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From: Isaac Boukris <iboukris@gmail.com>
To: Stephen Hemminger <stephen@networkplumber.org>
Cc: users@dpdk.org
Subject: Re: Accuracy of rte_get_tsc_hz() compared to linux
Date: Thu, 19 Sep 2024 21:33:28 +0300	[thread overview]
Message-ID: <CAC-fF8R-xv9o5oOE7gOegW7nKgDLB3DJN06zWFUydLtoF1zvHg@mail.gmail.com> (raw)
In-Reply-To: <CAC-fF8T_T1W2zsWH3J8VQiRJDfh3LWNx8z6825U8ed5rNbBCoQ@mail.gmail.com>

Looking some more at the kernel code (tsc.c), it appears that it would
only trust the arch frequency if the cpu 'tsc_known_freq' flag is set
(which none of the machines I have access to has, although for some
the dpdk's get_tsc_freq_arch() does return a value), otherwise it
would calibrate it (hence the "Refined" in dmesg). Perhaps we should
do the same.

        /*
         * When TSC frequency is known (retrieved via MSR or CPUID), we skip
         * the refined calibration and directly register it as a clocksource.
         */
        if (boot_cpu_has(X86_FEATURE_TSC_KNOWN_FREQ)) {

  reply	other threads:[~2024-09-19 18:33 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-09-18 22:04 Isaac Boukris
2024-09-18 23:27 ` Stephen Hemminger
2024-09-19  9:37   ` Isaac Boukris
2024-09-19 12:26   ` Isaac Boukris
2024-09-19 13:04     ` Isaac Boukris
2024-09-19 18:33       ` Isaac Boukris [this message]
2024-09-19 21:53 ` Stephen Hemminger
2024-09-19 22:02 ` Stephen Hemminger
2024-09-19 22:21 ` Stephen Hemminger

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