Hpet tsc. I am understanding that it is preferred for virtualization, and for multi-core CPUs due to the way HPET is processed it will require more overhead. To optimize the reliability of the TSC clock, you can configure additional parameters when booting the kernel, for example: To set it as boot parameter use clocksource=hpet On older hardware the TSC was often unstable and was disabled by the kernel. This part will describe implementation of x86 architecture May 5, 2015 · Current clocksource is hpet, which simply does not work with the applications I am trying to run and acpi_pm gives the same errors. 6 seconds, HPET took slightly over 12 seconds, and ACPI Power Management Timer took around 24 The documentation of Red Hat MRG version 2 states that TSC is the preferred clock source due to its much lower overhead, but it uses HPET as a fallback. Dec 1, 2019 · I'm getting "Marking TSC unstable due to clocksource watchdog" after some hours of uptime. TSC + TSC without desync: bcdedit /deletevalue useplatformclock - bcdedit /deletevalue useplatformtick - make sure HPET is enabled in BIOS 2. High Precision Event Timer Driver for Linux ¶ The High Precision Event Timer (HPET) hardware follows a specification by Intel and Microsoft, revision 1. is it right? or nope? my question is that when I should consider to change the clocksource between 'tsc' and 'hpet'? or Do I just use Oct 25, 2011 · Probably solved the issue: by setting the tsc=unstable kernel boot parameter, and re-enabling HPET in the UEFI/BIOS, the Linux kernel decided to use hpet as clocksource since boot time and has been running fine for around a week. However, what was noted by many gamers trying to optimize their systems is that HPET can also cause FPS loss, freezes in games, and higher latency overall. A benchmark in that environment for 10 million event counts found that TSC took about 0. With the advent of multi-core/hyper-threaded CPUs, systems with multiple CPUs, and hibernating operating systems, the TSC cannot be relied on to provide accurate results Wikipedia:Time Stamp Counter May 8, 2012 · Enabling HPET in BIOS is just half way of enabling HPET, it needs to be enabled in OS too, and in a way that it's the only timer used. People are calling out Intel as cheaters when actually the opposite is going on. I was locked at ~30 fps, but the connection between me making an action, and the game server responding Nov 11, 2024 · 今天跟着Intel的开发手册，看看如何随着Intel对TSC不断的修改和增加新特性，让TSC从一个简单的性能计数器发展成当前Linux上x86平台最重要的时钟源之一。 Oct 18, 2014 · Just like you, none of the three clocksources (tsc, hpet nor acpi_pm) solved this issue for me. right? but I think in some workload or some environment, 'hpet' is useful perhaps. exe as administrator and type in: bcdedit /set useplatformclock true bcdedit /set tscsyncpolicy enhanced bcdedit /set 高精度事件计时器 （英語： High Precision Event Timer，缩写 HPET），也称 高精度事件定时器，它是 个人电脑 中使用的一种 硬件 计时器，由 英特尔 （Intel）与 微软 共同开发，并自2005年以来已被纳入 芯片组。 使用不支持硬件HPET的旧款 操作系统 的设备只能使用旧型号计时设备，例如 可编程间隔计时器 XBitLabs - Everything Tech Configuring Additional Boot Parameters for the TSC Clock While there is no single clock which is ideal for all systems, TSC is generally the preferred clock source. Disabling HPET won't help if your TSC is stable. 04% (or ~875KHz -- less than 1 tick of the TSC). 6秒，而HPET花费略微超过12秒，ACPI电源管理计时器花费约24秒。 