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From: "Song Bao Hua (Barry Song)" <song.bao.hua@hisilicon.com>
To: Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Vincent Guittot <vincent.guittot@linaro.org>
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Subject: RE: [RFC PATCH v6 3/4] scheduler: scan idle cpu in cluster for tasks within one LLC
Date: Fri, 7 May 2021 13:07:35 +0000
Message-ID: <aee3fd353a3a4bfca65aa1b78386f9b5@hisilicon.com> (raw)
In-Reply-To: <142c7192-cde8-6dbe-bb9d-f0fce21ec959@arm.com>



> -----Original Message-----
> From: Dietmar Eggemann [mailto:dietmar.eggemann@arm.com]
> Sent: Thursday, May 6, 2021 12:30 AM
> To: Song Bao Hua (Barry Song) <song.bao.hua@hisilicon.com>; Vincent Guittot
> <vincent.guittot@linaro.org>
> Cc: tim.c.chen@linux.intel.com; catalin.marinas@arm.com; will@kernel.org;
> rjw@rjwysocki.net; bp@alien8.de; tglx@linutronix.de; mingo@redhat.com;
> lenb@kernel.org; peterz@infradead.org; rostedt@goodmis.org;
> bsegall@google.com; mgorman@suse.de; msys.mizuma@gmail.com;
> valentin.schneider@arm.com; gregkh@linuxfoundation.org; Jonathan Cameron
> <jonathan.cameron@huawei.com>; juri.lelli@redhat.com; mark.rutland@arm.com;
> sudeep.holla@arm.com; aubrey.li@linux.intel.com;
> linux-arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org;
> linux-acpi@vger.kernel.org; x86@kernel.org; xuwei (O) <xuwei5@huawei.com>;
> Zengtao (B) <prime.zeng@hisilicon.com>; guodong.xu@linaro.org; yangyicong
> <yangyicong@huawei.com>; Liguozhu (Kenneth) <liguozhu@hisilicon.com>;
> linuxarm@openeuler.org; hpa@zytor.com
> Subject: Re: [RFC PATCH v6 3/4] scheduler: scan idle cpu in cluster for tasks
> within one LLC
> 
> On 03/05/2021 13:35, Song Bao Hua (Barry Song) wrote:
> 
> [...]
> 
> >> From: Song Bao Hua (Barry Song)
> 
> [...]
> 
> >>> From: Dietmar Eggemann [mailto:dietmar.eggemann@arm.com]
> 
> [...]
> 
> >>> On 29/04/2021 00:41, Song Bao Hua (Barry Song) wrote:
> >>>>
> >>>>
> >>>>> -----Original Message-----
> >>>>> From: Dietmar Eggemann [mailto:dietmar.eggemann@arm.com]
> >>>
> >>> [...]
> >>>
> >>>>>>>> From: Dietmar Eggemann [mailto:dietmar.eggemann@arm.com]
> >>>>>
> >>>>> [...]
> >>>>>
> >>>>>>>> On 20/04/2021 02:18, Barry Song wrote:
> 
> [...]
> 
> >
> > On the other hand, according to "sched: Implement smarter wake-affine logic"
> >
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/
> ?id=62470419
> >
> > Proper factor in wake_wide is mainly beneficial of 1:n tasks like
> postgresql/pgbench.
> > So using the smaller cluster size as factor might help make wake_affine false
> so
> > improve pgbench.
> >
> > From the commit log, while clients =  2*cpus, the commit made the biggest
> > improvement. In my case, It should be clients=48 for a machine whose LLC
> > size is 24.
> >
> > In Linux, I created a 240MB database and ran "pgbench -c 48 -S -T 20 pgbench"
> > under two different scenarios:
> > 1. page cache always hit, so no real I/O for database read
> > 2. echo 3 > /proc/sys/vm/drop_caches
> >
> > For case 1, using cluster_size and using llc_size will result in similar
> > tps= ~108000, all of 24 cpus have 100% cpu utilization.
> >
> > For case 2, using llc_size still shows better performance.
> >
> > tps for each test round(cluster size as factor in wake_wide):
> > 1398.450887 1275.020401 1632.542437 1412.241627 1611.095692 1381.354294
> 1539.877146
> > avg tps = 1464
> >
> > tps for each test round(llc size as factor in wake_wide):
> > 1718.402983 1443.169823 1502.353823 1607.415861 1597.396924 1745.651814
> 1876.802168
> > avg tps = 1641  (+12%)
> >
> > so it seems using cluster_size as factor in "slave >= factor && master >=
> slave *
> > factor" isn't a good choice for my machine at least.
> 
> So SD size = 4 (instead of 24) seems to be too small for `-c 48`.
> 
> Just curious, have you seen the benefit of using wake wide on SD size =
> 24 (LLC) compared to not using it at all?

At least in my benchmark made today, I have not seen any benefit to use
llc_size. Always returning 0 in wake_wide() seems to be much better.

postgres@ubuntu:$pgbench -i pgbench
postgres@pgbench:$ pgbench -T 120 -c 48 pgbench

using llc_size, it got to 123tps
always returning 0 in wake_wide(), it got to 158tps

actually, I really couldn't reproduce the performance improvement
the commit "sched: Implement smarter wake-affine logic" mentioned.
on the other hand, the commit log didn't present the pgbench command
parameter used. I guess the benchmark result will highly depend on
the command parameter and disk I/O speed.

Thanks
Barry


  reply index

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-20  0:18 [RFC PATCH v6 0/4] scheduler: expose the topology of clusters and add cluster scheduler Barry Song
2021-04-20  0:18 ` [RFC PATCH v6 1/4] topology: Represent clusters of CPUs within a die Barry Song
2021-04-28  9:48   ` Andrew Jones
2021-04-30  3:46     ` Song Bao Hua (Barry Song)
2021-04-20  0:18 ` [RFC PATCH v6 2/4] scheduler: add scheduler level for clusters Barry Song
2021-04-20  0:18 ` [RFC PATCH v6 3/4] scheduler: scan idle cpu in cluster for tasks within one LLC Barry Song
2021-04-27 11:35   ` Dietmar Eggemann
2021-04-28  9:51     ` Song Bao Hua (Barry Song)
2021-04-28 13:04       ` Vincent Guittot
2021-04-28 16:47         ` Dietmar Eggemann
     [not found]           ` <185746c4d02a485ca8f3509439328b26@hisilicon.com>
2021-04-30 10:42             ` Dietmar Eggemann
2021-05-03  6:19               ` Song Bao Hua (Barry Song)
2021-05-03 11:35               ` Song Bao Hua (Barry Song)
2021-05-05 12:29                 ` Dietmar Eggemann
2021-05-07 13:07                   ` Song Bao Hua (Barry Song) [this message]
2021-05-13 12:32                     ` Dietmar Eggemann
2021-05-25  8:14                       ` Song Bao Hua (Barry Song)
2021-05-26  9:54                       ` Song Bao Hua (Barry Song)
2021-04-20  0:18 ` [RFC PATCH v6 4/4] scheduler: Add cluster scheduler level for x86 Barry Song

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