linux-kernel - Re: [PATCH 0/2] pseries/hotplug: Change the default behaviour of cede

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Message-ID: <874l19r0pw.fsf@linux.ibm.com>
Date:   Wed, 18 Sep 2019 12:08:43 -0500
From:   Nathan Lynch <nathanl@...ux.ibm.com>
To:     Gautham R Shenoy <ego@...ux.vnet.ibm.com>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
        Kamalesh Babulal <kamaleshb@...ibm.com>,
        "Naveen N . Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        Tyrel Datwyler <tyreld@...ux.ibm.com>
Subject: Re: [PATCH 0/2] pseries/hotplug: Change the default behaviour of cede_offline

Gautham R Shenoy <ego@...ux.vnet.ibm.com> writes:
> The accounting problem in tools such as lparstat with
> "cede_offline=on" is affecting customers who are using these tools for
> capacity-planning. That problem needs a fix in the short-term, for
> which Patch 1 changes the default behaviour of cede_offline from "on"
> to "off". Since this patch would break the existing userspace tools
> that use the CPU-Offline infrastructure to fold CPUs for saving power,
> the sysfs interface allowing a runtime change of cede_offline_enabled
> was provided to enable these userspace tools to cope with minimal
> change.

So we would be putting users in the position of choosing between folding
and correct accounting. :-(

Actually how does changing the offline mechanism to stop-self break the
folding utility?