HPET is the High Precision Event Timer. the lower the timer the smoother the machine becomes. HPET has more overhead plain and simple. Each HPET has one fixed-rate counter (at 10+ MHz, hence “High Precision”) and up to 32 comparators. I just want to know the specifics. Other users may need to enforce Windows to use the HPET to get the high-resolution timer. The documentation of Red Hat MRG version 2 states that TSC is the preferred clock source due to its much lower overhead, but it uses HPET as a fallback. Some Intel processors suffered from decreased performance in games and other benchmarks. Environment Mar 31, 2021 · 本文详细介绍了Linux内核在x86_64架构下如何初始化和使用不同的时钟源，包括TSC（TimeStampCounter）、HPET（HighPrecisionEventTimer）和ACPI PM（PowerManagementTimer）。文章通过源码分析了它们的频率、初始化过程和在系统中的角色，强调了TSC作为最高评级的时钟源。 I verified that the calibration source was the HPET and that it had correctly determined the TSC frequency (2. [4] Nov 24, 2023 · Для отключения HPET и активации таймера TSC мы должны в разделе «Системные устройства» отключить « Высокоточный таймер событий » иногда он подписан как High Precision Even Timer. You can disable bios via GRUB, scewin, mod bios, or like that. Apparently Nehalem introduced better handling of TSC. The hpet_set_mapping function just maps the virtual address spaces for the timer registers: 上記の例では、TSC、HPET、および ACPI_PM クロックソースが利用できます。 現在使用中のクロックソースは、 /sys/devices/system/clocksource/clocksource0/current_clocksource ファイルを読み取ることで検査できます。 Jul 17, 2023 · High Precision Event Timer (HPET) 是一种高精度的硬件计时器，广泛用于计算机系统中以提供更精确的时间和事件管理。HPET 主要用于处理定时任务、系统事件、以及操作系统和应用程序的精确定时需求。以下是 HPET 在 Windows 操作系统发展过程中的时间线概览： 1. However, HPET didn’t become the main timer mainly because of the huge access time. Marking TSC unstable due to check_tsc_sync_source failed Mobo - R4E CPU - i7 3970X Memory - Corsair 32GB kit 2400mhz BIOS - 3301 OS: Fedora 17 Custom water CPU is overclocked to 5. 6秒，而HPET花费略微超过12秒，ACPI电源管理计时器花费约24秒。 Aug 2, 2010 · On processors with invariant TSC support, the OS may use the TSC for wall clock timer services (instead of ACPI or HPET timers). 8k次。本文详细解读了x86_64架构中的各类时钟源，包括RTC（实时时钟）、PIT（可编程间隔定时器）、HPET（高精度事件定时器）、TSC（时间戳计数器），以及ACPI相关的计时器解决方案，帮助理解主板时钟管理的关键技术。 Apr 25, 2024 · 查询相关资料，发现在Linux操作系统上tsc是首选时钟源——因为它的开销低很多，而hpet作为后备时钟源。一个千万次事件计数的基准测试显示，TSC花费约0. js QueryPerformanceCounter for its monotonic clock with fall-backs to HPET or ACPI PM timer in case an invariant TSC is not present and CLOCK_MONOTONIC on Linux. RDTSCP is a serializing May 27, 2024 · linux pit hpet tsc，Linux操作系统中有许多重要的内核参数和相关的机制，其中包括红帽（RedHat）系统中一些关键的特性，如PIT（ProgrammableIntervalTimer）、HPET（HighPrecisionEventTimer）和TSC（TimeStampCounter）等。这些参数和机制在Linux系统中发挥着至关重要的作用，为系统的稳定性和性能提供了强大的支持。首先 May 9, 2022 · 本文探讨了tsc时钟源在Linux系统中出现不稳定的情况，包括查看时钟源无tsc选项、dmesg显示tsc不稳的问题。针对这些问题，提出了通过启动参数`tsc=reliable pmtmr=0x0`来解决，并讨论了为何没有切换到HPET时钟。同时，文章提到了kvm-clock在虚拟机中的缺点，可能导致CPU占用率升高和时钟回跳现象，以及rdtsc The HPET is fully supported in Windows Vista and Windows 2008 (and later versions). 6 seconds, HPET took slightly over 12 seconds, and ACPI Power Management Timer took around 24 seconds. HPET is a chipset device and scales bad when multiple CPUs try to access it simultanously as the access is serialized in hardware. Modifying the kernel as to disable HPET and force an unstable TSC to be accepted causes issues with graphics and overall stability. x86_64 related clock sources This is sixth part of the chapter which describes timers and time management related stuff in the Linux kernel. You got it completely wrong. so i dont really understand the Oct 9, 2021 · 文章浏览阅读4. Jun 4, 2020 · The is_hpet_capable function checks that we didn’t pass hpet=disable to the kernel command line and the hpet_address is received from the ACPI HPET table. Feb 26, 2025 · 如果系统检测发现 tsc 的漂移超过内核设定的阈值，系统会标记 tsc 为不稳定并自动切换到 hpet。 对应的切换日志通过 dmesg -T 命令可以查看出来： tsc: Marking TSC unstable due to clocksource watchdog或者tsc: Marking TSC unstable due to TSCs unsynchronized。 