linux-kernel - [PATCH v2 0/2] sched: blk: Handle HMP systems when completing IO

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Date: Fri, 23 Feb 2024 15:57:47 +0000
From: Qais Yousef <qyousef@...alina.io>
To: Jens Axboe <axboe@...nel.dk>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>
Cc: linux-kernel@...r.kernel.org,
	linux-block@...r.kernel.org,
	Sudeep Holla <sudeep.holla@....com>,
	Wei Wang <wvw@...gle.com>,
	Jaegeuk Kim <jaegeuk@...nel.org>,
	Bart Van Assche <bvanassche@....org>,
	Christoph Hellwig <hch@...radead.org>,
	Qais Yousef <qyousef@...alina.io>
Subject: [PATCH v2 0/2] sched: blk: Handle HMP systems when completing IO

Due to recent changes in how topology is represented on asymmetric multi
processing systems like big.LITTLE where all cpus share the last LLC, there is
a performance regression as cpus with different compute capacities appear under
the same LLC and we no longer send an IPI when the requester is running on
a different cluster with different compute capacity.

Restore the old behavior by adding a new cpus_equal_capacity() function to help
check for the new condition for these systems.

Changes since v1:

	* Split the patch per subsystem.
	* Convert cpus_gte_capacity() to cpus_equal_capacity()
	* Make cpus_equal_capacity() return immediately for SMP systems.

Qais Yousef (2):
  sched: Add a new function to compare if two cpus have the same
    capacity
  block/blk-mq: Don't complete locally if capacities are different

 block/blk-mq.c                 |  5 +++--
 include/linux/sched/topology.h |  6 ++++++
 kernel/sched/core.c            | 11 +++++++++++
 3 files changed, 20 insertions(+), 2 deletions(-)

-- 
2.34.1