From: Peter Zijlstra <peterz@infradead.org>
To: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>,
K Prateek Nayak <kprateek.nayak@amd.com>,
"Gautham R . Shenoy" <gautham.shenoy@amd.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Juri Lelli <juri.lelli@redhat.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Valentin Schneider <vschneid@redhat.com>,
Madadi Vineeth Reddy <vineethr@linux.ibm.com>,
Hillf Danton <hdanton@sina.com>,
Shrikanth Hegde <sshegde@linux.ibm.com>,
Jianyong Wu <jianyong.wu@outlook.com>,
Yangyu Chen <cyy@cyyself.name>,
Tingyin Duan <tingyin.duan@gmail.com>,
Vern Hao <vernhao@tencent.com>, Vern Hao <haoxing990@gmail.com>,
Len Brown <len.brown@intel.com>, Aubrey Li <aubrey.li@intel.com>,
Zhao Liu <zhao1.liu@intel.com>, Chen Yu <yu.chen.surf@gmail.com>,
Chen Yu <yu.c.chen@intel.com>,
Adam Li <adamli@os.amperecomputing.com>,
Aaron Lu <ziqianlu@bytedance.com>,
Tim Chen <tim.c.chen@intel.com>, Josh Don <joshdon@google.com>,
Gavin Guo <gavinguo@igalia.com>,
Qais Yousef <qyousef@layalina.io>,
Libo Chen <libchen@purestorage.com>,
linux-kernel@vger.kernel.org
Subject: Re: [Patch v4 01/22] sched/cache: Introduce infrastructure for cache-aware load balancing
Date: Fri, 10 Apr 2026 01:00:04 +0200 [thread overview]
Message-ID: <20260409230004.GV2872@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <71b4ddab042b805a225eef92b0a9404b20aa2b98.camel@linux.intel.com>
On Thu, Apr 09, 2026 at 12:21:58PM -0700, Tim Chen wrote:
> > > + get_nr_threads(p) <= 1) {
> >
> > And this, I just noticed this, why are we excluding tasks with one
> > thread? The comment just states we are (doh), but utterly fails to
> > explain why.
>
> The thought was that for a single thread, we will tend to place it
> in same LLC as it was previously running with cache hot. Incurring
> the added cost of tracking its residency in LLC is uneeded.
Not sure -- the moment it gets migrated away, it will stay away. There
is no force to pull it back, while with cache aware it will try and come
back for a short while -- until it's build an occupancy on the new llc.
Anyway, if you want to do this, it needs to be a separate patch.
next prev parent reply other threads:[~2026-04-09 23:00 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-01 21:52 [Patch v4 00/22] Cache aware scheduling Tim Chen
2026-04-01 21:52 ` [Patch v4 01/22] sched/cache: Introduce infrastructure for cache-aware load balancing Tim Chen
2026-04-09 12:41 ` Peter Zijlstra
2026-04-09 19:21 ` Tim Chen
2026-04-09 23:00 ` Peter Zijlstra [this message]
2026-04-10 6:30 ` Chen, Yu C
2026-04-15 2:06 ` Vern Hao
2026-04-15 3:34 ` Chen, Yu C
2026-04-01 21:52 ` [Patch v4 02/22] sched/cache: Limit the scan number of CPUs when calculating task occupancy Tim Chen
2026-04-09 13:17 ` Luo Gengkun
2026-04-09 13:41 ` Peter Zijlstra
2026-04-10 10:12 ` Luo Gengkun
2026-04-10 7:29 ` Chen, Yu C
2026-04-10 10:20 ` Luo Gengkun
2026-04-10 17:12 ` Tim Chen
2026-04-10 17:27 ` Chen, Yu C
2026-04-13 7:23 ` [RFC PATCH] sched/fair: dynamically scale the period of cache work Jianyong Wu
2026-04-13 8:38 ` Chen, Yu C
2026-04-13 11:27 ` Jianyong Wu
2026-04-15 3:31 ` Chen, Yu C
2026-04-16 3:39 ` Jianyong Wu
2026-04-15 17:22 ` Tim Chen
2026-04-16 6:50 ` Jianyong Wu