Disabling HPET won't help if your TSC is unstable. Do you have HPET enabled or disabled in your system? 从2010年开始，禁用【高精度计时器HPET】成了Windows性能优化的一种潜在共识。 2005年，由Intel与微软共同研发的一种硬件计时器标准，纳入了PC芯片组的标准范畴。 Aug 24, 2015 · > Why is the TSC preferred to the HPET as a clocksource for the x86 > architecture? Performance. PIT/TSC/HPET 作为系统时钟的硬件时钟源，三者主要提供的精度不同，系统时钟主要更新系统jiffies。 系统时钟由global_clock_event表示，如果使用PIC则global_clock_event指向i8235_clockevent对象；如果使用HPET则指向hpet_clockevent。 Apr 26, 2018 · Anandtech recently released an article that pointed out problems with their CPU reviews due to an enabled High Precision Event Timer in Windows. Image source Youtube 水平及维护精力所限，文中不免存在错误 Timers and time management in the Linux kernel. " How would I enable Invariant TSC or regular TSC for that matter? I'm assuming it is bcdedit /set tscsyncpolicy Enhanced and Jul 28, 2024 · Linux 时钟源之 TSC：软硬件原理、使用场景、已知问题（2024） Published at 2024-07-28 | Last Update 2024-10-10 本文整理了一些 Linux 时钟源 tsc 相关的软硬件知识，在一些故障排查场景可能会用到。 Fig. Obviously TSC and HPET are firmware/hardware level functionality that the kernel is already dealing with. 004082] clocksource: timekeeping watchdog on CPU46: hpet retried 2 times before success Disabling HPET gave my 5600x a massive performance increase in some games. Dec 21, 2023 · 红框里如不是HPET即未启用，正常为TSC无需修改。 查看方法2：右击CMD管理员权限打开，输入bcdedit回车，最后一行如果没显示useplatformclock则未启用HPET Issue Which clock source for e. Sep 9, 2016 · Intel: How to Benchmark Code Execution Times on Intel®IA-32 and IA-64 Instruction Set ArchitecturesIntel: IA-PC HPET SpecificationIntel: Intel® 64 and IA-32 Architectures Software Developer’s Manual Volume 3A: System Programming Guide, Part 1Intel: Intel® 64 and IA-32 Architectures Software Developer’s ManualIntel’s original CPU TSC 高精度事件计时器（英语：High Precision Event Timer，缩写HPET），也称高精度事件定时器，它是个人计算机中使用的一种硬件计时器，由英特尔（Intel）与微软共同开发，并自2005年以来已被纳入PC芯片组。英特尔以前曾有多媒体计时器（Multimedia Timer），因此选择了HPET作为术语，避免与作为软件特性在 May 3, 2018 · The Linux kernel can also use HPET as its clock source. The HPET (High Precision Event Timer) is a timer that is used in most PCs and in some cases, it increases performance since it is a very precise timer. Nov 6, 2019 · TSC + TSC without desync: bcdedit /deletevalue useplatformclock - bcdedit /deletevalue useplatformtick - make sure HPET is enabled in BIOS im also using custom timer resolution from islc of 0. The term "High Precision Event Timer" is then used within the driver manager to describe TSC (Time-Stamp-Counter) or ACPI Power Management Timer (PMTimer) timing subsystems even when the 15 MHz Intel HPET device is not being used. Dec 5, 2012 · Calling up QPC with HPET takes 700ns to read for instance, 10x what the post quotes, while using TSC timer is 20ish ns. 5MHzish, HPET would show 14. I know a lot of people over the years claim that HPET worked the best for them, but I'm suspicious of their declarations. HPET + RTC: bcdedit /set useplatformclock Yes - bcdedit /set useplatformtick Yes - make sure HPET is enabled in BIOS Jan 30, 2014 · The problem is encountered within a multi-clock domain beginning in 2008 R2 when the TSC was re-introduced as the default Clock (as mentioned above) Vs the use of the HPET (or Power Management (ACPI / PMclock)) Clock that prior OS versions used. Why is this issue occurring and what should you do with HPET and your Windows timer Feb 10, 2023 · However, recent intel CPUs include a constant rate TSC which counts the passage of time rather that the number of CPU clocks. Depending on the application requirement, users may need to disable the HPET to decrease the Deferred Procedure Call (DPC) latency. I need TSC to work. Why? Apr 