linux-kernel - Re: [PATCH 00/19] Cache Aware Scheduling

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Message-ID: <7cacde40-153b-4814-8460-0805f1eb7bdb@intel.com>
Date: Thu, 16 Oct 2025 12:57:04 +0800
From: "Chen, Yu C" <yu.c.chen@...el.com>
To: Madadi Vineeth Reddy <vineethr@...ux.ibm.com>
CC: Tim Chen <tim.c.chen@...ux.intel.com>, Peter Zijlstra
	<peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, K Prateek Nayak
	<kprateek.nayak@....com>, "Gautham R . Shenoy" <gautham.shenoy@....com>,
	Vincent Guittot <vincent.guittot@...aro.org>, Juri Lelli
	<juri.lelli@...hat.com>, Dietmar Eggemann <dietmar.eggemann@....com>, "Steven
 Rostedt" <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, Mel Gorman
	<mgorman@...e.de>, Valentin Schneider <vschneid@...hat.com>, Hillf Danton
	<hdanton@...a.com>, Shrikanth Hegde <sshegde@...ux.ibm.com>, Jianyong Wu
	<jianyong.wu@...look.com>, Yangyu Chen <cyy@...self.name>, Tingyin Duan
	<tingyin.duan@...il.com>, Vern Hao <vernhao@...cent.com>, Len Brown
	<len.brown@...el.com>, Aubrey Li <aubrey.li@...el.com>, Zhao Liu
	<zhao1.liu@...el.com>, Chen Yu <yu.chen.surf@...il.com>, Adam Li
	<adamli@...amperecomputing.com>, Tim Chen <tim.c.chen@...el.com>,
	<linux-kernel@...r.kernel.org>, <haoxing990@...il.com>
Subject: Re: [PATCH 00/19] Cache Aware Scheduling

On 10/16/2025 2:26 AM, Madadi Vineeth Reddy wrote:
> On 15/10/25 11:08, Chen, Yu C wrote:
>> On 10/15/2025 5:48 AM, Tim Chen wrote:
>>> On Tue, 2025-10-14 at 17:43 +0530, Madadi Vineeth Reddy wrote:
>>>> Hi Tim,
>>>> Thanks for the patch.
>>>>
>>>> On 11/10/25 23:54, Tim Chen wrote:

[snip]

>>>> ChaCha20-xiangshan improvement in Genoa when llc_aggr_tolerance is set to 100 seems
>>>> due to having relatively lesser thread count. Please provide the numbers
>>>> with default values too. Would like to know numbers on varying loads.
>>>
>>> I'll ask Chen Yu who did the Xiangshan experiments if he has those numbers.
>>>
>>
>> Madadi, do you mean the performance score number or active thread number
>>   when llc_aggr_tolerance is set to 1(default)?
>> The score is around with sched_cache and llc_aggr_tolerance set to 1.
>> The active number is 128 per process, and there are 8 processes when
>> launching the benchmark. I suppose the 128 comes from the number
>> of online CPUs. Please let me know if you need more data.
>>
>> Cced Yangyu who's the author of this benchmark.
> 
> I mean the benchmark result with default value of llc_aggr_tolerance on Genoa
> in comparison to baseline. Knowing number of threads also helps to understand
> the impact.
> 

OK. Here are the full test script and corresponding data:
pepc pstates config --governor performance
pepc pstates config --turbo off
pepc cstates config --disable C2
echo 1 > /proc/sys/kernel/numa_balancing

echo NO_SCHED_CACHE > /sys/kernel/debug/sched/features
make run
sleep 5
sync

echo SCHED_CACHE > /sys/kernel/debug/sched/features
echo 50 > /sys/kernel/debug/sched/llc_overload_pct
echo 1 > /sys/kernel/debug/sched/llc_aggr_tolerance
make run

echo SCHED_CACHE > /sys/kernel/debug/sched/features
# to encourage task aggregation as much as possible
echo 100 > /sys/kernel/debug/sched/llc_overload_pct
echo 100 > /sys/kernel/debug/sched/llc_aggr_tolerance
make run


# ./launch.sh

Host time spent: 51,323ms //baseline
Host time spent: 51,741ms //sched_cache default
Host time spent: 27,934ms //sched_cache aggressive

thanks,
Chenyu