From nobody Fri Oct 3 08:49:05 2025 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 2D23F1B3935; Wed, 3 Sep 2025 09:58:57 +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=1756893540; cv=none; b=a6O2oWCGLYzKI4MKCxRJ5xkRTtffCULvNGxY1PBzFS/aQyJy04mO3ytMi+ZDRJoh7ieEcoi3eGMHTCwIv9/xTDpHAyNSKL1dsPlRe9NNaD43SILrfTlrK7WQjfGJa7nSPKIQa40ZbXh3XCTtrQMQLO+gAlokcVddlWqmGw5u2uM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756893540; c=relaxed/simple; bh=3UiHMYeM4GHtOQtohxHdrM63uaJ52zzDf0Ia/szXyvE=; h=Date:From:To:Subject:Cc:In-Reply-To:References:MIME-Version: Message-ID:Content-Type; b=iQ8GfBUAfW5sanO3Jkkvbv+YqHTDyQyGChlBCfCSx/CRamBcz9JDKQ62SkaiyKGsCzWia9ik+gdtpL/4mEi7evuO1bthITAwjZBQO2ISVE4q9sG0vRWSGvmxOCFpx1Cu541TNfYg/FRh9DiwXUwDRDKgHnaS5ITl4vMMsz36N0Y= 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=wqrhYnMW; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=hM7Zv5F5; 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="wqrhYnMW"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="hM7Zv5F5" Date: Wed, 03 Sep 2025 09:58:53 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1756893534; 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=YMY5Rw67Zd5ivqpebc2I+pt11+SaGI/36GCSjD2kg3s=; b=wqrhYnMWSTn2UFyb8ex5iqCoh4YYel4wCa+EoVRgWD2S3Ar3fBbZAh1ko8+F7iB76dJcuQ gt4zNJDWcioR7v6w7u3w0ulM1W0tZEgKQ4AQK/O4olljmnswEmuvGWxPsOcVhfTxhzV1Hs RevF8PPONdKyGlkHeK/h0Xs6vpcT8H61qj9DxHqWSFyZlXy4NZi2vEMcSI7qg/DiY+SFyf 08/QGrqXrCYZkeDENwwJ8UIwh0iWeTL7ELR9zZioYRMxVAfeufvQOtM9yHSAxuB1y8z/ko 4WY8eENo6dq3clSGvsQLCCW55h+xZucTwC4CATUVpIcxpLp9EQjHLzDwX5SNdA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1756893534; 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=YMY5Rw67Zd5ivqpebc2I+pt11+SaGI/36GCSjD2kg3s=; b=hM7Zv5F5+KlCE5hu0ud4zVwbcvacr58qNTy1gvlyXkfcp3RiWIGJcdk+dFJfl6cpNop54Q VMYbD4vkyIKi6NCQ== From: tip-bot2 for Thomas =?utf-8?q?Wei=C3=9Fschuh?= Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: timers/urgent] vdso/vsyscall: Avoid slow division loop in auxiliary clock update Cc: Miroslav Lichvar , thomas.weissschuh@linutronix.de, Thomas Gleixner , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20250825-vdso-auxclock-division-v1-1-a1d32a16a313@linutronix.de> References: <20250825-vdso-auxclock-division-v1-1-a1d32a16a313@linutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <175689353303.1920.4835241898909824126.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 timers/urgent branch of tip: Commit-ID: 762af5a2aa0ad18da1316666dae30d369268d44c Gitweb: https://git.kernel.org/tip/762af5a2aa0ad18da1316666dae30d369= 268d44c Author: Thomas Wei=C3=9Fschuh AuthorDate: Mon, 25 Aug 2025 15:26:35 +02:00 Committer: Thomas Gleixner CommitterDate: Wed, 03 Sep 2025 11:55:11 +02:00 vdso/vsyscall: Avoid slow division loop in auxiliary clock update The call to __iter_div_u64_rem() in vdso_time_update_aux() is a wrapper around subtraction. It cannot be used to divide large numbers, as that introduces long, computationally expensive delays. A regular u64 division is also not possible in the timekeeper update path as it can be too slow. Instead of splitting the ktime_t offset into into second and subsecond components during the timekeeper update fast-path, do it together with the adjustment of tk->offs_aux in the slow-path. Equivalent to the handling of offs_boot and monotonic_to_boot. Reuse the storage of monotonic_to_boot for the new field, as it is not used by auxiliary timekeepers. Fixes: 380b84e168e5 ("vdso/vsyscall: Update auxiliary clock data in the dat= apage") Reported-by: Miroslav Lichvar Signed-off-by: Thomas