From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 35E941C2DAD; Mon, 2 Sep 2024 09:21:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725268868; cv=none; b=YDwIl/KNLGWVN3AFyja8q5/m+/OENJE4RA6dIygeBXqeRh18naR/jwoYm3tWU6NAzvBPj1HDsn2KafK27KsLuZDpuoWxPsQBaj5KMQau6sou8tdaEchJ+cvO6+0fjTjaYMb6v066IBIwfyQ14nyHHyNjoBkugwc3eeKDDi3E1Ik= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725268868; c=relaxed/simple; bh=Xqc71HLB9RR0YC17nm4rIyYdKPMvk+koNamcsCl4XCU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=tcaNGz6IES9LMRvRh19Kh7yYsQxolB7Tfuqwpchi/M70PdQ9G5YO43radTUV75Vs7/+/msjithRq9I32QmVmWO473zwzx+xrDeA6k7w+rRzNG6qGwTKU1/Mgo3YEyvoDnqLBOzirMrI1mbfl65QSlkBrINDdzcR3VMBM94cDbmw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=ieipzoJd; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="ieipzoJd" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=JAulFDgx3FvNWuvmiwL6YUk4T1Qk0lgDdU6iJ9PrymU=; b=ieipzoJdht1lg4dRdhmixmOKYT TI1E8SwgNJhQ/iAsP/lACajYfGU6idk4EFzXg2saJgDFwVUGnVStqhfvs7LnWFDYjXAfU7CphCk7C TFJR/IS6aAY14y2ANY7hEWNZtxAxJv3uUbGv1V6nst7BXGky7h6uvkYTqosVt+zzmIhaRUuCY+r6V HRCTjbYjYQ1pt7ZWvlEe1raNGTy5uJMDh4ORyhGAWUSl2+B1FguKXNbU/3PYJjiD+1qNeDmL+g/lX 9SXEZyVfVfJfiuo2s3hTk+EQaq/OemlDBVUBy7YgXsGRMy2Il93jB2MWNA2SvjFXH1AUv3DLtMp7J lSFRbs4g==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.97.1 #2 (Red Hat Linux)) id 1sl3F0-0000000C7Yt-1IzZ; Mon, 02 Sep 2024 09:20:54 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id D9DAD300642; Mon, 2 Sep 2024 11:20:53 +0200 (CEST) Date: Mon, 2 Sep 2024 11:20:53 +0200 From: Peter Zijlstra To: Luo Gengkun Cc: mingo@redhat.com, acme@kernel.org, namhyung@kernel.org, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@kernel.org, irogers@google.com, adrian.hunter@intel.com, kan.liang@linux.intel.com, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v5 1/2] perf/core: Fix small negative period being ignored Message-ID: <20240902092053.GC4723@noisy.programming.kicks-ass.net> References: <20240831074316.2106159-1-luogengkun@huaweicloud.com> <20240831074316.2106159-2-luogengkun@huaweicloud.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240831074316.2106159-2-luogengkun@huaweicloud.com> On Sat, Aug 31, 2024 at 07:43:15AM +0000, Luo Gengkun wrote: > kernel/events/core.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/kernel/events/core.c b/kernel/events/core.c > index c973e3c11e03..a9395bbfd4aa 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -4092,7 +4092,11 @@ static void perf_adjust_period(struct perf_event *event, u64 nsec, u64 count, bo > period = perf_calculate_period(event, nsec, count); > > delta = (s64)(period - hwc->sample_period); > - delta = (delta + 7) / 8; /* low pass filter */ > + if (delta >= 0) > + delta += 7; > + else > + delta -= 7; > + delta /= 8; /* low pass filter */ > > sample_period = hwc->sample_period + delta; > OK, that makes sense, Thanks!