From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 D878910F2 for ; Thu, 21 May 2026 21:07:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779397642; cv=none; b=GKAcIkVcmswVdVJkmhbxN4+UiPVjwO5p7se+SS8slHSJGSj3C+T8N6LWctaKYXtYvp3TeAATqohJOdNIGihdt85AJDMb01CtL+3+sxJ0j3HH45+ooagjpj6HMjF7ztCaQ1XwKwSSSOkfi/uWtGu8mgfofJYru/4CQT4rOIiXpLA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779397642; c=relaxed/simple; bh=6PAI20ufAuPTfUr80/ZTXnoEjqWetAS8m5YxvhyjMkk=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=cwiZwZLSK6qaAxXk670eJeVoBl8/bn+O7zUuQiuJtEFj9hTK7q3iAR1EfqnxAOp25G16rxRrUiURsSZXXINWc91+hpkzFWQUEd8j1nh4d00QFAHdvOBDktU0w4yv1mhr7ti2Oz7D8A+j3QUhc1vcCBd0eDYOwhoFhp925rvfWMA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=iEpKl2lg; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="iEpKl2lg" Received: by smtp.kernel.org (Postfix) with UTF8SMTPSA id A705C1F000E9; Thu, 21 May 2026 21:07:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779397641; bh=q+vxGGIzAWeuZzRBggMNRZl3uqOCd/6Wy+o/DIT0mNo=; h=From:To:Cc:Subject:In-Reply-To:References:Date; b=iEpKl2lgA5w3BGtI0kHJ4jKGgEZKiUHbWyeyHUEv6F5WU4YO95VBikCEKviwNBHn3 qRzRFHA020Qqqw3PfRa2SVO1jOOGDiMLX7+umh0Qm6lYhNoHVhB/zN83oMGp19pJ30 by1Q6fGZiCUUOm6iBEf8Bsg5Gz6kG33cUnNaviaexU4j/E5tUve2X2iXX0orafVyT7 K+r+Lx+7abA3rmRc0s3AP1IYaqFznk/MS2EGxceNdd7B6Y50MMvRIodFiG6GwZzZHl Xw1VXwShBQ80eqWWjqGj05eUyl5EVcClQaAVTYj4fc8V4JPt38z1+QzZDWY69VQl1l BxdknebIc7vzw== From: Thomas Gleixner To: Shrikanth Hegde , LKML Cc: x86@kernel.org, Michael Kelley , Dmitry Ilvokhin , Radu Rendec , Jan Kiszka , Kieran Bingham , Florian Fainelli , Marc Zyngier Subject: Re: [patch V6 00/16] Improve /proc/interrupts further In-Reply-To: References: <20260517194421.705253664@kernel.org> <87wlwyw188.ffs@tglx> <0ef61565-dc6c-4281-ad85-ddfff87078a7@linux.ibm.com> <87jysxw65f.ffs@tglx> Date: Thu, 21 May 2026 23:07:17 +0200 Message-ID: <87fr3kv5dm.ffs@tglx> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain On Thu, May 21 2026 at 20:18, Shrikanth Hegde wrote: > On 5/21/26 1:23 PM, Thomas Gleixner wrote: >> It doesn't add up completely, but the trend is there. And you can trick >> perf to reveal the startup/teardown overhead it by comparing: >> >> perf stat -r 1000 head -q -c -0 /proc/interrupts >/dev/null >> perf stat -r 1000 head -q -c 0 /proc/interrupts >/dev/null >> > Tried it, but doesn't affect much. Weird. On a v6 patched kernel: $ perf stat -r 1000 head -q -c -0 /proc/interrupts >/dev/null 0.00130456 +- 0.00000306 seconds time elapsed ( +- 0.23% ) $ perf stat -r 1000 head -q -c 0 /proc/interrupts >/dev/null 0.00108667 +- 0.00000367 seconds time elapsed ( +- 0.34% ) The -c -0 one reads the full output while the -c 0 one just opens the file and closes it again, which means the actual read takes ~0.3ms while the startup/teardown takes 1ms. >> printf("%lu %lu %5.3f\n", tsum / LOOPS, rs / LOOPS, (std / mean) * 100.0); >> return 0; >> } > > This shows real benefits indeed. > > base v6 v6+ppc_hack > 101us 65us 57us > > So doing a proper powerpc fix indeed would make sense. > I think it is going to be similar. Let me go and read your > series again. Have fun! > For the genirq bits of the series, consider the tag if applicable > > Tested-by: Shrikanth Hegde Thank you! tglx