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 64C12330B11 for ; Fri, 19 Jun 2026 07:35:55 +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=1781854557; cv=none; b=PQYEmNBWkINrPEhNXiwTjlYkjVIbGMNZnWCGDcTrg2f/wLT00Fqbp48TIhKNmBGqgfY7Tb1FWB1PpRaqVqKfkk2lnbUWXHAd/5FbJ1XRNoXYOG8grzUbhZV+3+ejBGp6v8WDh5K0w8XZlsQrMqNcI14Px3UdiU+wOPg2qGb/DhQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781854557; c=relaxed/simple; bh=99x9i+bAQDHaRajcHLB21xPdD4R3KWswo4CNflwTaxA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=W3v1J3o1V3BTY3eFf4QHaTDnhkBQf78SYShRA+3KLXm1K+61QfQe6bj4cDHpRF0kR5+DzrG0Qy4kLFJ53cyrB6f1a/VhSKGkTLiEmdPT+lVOD5P0kk7hcgGgjRnfiMR1UfGD6XJqV85HY/yC3q6luis6RtNSoj3DTiGVmjzvl1w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=pass smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=f+pXe0C9; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=pass 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="f+pXe0C9" 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=99x9i+bAQDHaRajcHLB21xPdD4R3KWswo4CNflwTaxA=; b=f+pXe0C9skfVcESrH/N7ZQ0T2w cmnUsNMt3riKFyqKDZQx7B4Wo9MYRNT5B4zr5Z/mcqCU+5e8+JrQbWAMiKyJI4GV2+gszLGuNIkqO pQFOlTGv+kaHrqXMiEhy8KCub9ZjDo5vfAHzr5xXFsi29WSgNaDagBuOA4SGwHIDN3KyyBV1oJYip gBaOAdXTjA30kQsTii8pr14oIl4LNQzKF3MZcH8W7/OeyyzOAzPGQWQ8M2qeSJ3Cao7V09Udq2F/o 1dttN8/G1V9e74Kgtg2DdhWWP0Q+qbh8DBDNEQM7OK2qiG/zCtvLBVNFVpl7ScpCT6xKfmhDW7Idm S3P2H8QQ==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.99.2 #2 (Red Hat Linux)) id 1waTlO-0000000EFQn-3e0w; Fri, 19 Jun 2026 07:35:43 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 3175D300578; Fri, 19 Jun 2026 09:35:41 +0200 (CEST) Date: Fri, 19 Jun 2026 09:35:41 +0200 From: Peter Zijlstra To: "H. Peter Anvin" Cc: Linus Torvalds , tglx@kernel.org, mingo@redhat.com, bp@alien8.de, Nathan Chancellor , Calvin Owens , Dave Hansen , x86-ML , LKML Subject: Re: 8aeb879baf12 - significant system call latency regression, bisected Message-ID: <20260619073541.GR49951@noisy.programming.kicks-ass.net> References: <20260616082814.GQ48970@noisy.programming.kicks-ass.net> <20260617123718.GM49951@noisy.programming.kicks-ass.net> <9ae04c80-d1e2-44f0-bca2-d0889c61b45f@zytor.com> <13791ee3-f699-444a-ae1b-a18c2c281f67@zytor.com> <0b6889d3-173b-4143-a4a2-76630482959a@zytor.com> Precedence: bulk X-Mailing-List: linux-kernel@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: <0b6889d3-173b-4143-a4a2-76630482959a@zytor.com> On Thu, Jun 18, 2026 at 09:32:29PM -0700, H. Peter Anvin wrote: > improvements (I spotted a couple of possibilities already, like it calling > instrumentation_begin..._end twice.) Unless you have DEBUG_ENTRY=y, that is a no-op. Release builds should not have DEBUG_ENTRY methinks.