Wei=C3=9Fschuh Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/all/20250825-vdso-auxclock-division-v1-1-a1d3= 2a16a313@linutronix.de Closes: https://lore.kernel.org/lkml/aKwsNNWsHJg8IKzj@localhost/ --- include/linux/timekeeper_internal.h | 9 ++++++++- kernel/time/timekeeping.c | 10 ++++++++-- kernel/time/vsyscall.c | 4 ++-- 3 files changed, 18 insertions(+), 5 deletions(-) diff --git a/include/linux/timekeeper_internal.h b/include/linux/timekeeper= _internal.h index c27aac6..b8ae89e 100644 --- a/include/linux/timekeeper_internal.h +++ b/include/linux/timekeeper_internal.h @@ -76,6 +76,7 @@ struct tk_read_base { * @cs_was_changed_seq: The sequence number of clocksource change events * @clock_valid: Indicator for valid clock * @monotonic_to_boot: CLOCK_MONOTONIC to CLOCK_BOOTTIME offset + * @monotonic_to_aux: CLOCK_MONOTONIC to CLOCK_AUX offset * @cycle_interval: Number of clock cycles in one NTP interval * @xtime_interval: Number of clock shifted nano seconds in one NTP * interval. @@ -117,6 +118,9 @@ struct tk_read_base { * @offs_aux is used by the auxiliary timekeepers which do not utilize any * of the regular timekeeper offset fields. * + * @monotonic_to_aux is a timespec64 representation of @offs_aux to + * accelerate the VDSO update for CLOCK_AUX. + * * The cacheline ordering of the structure is optimized for in kernel usag= e of * the ktime_get() and ktime_get_ts64() family of time accessors. Struct * timekeeper is prepended in the core timekeeping code with a sequence co= unt, @@ -159,7 +163,10 @@ struct timekeeper { u8 cs_was_changed_seq; u8 clock_valid; =20 - struct timespec64 monotonic_to_boot; + union { + struct timespec64 monotonic_to_boot; + struct timespec64 monotonic_to_aux; + }; =20 u64 cycle_interval; u64 xtime_interval; diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 059fa8b..b6974fc 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -83,6 +83,12 @@ static inline bool tk_is_aux(const struct timekeeper *tk) } #endif =20 +static inline void tk_update_aux_offs(struct timekeeper *tk, ktime_t offs) +{ + tk->offs_aux =3D offs; + tk->monotonic_to_aux =3D ktime_to_timespec64(offs); +} + /* flag for if timekeeping is suspended */ int __read_mostly timekeeping_suspended; =20 @@ -1506,7 +1512,7 @@ static int __timekeeping_inject_offset(struct tk_data= *tkd, const struct timespe timekeeping_restore_shadow(tkd); return -EINVAL; } - tks->offs_aux =3D offs; + tk_update_aux_offs(tks, offs); } =20 timekeeping_update_from_shadow(tkd, TK_UPDATE_ALL); @@ -2937,7 +2943,7 @@ static int aux_clock_set(const clockid_t id, const st= ruct timespec64 *tnew) * xtime ("realtime") is not applicable for auxiliary clocks and * kept in sync with "monotonic". */ - aux_tks->offs_aux =3D ktime_sub(timespec64_to_ktime(*tnew), tnow); + tk_update_aux_offs(aux_tks, ktime_sub(timespec64_to_ktime(*tnew), tnow)); =20 timekeeping_update_from_shadow(aux_tkd, TK_UPDATE_ALL); return 0; diff --git a/kernel/time/vsyscall.c b/kernel/time/vsyscall.c index 8ba8b0d..aa59919 100644 --- a/kernel/time/vsyscall.c +++ b/kernel/time/vsyscall.c @@ -159,10 +159,10 @@ void vdso_time_update_aux(struct timekeeper *tk) if (clock_mode !=3D VDSO_CLOCKMODE_NONE) { fill_clock_configuration(vc, &tk->tkr_mono); =20 - vdso_ts->sec =3D tk->xtime_sec; + vdso_ts->sec =3D tk->xtime_sec + tk->monotonic_to_aux.tv_sec; =20 nsec =3D tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift; - nsec +=3D tk->offs_aux; + nsec +=3D tk->monotonic_to_aux.tv_nsec; vdso_ts->sec +=3D __iter_div_u64_rem(nsec, NSEC_PER_SEC, &nsec); nsec =3D nsec << tk->tkr_mono.shift; vdso_ts->nsec =3D nsec;