From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 C7FB0329F2F for ; Wed, 10 Sep 2025 14:54:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757516059; cv=none; b=pX08gCAIFzJHtRr0SQzCQqgVERsFkUFkCx1Mle1dEpIMQfjfRhr5YeJrtBH7A2TEuPE7/z8TaP1rGMdW2Xuw3s01TjwbBXXJ5aVGC0fhAbjqACXVR/ccYKAEj4xYwul0zh1pxD9DYoY9lhDB+GHAiEdYTc3xZ36YEBTBq5Fe/Hk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757516059; c=relaxed/simple; bh=XSaX1sxYtqPtQQ8fXDVHqx9RopzIBxiTdAA+e8cMZOU=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=uT6/6XrpdyqtR0ULEb239JofaI3ZHBz9uQinyfk9liVjHZEH2FEsV/HXQzKpmnMhlc/rKQowK8Gw89LOdSy/hpei64B1bPzvP/A0RNYBTrRh07fJmgFFIi09in/5syAn7b35CQmyGP2AsLrVxoxg/7k/vE9MOHb77dZkTQ/xNaE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=HgBKUW2T; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=cv4kftta; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="HgBKUW2T"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="cv4kftta" From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1757516053; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=hgwqXmToXPpmi6iMjwkVoSVLN5sKUJ4q4e/5ofe+WSU=; b=HgBKUW2TGWPSai701tuK9bDxD3f1J3vPUxz+eojSMo1ACqEwt7hU+bEZdV7EhAtqTceSiA Hl955WjKPiGSZNM1+FaF9oMGnzsqIULWTb62zYxET0hVMiqNK9JqnbnSRodb3FxqgPgW8q gruOpIbB+j9C46JwqZzFviY9Qe0WfraTmgxpWVJv4j4tIS7WtY/wibgVcQve1IfCX3faZB KOfjsC5G3iMKBX80rt72FObNsJ448yUUIIXPwAbr6hCcT/HcHnxtxj9dohrMAIT7R5Ze+u GbhzCZoHoF20NOe/UHMi1BsGo1jBDR+bQH9hvLxrgWn4qb4J/I7Pqfs8rKOLow== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1757516053; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=hgwqXmToXPpmi6iMjwkVoSVLN5sKUJ4q4e/5ofe+WSU=; b=cv4kfttatviow1VMz62/65CHr5JnYAgdf0asArhaVo7ut6/5UKOWUH5U0i9D0VeZVXN/wA F86wiEMJmanviNCw== To: Jens Axboe , LKML Cc: Michael Jeanson , Mathieu Desnoyers , Peter Zijlstra , "Paul E. McKenney" , Boqun Feng , Paolo Bonzini , Sean Christopherson , Wei Liu , Dexuan Cui , x86@kernel.org, Arnd Bergmann , Heiko Carstens , Christian Borntraeger , Sven Schnelle , Huacai Chen , Paul Walmsley , Palmer Dabbelt Subject: Re: [patch V4 00/36] rseq: Optimize exit to user space In-Reply-To: <4029c2d2-7a0c-4531-aa1e-b35be9098bb1@kernel.dk> References: <20250908212737.353775467@linutronix.de> <4029c2d2-7a0c-4531-aa1e-b35be9098bb1@kernel.dk> Date: Wed, 10 Sep 2025 16:54:12 +0200 Message-ID: <87bjnitl2j.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 Wed, Sep 10 2025 at 07:55, Jens Axboe wrote: > On 9/8/25 3:31 PM, Thomas Gleixner wrote: >> For your convenience all of it is also available as a conglomerate from >> git: >> >> git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git rseq/perf > > I used this branch for some quick testing. Since I last looked at the > rseq performance overhead, glibc must have improved a few things. FWIW, > box is running libc 2.41 at the moment. Test box is on debian unstable, > so gets frequent updates. In any case, for one of my usual kernel > overhead runs of checking running a basic IOPS based test, I see the > following on the stock (-rc5 + 6.18 targeted changes) kernel running > that test: > > + 0.89% io_uring [kernel.kallsyms] [k] __get_user_8 > + 0.58% io_uring [kernel.kallsyms] [k] __put_user_8 > + 1.13% io_uring [kernel.kallsyms] [k] __rseq_handle_notify_resume > > which is about 2.6% of purely rseq related overhead. Pulling in the > above branch and running the exact same test, all of the above are gone > and perusing the profile has nothing jump out at me in terms of shifting > those cycles to other bookkeeping. > > So yes, this work does make a very noticeable difference! I would have been really surprised if not :) Thanks a lot for testing! tglx