From nobody Mon Feb 9 03:13:24 2026 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 06808312831; Thu, 22 Jan 2026 10:15:40 +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=1769076942; cv=none; b=cWS+znIwot22V6HvL92TR8T7r6/omRLXpb15kiyf+03uMaCarzrEKWR0l1tBgc7aaBsUN6zIwwsHeMAlc3kfpqq15Xoa0yhSlhm7o6al/m9EYQnQZtESnfThn92nEFHRJJ6SyM8kMR6ccUDSP8bsrZBTWrpuhdMNZm6CcNs3618= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769076942; c=relaxed/simple; bh=2FdVrCa5m4uBNPeKFRKrFIHKsRUAn8z/QfUOW+3Di0o=; h=Date:From:To:Subject:Cc:In-Reply-To:References:MIME-Version: Message-ID:Content-Type; b=KqvfgNfBP7E9B9e3p3s5DyTfOjNksE39cktTSqmknGnSe8uMyHRLJK9kzxrj1Yu2hS0EZBZjdxj5SUYh1Fdxu0ErFlONuyuWyHUtbBCG4W+9sKh8yz0Cj3bYwlNmgE5MxEBUSqsDD4mS1Y9cnemWAGE3QonHmN9Y0ndebTVPKGM= 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=sQRN2OKp; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=U4B2FSgk; 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="sQRN2OKp"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="U4B2FSgk" Date: Thu, 22 Jan 2026 10:15:37 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1769076938; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=4d/Gg95IeMFzHJeR8S3kTzTS+TuAQoAIEhR9rwjrvNk=; b=sQRN2OKpcuZT6aHbZQcloHn1Wt3FhTN/B9QbKfGSfkbqL2T/0L+ahrj6TKoi3t/3Y8iTjW hNRzrDTnZQL0nAkFNoWTw7WswZUQsOmpRBd+aSBUVGz60l2JyJ9nLJG2Pb7BL1LaicE8tl iETdpAbkLAQhVQ3INMrEMxKt3eHhWkshLoP4R6F9S2X0iGJv/+3T7ha818o1bEYhUi++R3 S7irSdN0+ffEw6ryQNxzN5J8jAMmhH8rw/mv2hY9ThUb0dlsadnG+UWBuvMALubTJ/DgA2 pVBSMByJ53b7zuIKKhMht3o8ChAdGydlVXchC32M6FRQLjIazs5aOhYQRbrzZw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1769076938; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=4d/Gg95IeMFzHJeR8S3kTzTS+TuAQoAIEhR9rwjrvNk=; b=U4B2FSgkfHeFVbyKRnNV72vhIes4gyWJjmlZhx49AXmS/7ubKhT5EGjufXbGVjDY3AwlFt EBmK9PoAE4ZUGyCw== From: "tip-bot2 for Peter Zijlstra" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] rseq: Lower default slice extension Cc: "Peter Zijlstra (Intel)" , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20260121143208.073200729@infradead.org> References: <20260121143208.073200729@infradead.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <176907693734.510.9935582863534596484.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Precedence: bulk Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable The following commit has been merged into the sched/core branch of tip: Commit-ID: 21c0e92d0681fbd10ac024311bd09bca439e0bb1 Gitweb: https://git.kernel.org/tip/21c0e92d0681fbd10ac024311bd09bca4= 39e0bb1 Author: Peter Zijlstra AuthorDate: Wed, 21 Jan 2026 14:25:04 +01:00 Committer: Peter Zijlstra CommitterDate: Thu, 22 Jan 2026 11:11:20 +01:00 rseq: Lower default slice extension Change the minimum slice extension to 5 usec. Since slice_test selftest reaches a staggering ~350 nsec extension: Task: slice_test Mean: 350.266 ns Latency (us) | Count ------------------------------ EXPIRED | 238 0 us | 143189 1 us | 167 2 us | 26 3 us | 11 4 us | 28 5 us | 31 6 us | 22 7 us | 23 8 us | 32 9 us | 16 10 us | 35 Lower the minimal (and default) value to 5 usecs -- which is still massive. Signed-off-by: Peter Zijlstra (Intel) Link: https://patch.msgid.link/20260121143208.073200729@infradead.org --- Documentation/userspace-api/rseq.rst | 2 +- kernel/rseq.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/Documentation/userspace-api/rseq.rst b/Documentation/userspace= -api/rseq.rst index 29af6c3..468f6bb 100644 --- a/Documentation/userspace-api/rseq.rst +++ b/Documentation/userspace-api/rseq.rst @@ -79,7 +79,7 @@ slice extension by setting rseq::slice_ctrl::request to 1= . If the thread is interrupted and the interrupt results in a reschedule request in the kernel, then the kernel can grant a time slice extension and return to userspace instead of scheduling out. The length of the extension is -determined by debugfs:rseq/slice_ext_nsec. The default value is 10 usec; w= hich +determined by debugfs:rseq/slice_ext_nsec. The default value is 5 usec; wh= ich is the minimum value. It can be incremented to 50 usecs, however doing so can/will affect the minimum scheduling latency. =20 diff --git a/kernel/rseq.c b/kernel/rseq.c index e423a9b..b0973d1 100644 --- a/kernel/rseq.c +++ b/kernel/rseq.c @@ -517,7 +517,7 @@ struct slice_timer { void *cookie; }; =20 -static const unsigned int rseq_slice_ext_nsecs_min =3D 10 * NSEC_PER_USEC; +static const unsigned int rseq_slice_ext_nsecs_min =3D 5 * NSEC_PER_USEC; static const unsigned int rseq_slice_ext_nsecs_max =3D 50 * NSEC_PER_USEC; unsigned int rseq_slice_ext_nsecs __read_mostly =3D rseq_slice_ext_nsecs_m= in; static DEFINE_PER_CPU(struct slice_timer, slice_timer);