------
hz-2018.1 Linux 4.18.14 184.5 181.5 375.0 935.3
sched_clo Linux 4.18.14 185.1 185.7 375.0 882.9

Basic double operations - times in nanoseconds - smaller is better
------------------------------------------------------------------
Host OS double double double double
add mul div bogo
--------- ------------- ------ ------ ------ ------
hz-2018.1 Linux 4.18.14 253.9 285.6 1490.0 2264.3
sched_clo Linux 4.18.14 255.0 283.6 1515.0 2284.3

Context switching - times in microseconds - smaller is better
-------------------------------------------------------------------------
Host OS 2p/0K 2p/16K 2p/64K 8p/16K 8p/64K 16p/16K 16p/64K
ctxsw ctxsw ctxsw ctxsw ctxsw ctxsw ctxsw
--------- ------------- ------ ------ ------ ------ ------ ------- -------
hz-2018.1 Linux 4.18.14 3.4400 6.7700 0.7300 9.6300 68.1 15.3 115.0
sched_clo Linux 4.18.14 3.5100 7.1300 5.7900 7.9200 71.8 17.6 124.5

*Local* Communication latencies in microseconds - smaller is better
---------------------------------------------------------------------
Host OS 2p/0K Pipe AF UDP RPC/ TCP RPC/ TCP
ctxsw UNIX UDP TCP conn
--------- ------------- ----- ----- ---- ----- ----- ----- ----- ----
hz-2018.1 Linux 4.18.14 3.440 14.6 16.0 31.5 48.0 94.
sched_clo Linux 4.18.14 3.510 15.5 13.4 31.5 49.4 158.

*Remote* Communication latencies in microseconds - smaller is better
---------------------------------------------------------------------
Host OS UDP RPC/ TCP RPC/ TCP
UDP TCP conn
--------- ------------- ----- ----- ----- ----- ----
hz-2018.1 Linux 4.18.14
sched_clo Linux 4.18.14

File & VM system latencies in microseconds - smaller is better
-------------------------------------------------------------------------------
Host OS 0K File 10K File Mmap Prot Page 100fd
Create Delete Create Delete Latency Fault Fault selct
--------- ------------- ------ ------ ------ ------ ------- ----- ------- -----
hz-2018.1 Linux 4.18.14 11.0 7.8438 54.3 12.8 221.0 0.475 1.16420 8.607
sched_clo Linux 4.18.14 10.8 7.7240 54.1 12.9 223.0 0.505 1.16280 8.475

*Local* Communication bandwidths in MB/s - bigger is better
-----------------------------------------------------------------------------
Host OS Pipe AF TCP File Mmap Bcopy Bcopy Mem Mem
UNIX reread reread (libc) (hand) read write
--------- ------------- ---- ---- ---- ------ ------ ------ ------ ---- -----
hz-2018.1 Linux 4.18.14 224. 456. 111. 248.0 404.8 384.6 232.4 405. 454.4
sched_clo Linux 4.18.14 220. 458. 145. 241.6 404.6 384.3 232.3 404. 453.9

Memory latencies in nanoseconds - smaller is better
(WARNING - may not be correct, check graphs)
------------------------------------------------------------------------------
Host OS Mhz L1 $ L2 $ Main mem Rand mem Guesses
--------- ------------- --- ---- ---- -------- -------- -------
hz-2018.1 Linux 4.18.14 998 3.0820 24.3 210.5 371.0
sched_clo Linux 4.18.14 997 3.0820 24.3 210.6 371.2
========================================================

> > diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> > index dec0dd88ec15..3268dad4effe 100644
> > --- a/drivers/clocksource/Kconfig
> > +++ b/drivers/clocksource/Kconfig
> > @@ -290,6 +290,7 @@ config CLKSRC_MPS2
> >
> > config ARC_TIMERS
> > bool "Support for 32-bit TIMERn counters in ARC Cores" if COMPILE_TEST
> > + depends on GENERIC_SCHED_CLOCK
>
> It needs to select, not depends on

Well from what I may see git grepping:
1) Architcture selects GENERIC_SCHED_CLOCK
2) Clocksource driver depends on GENERIC_SCHED_CLOCK

> > @@ -88,6 +89,11 @@ static u64 arc_read_gfrc(struct clocksource *cs)
> > return (((u64)h) << 32) | l;
> > }
> >
> > +static u64 arc_gfrc_clock_read(void)
>
> Needs to be notrace like other such routines.

Ok will add this.

> >
> > +
> > static struct clocksource arc_counter_timer1 = {
> > .name = "ARC Timer1",
> > .rating = 300,
> > @@ -209,6 +229,8 @@ static int __init arc_cs_setup_timer1(struct device_node *node)
> > write_aux_reg(ARC_REG_TIMER1_CNT, 0);
> > write_aux_reg(ARC_REG_TIMER1_CTRL, TIMER_CTRL_NH);
> >
> > + sched_clock_register(arc_timer1_clock_read, 64, arc_timer_freq);
>
> TIMER1 is 32 bits wide.

Yep , blind copy-pasting is not good, will change it.

-Alexey

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