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From:   Vineeth Remanan Pillai <vpillai@digitalocean.com>
Date:   Tue, 14 Jan 2020 10:40:31 -0500
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Subject: Re: [RFC PATCH v4 00/19] Core scheduling v4
To:     Tim Chen <tim.c.chen@linux.intel.com>
Cc:     Nishanth Aravamudan <naravamudan@digitalocean.com>,
        Julien Desfossez <jdesfossez@digitalocean.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Paul Turner <pjt@google.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
        Dario Faggioli <dfaggioli@suse.com>,
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        Aaron Lu <aaron.lwe@gmail.com>,
        Aubrey Li <aubrey.intel@gmail.com>,
        Valentin Schneider <valentin.schneider@arm.com>,
        Mel Gorman <mgorman@techsingularity.net>,
        Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
        Paolo Bonzini <pbonzini@redhat.com>
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On Mon, Jan 13, 2020 at 8:12 PM Tim Chen <tim.c.chen@linux.intel.com> wrote:

> I also encountered kernel panic with the v4 code when taking cpu offline or online
> when core scheduler is running.  I've refreshed the previous patch, along
> with 3 other patches to fix problems related to CPU online/offline.
>
> As a side effect of the fix, each core can now operate in core-scheduling
> mode or non core-scheduling mode, depending on how many online SMT threads it has.
>
> Vineet, are you guys planning to refresh v4 and update it to v5?  Aubrey posted
> a port to the latest kernel earlier.
>
Thanks for the updated patch Tim.

We have been testing with v4 rebased on 5.4.8 as RC kernels had given us
trouble in the past. v5 is due soon and we are planning to release v5 when
5.5 comes out. As of now, v5 has your crash fixes and Aubrey's changes
related to load balancing. We are investigating a performance issue with
high overcommit io intensive workload and also we are trying to see if
we can add synchronization during VMEXITs so that a guest vm cannot run
run alongside with host kernel. We also need to think about the userland
interface for corescheduling in preparation for upstreaming work.

Does it make sense to wait until 5.5 release for v5 considering the
above details?

Thanks,
Vineeth