4, 2023 · TSC Clocksource Switching to HPET During High I/O Load This document (000021035) is provided subject to the disclaimer at the end of this document. Reading from the TSC is faster, which provides a significant performance advantage when timestamping hundreds of thousands of messages per second. We take this opportunity to Jul 18, 2017 · Jul 18 16:39:00 Tower kernel: clocksource: 'tsc' cs_now: 58701fecccb cs_last: 586cfe2c152 mask: ffffffffffffffff Jul 18 16:39:01 Tower kernel: clocksource: Switched to clocksource hpet The HPET issue affects older processors or processors unable to use tsc more than modern ones. I forget the exact frequencies, but TSC has always been considered the best timer to use in most setups for gaming. 1Ghz). ``` [1198064. I also compared the HPET vs the TSC measurements: HPET: 2100836143 PIT: 2099960238 A difference of < 0. Jan 4, 2014 · Generally, I recommend not using HPET as a system timer if you have Windows 7 on up and a Core i5/7 (or AMD equivalent) based system. It is also much May 2, 2014 · TSC timers can't be used alone because they don't stay in sync hence why HPET and LAPIC are either used instead of TSC, or are used as well so that the TSC timer's very low latency can be taken advantage of without the issue of them going out of sync. "On Nehalem and later cpus, the rdtscp instruction returns the TSC and an identifier indicating on which cpu you read the TSC. 高精度事件计时器（英语：High Precision Event Timer，缩写HPET），也称高精度事件定时器，它是个人电脑中使用的一种硬件计时器，由英特尔（Intel）与微软共同开发，并自2005年以来已被纳入芯片组。 在上面的示例中，内核使用的是 kvm-clock。这是在启动时选择的，因为它是一个虚拟机。请注意，可用的时钟源取决于构架。 要覆盖默认时钟源，请在内核 GRUB 2 菜单条目的末尾附加 clocksource 指令。使用 grubby 工具进行更改。例如：要强制系统中的默认内核使用 tsc 时钟源，请输入以下命令： Apr 30, 2021 · 文章浏览阅读1. 083468] TSC deadline timer e Feb 18, 2014 · Other Clock Sources While the TSC is generally the preferred clock source, given its accuracy and relatively low overhead, there are other clock sources that can be used: The HPET (High Precision Event Timer) was introduced by Microsoft and Intel around 2005. HPET does however lead to the lowest process and DSC latencies, but the difference of a couple microseconds is literally unnoticeable, and is nowhere near worth the gaming performance hit. System is Threadripper 3960x, Asus TRX40-pro with the latest available bios, 8x8G 3200 sticks. However switching a modern processor to use HPET absolutely cripples the performance on my 10920X specifically with UE4 games. The use of HPET as the primary clocksource has been observed to negatively impact the performance of numerous workloads that rely on accurate Time Stamp Counter (TSC) timing information, such as SAP HANA systems, as referenced on SAP Note 2753418 . TSC + RTC: bcdedit /deletevalue useplatformclock - bcdedit /set useplatformtick Yes 3. 5k次，点赞6次，收藏17次。TSC时钟是一种高精度的硬件时钟,可提供微秒级的时间精度。它利用处理器的时间戳计数器来直接读取时间戳,从而达到高精度。TSC时钟现已在主流的X86和ARM架构处理器中广泛应用。TSC时钟工作原理简单,时钟频率等于处理器时钟频率,每经过一个处理器时钟周期 Jan 1, 1970 · The Time Stamp Counter (TSC), the High Precision Event Timer (HPET), the ACPI Power Management Timer (ACPI_PM), the Programmable Interval Timer (PIT), and the Real Time Clock (RTC). g. TSC is more reliable? basically 'hpet' does consume more cpu time than 'tsc'. But Linux has a special-case performance optimization for time calls. 8k次。本文介绍了如何在Linux系统中查看和设置时钟源，如tsc、hpet和acpi_pm。默认时钟源为tsc，但可以使用echo命令切换到hpet。讨论了Linux为何偏好TSC时钟源，因为其高频率和快速读取，且现代TSC具有constant_tsc和nonstop_tsc特性，不受CPU频率变化影响精度。 