From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EC65233EC for ; Mon, 16 Jan 2023 15:59:03 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 73155C433D2; Mon, 16 Jan 2023 15:59:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1673884743; bh=FSzIl3Br0IRJ4e/YjR2XgmqTQrKkFeAFEIh8XT+PnGc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=nRdWWNxJnVljO8AMPDv9noenAbfHVihdnzv2lNynTWnfCCWkKsWawNE6sDdpc0/Ot 1iNywmbI/LHlWmigPkfwgQY1aXstWwU6/f3I/AVRHLDiHDp8C421QetTl2E+BR5o7b wIgCy9g19v0zGc6hOJHYWMrnYNw+NnwFUsE2655U= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "Peter Zijlstra (Intel)" , Yair Podemsky , Ingo Molnar , Valentin Schneider , Giovanni Gherdovich , Sasha Levin Subject: [PATCH 6.1 122/183] sched/core: Fix arch_scale_freq_tick() on tickless systems Date: Mon, 16 Jan 2023 16:50:45 +0100 Message-Id: <20230116154808.552935737@linuxfoundation.org> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230116154803.321528435@linuxfoundation.org> References: <20230116154803.321528435@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Yair Podemsky [ Upstream commit 7fb3ff22ad8772bbf0e3ce1ef3eb7b09f431807f ] In order for the scheduler to be frequency invariant we measure the ratio between the maximum CPU frequency and the actual CPU frequency. During long tickless periods of time the calculations that keep track of that might overflow, in the function scale_freq_tick(): if (check_shl_overflow(acnt, 2*SCHED_CAPACITY_SHIFT, &acnt)) goto error; eventually forcing the kernel to disable the feature for all CPUs, and show the warning message: "Scheduler frequency invariance went wobbly, disabling!". Let's avoid that by limiting the frequency invariant calculations to CPUs with regular tick. Fixes: e2b0d619b400 ("x86, sched: check for counters overflow in frequency invariant accounting") Suggested-by: "Peter Zijlstra (Intel)" Signed-off-by: Yair Podemsky Signed-off-by: Ingo Molnar Reviewed-by: Valentin Schneider Acked-by: Giovanni Gherdovich Link: https://lore.kernel.org/r/20221130125121.34407-1-ypodemsk@redhat.com Signed-off-by: Sasha Levin --- kernel/sched/core.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 981e41cc4121..172ec79b66f6 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5498,7 +5498,9 @@ void scheduler_tick(void) unsigned long thermal_pressure; u64 resched_latency; - arch_scale_freq_tick(); + if (housekeeping_cpu(cpu, HK_TYPE_TICK)) + arch_scale_freq_tick(); + sched_clock_tick(); rq_lock(rq, &rf); -- 2.35.1