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Date:   Tue, 12 Sep 2023 13:33:56 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Ankur Arora <ankur.a.arora@oracle.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org,
        akpm@linux-foundation.org, luto@kernel.org, bp@alien8.de,
        dave.hansen@linux.intel.com, hpa@zytor.com, mingo@redhat.com,
        juri.lelli@redhat.com, vincent.guittot@linaro.org, mgorman@suse.de,
        rostedt@goodmis.org, tglx@linutronix.de, jon.grimm@amd.com,
        bharata@amd.com, raghavendra.kt@amd.com,
        boris.ostrovsky@oracle.com, konrad.wilk@oracle.com,
        jgross@suse.com, andrew.cooper3@citrix.com
Subject: Re: [PATCH v2 7/9] sched: define TIF_ALLOW_RESCHED
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On Tue, Sep 12, 2023 at 10:26:06AM +0200, Peter Zijlstra wrote:
> > How expensive would be always having PREEMPT_COUNT=y?
> 
> Effectively I think that is true today. At the very least Debian and
> SuSE (I can't find a RHEL .config in a hurry but I would think they too)
> ship with PREEMPT_DYNAMIC=y.

$ grep PREEMPT uek-rpm/ol9/config-x86_64
# CONFIG_PREEMPT_NONE is not set
CONFIG_PREEMPT_VOLUNTARY=y
# CONFIG_PREEMPT is not set
CONFIG_HAVE_PREEMPT_DYNAMIC=y
CONFIG_PREEMPT_NOTIFIERS=y
CONFIG_DRM_I915_PREEMPT_TIMEOUT=640
# CONFIG_PREEMPTIRQ_DELAY_TEST is not set

$ grep PREEMPT uek-rpm/ol9/config-aarch64
# CONFIG_PREEMPT_NONE is not set
CONFIG_PREEMPT_VOLUNTARY=y
# CONFIG_PREEMPT is not set
CONFIG_PREEMPT_NOTIFIERS=y
# CONFIG_PREEMPTIRQ_DELAY_TEST is not set