The best performance is from TSC+HPET backup, followed by TSC+LAPICS backup, followed by LAPICS only, followed finally by HPET only. May 25, 2025 · For counters; ignoring "emulated with something else", the options in order of best precision are: TSC, HPET, ACPI power management timer For fixed frequency IRQ; ignoring "emulated with something else", the options in order of best precision are: local APIC timer, HPET, PIT, RTC Feb 10, 2021 · 其中CPU中的TSC寄存器是精度最高（与CPU最高主频等同），访问速度最快（只需一条指令，一个时钟周期）的时钟源，因此内核优选TSC作为计时的时钟源。其它的时钟源，如HPET, ACPI-PM，PIT等则作为备选。 但是，TSC不同与HPET等时钟，它的频率不是预知的。 Dec 1, 2022 · For example, TSC timer would show something like 3. 5MHzish etc. I also repeated the same test on a Bhyve VM. Apr 10, 2020 · Ok, do you know why the TSC got increased when Microsoft changed the HPET, isn't the TSC just another timer on the CPU, why would it be affected by the HPET? Unless they're intertwined somehow (which they probably are). May 4, 2015 · 当前的时钟源是hpet，它根本不适用于我试图运行的应用程序，而且acpi_pm也会给出同样的错误。我需要TSC来工作。我已经禁用了intel_pstate并将故障转移设置为acpi_pm。我还有什么办法让TSC再起作用呢？May 4 17:49:18 Ubuntu-1404-trusty-64-minimal kernel: [ 0. 希望するクロックソースは Time Stamp Counter (TSC) ですが、利用できない場合には、HPET (High Precision Event Timer) が 2 番目に適しています。 ただし、すべてのシステムに HPET クロックがあり、一部の HPET クロックは信頼できない場合があります。 The HPET registers allow the kernel to read and write the values of the counters and of the match registers, to program one-shot interrupts, and to enable or disable periodic interrupts on the timers that support them. Now I advice to disable HPET because even if you have it enabled in BIOS, Windows 10 won't use it by default, but it will install the system device driver May 14, 2010 · Generally they're within 1 or 2 seconds of drift each day, which isn't too bad. But we've neglected one clock source: NTP. Since then a lot of misconceptions are going around. " So, if TSC can be used for wallclock, they are guaranteed to be in sync. To try this workaround, run cmd. that means that 'hpet' is not useful as a clocksource. 1GHz, Apr 8, 2018 · 本文分析了Linux系统中的clocksource管理，介绍了kvm-clock、tsc、hpet、acpi_pm和pit等timer的实现与使用。Linux通过rating管理clocksource，kvm-clock在虚拟化中性能最佳。各timer通过不同方式向Guest注入IRQ，确保时间精度。 Jul 28, 2024 · Linux 时钟源之 TSC：软硬件原理、使用场景、已知问题（2024） Published at 2024-07-28 | Last Update 2024-10-10 本文整理了一些 Linux 时钟源 tsc 相关的软硬件知识，在一些故障排查场景可能会用到。 Fig. Some users said its the other way around. 1 would automatically use it and install system device driver for it. Jul 12, 2020 · On Windows, Node. 5 and i can definitely notice every step of granularity. In the previous part we saw clockevents framework and now we will continue to dive into time management related stuff in the Linux kernel. Apr 7, 2025 · Hello everyone who came. HPET was designed by Microsoft and AMD to replace old timers like Time Stamp Counter (TSC) Time Stamp Counter (TSC) and be the main timer for high-precision measurements. Reading from the TSC means reading a register from the processor. Jan 9, 2013 · TSC synchronization [CPU#0 -> CPU#1]: Measured 45807324137 cycles TSC warp between CPUs, turning off TSC clock. By default windows uses combination of TSC+ACPI timers, not 例えば、ハードの実装によるTSCの機能の違いにも依るでしょうし、TSC 自体がそもそもハイパーバイザのエミュレーションによって実装されていることすらもあります。 May 30, 2023 · 文章浏览阅读7. But they have their own oscillator that operates at a much a looser frequency than an HPET or TSC, and they don't have passive counter options like the HPET, TSC, and RTC. TSC reads are much more efficient and do not incur the overhead associated with a ring transition or access to a platform resource. Nov 11, 2020 · 今回は、current clocksourceの設定確認～変更の方法までまとめて説明していきたいと思います。 そもそもclocksourceとは clocksourceとは、ざっくり言うとOSが時刻を取得するためのソースのことを指し、current clocksourceとはその名の通り現在設定されているclocksourceのことを指します。 clocksourceにはXen Mar 4, 2015 · HPET は High-Precision Event Timer の略で、10MHz 以上のクロックをカウントする 32bit または 64bit のカウンターです。 