2026-04-14 15:07 ` [PATCH v2] sched/cache: Reduce the overhead of task_cache_work by only scan the visisted cpus Luo Gengkun
2026-04-15 3:10 ` Chen, Yu C
2026-04-18 9:01 ` Luo Gengkun
2026-04-20 7:53 ` Chen, Yu C
2026-04-23 8:54 ` [PATCH v3] " Luo Gengkun
2026-04-01 21:52 ` [Patch v4 03/22] sched/cache: Record per LLC utilization to guide cache aware scheduling decisions Tim Chen
2026-04-01 21:52 ` [Patch v4 04/22] sched/cache: Introduce helper functions to enforce LLC migration policy Tim Chen
2026-04-01 21:52 ` [Patch v4 05/22] sched/cache: Make LLC id continuous Tim Chen
2026-04-01 21:52 ` [Patch v4 06/22] sched/cache: Assign preferred LLC ID to processes Tim Chen
2026-04-01 21:52 ` [Patch v4 07/22] sched/cache: Track LLC-preferred tasks per runqueue Tim Chen
2026-04-01 21:52 ` [Patch v4 08/22] sched/cache: Introduce per CPU's tasks LLC preference counter Tim Chen
2026-04-01 21:52 ` [Patch v4 09/22] sched/cache: Calculate the percpu sd task LLC preference Tim Chen
2026-04-01 21:52 ` [Patch v4 10/22] sched/cache: Count tasks prefering destination LLC in a sched group Tim Chen
2026-04-01 21:52 ` [Patch v4 11/22] sched/cache: Check local_group only once in update_sg_lb_stats() Tim Chen
2026-04-01 21:52 ` [Patch v4 12/22] sched/cache: Prioritize tasks preferring destination LLC during balancing Tim Chen
2026-04-01 21:52 ` [Patch v4 13/22] sched/cache: Add migrate_llc_task migration type for cache-aware balancing Tim Chen
2026-04-01 21:52 ` [Patch v4 14/22] sched/cache: Handle moving single tasks to/from their preferred LLC Tim Chen
2026-04-01 21:52 ` [Patch v4 15/22] sched/cache: Respect LLC preference in task migration and detach Tim Chen
2026-04-01 21:52 ` [Patch v4 16/22] sched/cache: Disable cache aware scheduling for processes with high thread counts Tim Chen
2026-04-09 12:43 ` Peter Zijlstra
2026-04-09 19:27 ` Tim Chen
2026-04-01 21:52 ` [Patch v4 17/22] sched/cache: Avoid cache-aware scheduling for memory-heavy processes Tim Chen
2026-04-09 12:46 ` Peter Zijlstra
2026-04-09 12:55 ` Peter Zijlstra
2026-04-10 8:59 ` Chen, Yu C
2026-04-10 9:20 ` Peter Zijlstra
2026-04-01 21:52 ` [Patch v4 18/22] sched/cache: Enable cache aware scheduling for multi LLCs NUMA node Tim Chen
2026-04-09 13:37 ` Peter Zijlstra
2026-04-09 19:39 ` Tim Chen
2026-04-01 21:52 ` [Patch v4 19/22] sched/cache: Allow the user space to turn on and off cache aware scheduling Tim Chen
2026-04-01 21:52 ` [Patch v4 20/22] sched/cache: Add user control to adjust the aggressiveness of cache-aware scheduling Tim Chen
2026-04-01 21:52 ` [Patch v4 21/22] -- DO NOT APPLY!!! -- sched/cache/debug: Display the per LLC occupancy for each process via proc fs Tim Chen
2026-04-01 21:52 ` [Patch v4 22/22] -- DO NOT APPLY!!! -- sched/cache/debug: Add ftrace to track the load balance statistics Tim Chen
2026-04-09 13:54 ` [Patch v4 00/22] Cache aware scheduling Peter Zijlstra
2026-04-09 20:02 ` Tim Chen
2026-04-14 3:20 ` Duan Tingyin
2026-04-15 17:35 ` Tim Chen
2026-04-16 0:27 ` Qais Yousef
2026-04-20 9:01 ` Chen, Yu C
2026-04-21 0:34 ` Qais Yousef
2026-04-21 20:57 ` Tim Chen
2026-04-23 15:06 ` Qais Yousef
2026-04-23 16:48 ` Chen, Yu C
2026-04-25 0:05 ` Qais Yousef
2026-04-23 17:17 ` Chen, Yu C
2026-04-25 0:14 ` Qais Yousef
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