PITを代替する目的で導入されました。 Mar 9, 2024 · I tried using high precision event timer (HPET) as the clocksource for my system to see if it would benefit performance in gaming today, and the system performed normally with clocksource=hpet invoked on the kernel command line, but when playing a game it produced really strange performance. anyway, if you want disable HPET in bios, always make sure deletevalue useplatformtick / useplaftformclock. HPET vs. Apr 1, 2019 · The CPU is new enough to use TSC. Anyway, my question is simple. HPET is a timer placed somewhere on the motherboard. I've recently noticed that the Fast TSC calibration fails only at night when I arrive home after work. An additional concern is that timers based off the TSC (or HPET, if the raw bus clock is exposed) may now be running at different rates, requiring compensation in some way in the hypervisor by virtualizing these timers. TSC access is extremly fast as it is a per CPU register. I already disabled intel_pstate and set failo Aug 30, 2020 · Enable/disable HPET and Dynamic Ticks Some users claim that forcing High Precision Event Timer (HPET) as a main timer and disabling dynamic ticks solve latency issues and audio distortion. The HPET registers allow the kernel to read and write the values of the counters and of the match registers, to program one-shot interrupts, and to enable or disable periodic interrupts on the timers that support them. In these newer systems, Windows uses the newer Invariant TSC, which is a much more reliable and consistent system timer than HPET. (this removes the need for UsePlatformTick and wont be shown in the bootloader or terminal) High Precision Event Timer (HPET) Is a high resolution system timer that uses interrupts in order to maintain a rate of time. In the absence of TSC and HPET, other options include the ACPI Power Management Timer (ACPI_PM), the Programmable Interval Timer (PIT), and the Real Time Clock (RTC). Nov 28, 2023 · Red Hat MRG第二版的文档指，TSC是首选时钟源——因为它的开销低很多，而HPET作为后备时钟源。 一个千万次事件计数的基准测试显示，TSC花费约0. Scaling up crystal frequency for different components of a computer. Image source Youtube 水平及维护精力所限，文中不免存在错误 Nov 6, 2019 · 1. Part 6. Reading from the HPET clock means reading a memory area. (im post guide on this forum how find hidden settings in bios file and use grub to change settings) I could use hpet or unstable for the clocksource configuration Another thought it whether it's worth trying to use a LXC as a lightweight desktop with iGPU instead - if that's possible (simple non-graphical LXCs work well). Aug 2, 2015 · When HPET (High Precision Event Timer) was enabled in BIOS, Windows 8. This is my system: motherboard:b550 gigabyte gaming x v2 [last bios] cpu: ryzen 7 5800x3d [last driver] gpu:ASUS DUAL RTX 3060 Ti OC V2 LHR [last driver] ram:team group t-create 3600 cl14 power suply:Cougar GEX750 So i want to ask you about some game perfomance and pc PSA: Disable HPET (High Precision Event Timer) for smoother gameplay with more FPS. Its precision is approximately 100 ns, so it is less accurate than the TSC, which can provide sub-nanosecond accuracy. Apr 4, 2023 · There have been several reports of the TSC clocksource switching to HPET under high load. Jul 28, 2023 · HPET is disabled by def in windows, but TSC can use that for correct timer. . Even on a UP system the access overhead is somewhere in the range of factor 100. Nov 8, 2017 · I have an Athlon II x4 640 which I believe it is able to use invariant TSC since on cpuworld it says "TSC rate is ensured to be invariant across all states. duph tmfg pye hqaec cnvb uuop vlfous rnx annhv honf