From mboxrd@z Thu Jan 1 00:00:00 1970
Return-Path: <dev-bounces@dpdk.org>
Received: from dpdk.org (dpdk.org [92.243.14.124])
by inbox.dpdk.org (Postfix) with ESMTP id 9DFC4A00BE;
Mon, 27 Apr 2020 21:34:05 +0200 (CEST)
Received: from [92.243.14.124] (localhost [127.0.0.1])
by dpdk.org (Postfix) with ESMTP id AFF811D424;
Mon, 27 Apr 2020 21:34:04 +0200 (CEST)
Received: from mail-lj1-f196.google.com (mail-lj1-f196.google.com
[209.85.208.196]) by dpdk.org (Postfix) with ESMTP id 1B2341D423
for <dev@dpdk.org>; Mon, 27 Apr 2020 21:34:03 +0200 (CEST)
Received: by mail-lj1-f196.google.com with SMTP id g4so18916630ljl.2
for <dev@dpdk.org>; Mon, 27 Apr 2020 12:34:03 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025;
h=date:from:to:cc:subject:message-id:in-reply-to:references
:mime-version:content-transfer-encoding;
bh=u+csVrEg2NCC8vMPWO2AEWRm3gS7raepsu5+whvrB6E=;
b=LmxEm7wIXMbtgEwMdBukLWtkpFDMiY9dmbC2KAUl6nO+2rd3zFB+h/H8vs0GIy9vie
cPkUWS/3ggAyIOTBM6TP0arqiyXsQmxWd8jzKrYyTg4+YTklRmRg/vr2EgOCIYzzCi/l
lkrEx4zEzMQVAeAUQ2FbGCFQMlhmkM1PrFvxPX/L6KriehGVdGwAxrGd++7/96ZNzNku
iwsluTMs+SZXh2ctDpbZQlNpPsxfTCaPZWklOGssyKYVZCkbblFHY/dy/bUcv4XSyUJZ
UyEObGMgn9Wkt/zZqGF5amTSTXPftF7ecvcigaEIJifZ4MgXvZgnS2QpNzYgR7pmISBN
bBAw==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
d=1e100.net; s=20161025;
h=x-gm-message-state:date:from:to:cc:subject:message-id:in-reply-to
:references:mime-version:content-transfer-encoding;
bh=u+csVrEg2NCC8vMPWO2AEWRm3gS7raepsu5+whvrB6E=;
b=QNUJdn5tmFcukViN+EO/h+xS37RmLIL3LD12ZCU42+77lUfoTYouR3aGZyVUF0ui4n
MgQOfwQgZbf4eEUnL8Bc/2prRfCh00RzS4TL9cJgDjMLmellvmeeGZYd4MUaNSoUZbZ3
zvASZ4pJN/JL/7vN+zgw7Rez1cdxAUJV9R7R++d5PTeGiz2d5Bj8L/eyuxWw5Uk6NGFO
P3tqHBsdGDSEdG/0xajRrxCpio11weZUHe3D38DLk09KMt1AqBo2d/8QidRs/DX9oOzn
vyBSh7rPblzHlfI5RMVo7bO+MgMZdWIO4uBRzhLC2JkD7Xi3Rwd2FIhQR3z2Jvp7oH++
WA8Q==
X-Gm-Message-State: AGi0Pua2lgOMI52JKMUdtZmk2dvFGlTDTy03sAJ9pQ2ClqjFHQueOwMZ
mdTT8HqSU9gmiTO6Uz7GbRI=
X-Google-Smtp-Source: APiQypI/OceMkfUcZENN6Tt48wBT7SKYR1NCS4ZNEoq6NeUTWggQVfWNs82TrRsxM3BMN4gS0ZxbJQ==
X-Received: by 2002:a2e:b6cf:: with SMTP id m15mr14700891ljo.168.1588016042498;
Mon, 27 Apr 2020 12:34:02 -0700 (PDT)
Received: from Sovereign (broadband-37-110-65-23.ip.moscow.rt.ru.
[37.110.65.23])
by smtp.gmail.com with ESMTPSA id p23sm11633803lfc.95.2020.04.27.12.34.01
(version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256);
Mon, 27 Apr 2020 12:34:01 -0700 (PDT)
Date: Mon, 27 Apr 2020 22:34:00 +0300
From: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>
To: Fady Bader <fady@mellanox.com>
Cc: dev@dpdk.org, thomas@monjalon.net, talshn@mellanox.com,
dmitry.koziuk@gmail.com, harini.ramakrishnan@microsoft.com,
ocardona@microsoft.com, anand.rawat@intel.com, ranjit.menon@intel.com
Message-ID: <20200427223400.70f5bbe7@Sovereign>
In-Reply-To: <20200427122047.16780-3-fady@mellanox.com>
References: <20200427122047.16780-1-fady@mellanox.com>
<20200427122047.16780-3-fady@mellanox.com>
X-Mailer: Claws Mail 3.17.5 (GTK+ 2.24.32; x86_64-pc-linux-gnu)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Subject: Re: [dpdk-dev] [PATCH v2 2/2] timer: support EAL functions on
Windows
X-BeenThere: dev@dpdk.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: DPDK patches and discussions <dev.dpdk.org>
List-Unsubscribe: <https://mails.dpdk.org/options/dev>,
<mailto:dev-request@dpdk.org?subject=unsubscribe>
List-Archive: <http://mails.dpdk.org/archives/dev/>
List-Post: <mailto:dev@dpdk.org>
List-Help: <mailto:dev-request@dpdk.org?subject=help>
List-Subscribe: <https://mails.dpdk.org/listinfo/dev>,
<mailto:dev-request@dpdk.org?subject=subscribe>
Errors-To: dev-bounces@dpdk.org
Sender: "dev" <dev-bounces@dpdk.org>
On 2020-04-27 15:20 GMT+0300 Fady Bader wrote:
> Implemented the needed Windows eal timer functions.
[snip]
> +void
> +rte_delay_us_sleep(unsigned int us)
> +{
> + HANDLE timer;
> + LARGE_INTEGER li_due_time;
Here usually comes a blank line.
> + /* create waitable timer */
> + timer = CreateWaitableTimer(NULL, TRUE, NULL);
> + if (!timer) {
> + RTE_LOG_WIN32_ERR("CreateWaitableTimer()");
> + rte_errno = ENOMEM;
> + return;
> + }
> +
> + /* set us microseconds time for timer */
> + li_due_time.QuadPart = -(us * 10);
The comment is still misleading.
[snip]
> +uint64_t
> +get_tsc_freq(void)
> +{
> + uint64_t tsc_freq;
> + LARGE_INTEGER Frequency;
> +
> + QueryPerformanceFrequency(&Frequency);
> +
> + /*
> + * Mulitply by 1K to obtain the true frequency of the CPU
> + * it was noted in the MSDN "in many cases, QueryPerformanceFrequency
> + * returns the TSC frequency divided by 1024"
> + */
> + tsc_freq = ((uint64_t)Frequency.QuadPart * 1024);
> +
> + return tsc_freq;
> +}
Extended quote from MSDN:
Cases might exist where QueryPerformanceFrequency doesn't return the
actual frequency of the hardware tick generator. For example, in many
cases, QueryPerformanceFrequency returns the TSC frequency divided by
1024; and on Hyper-V, the performance counter frequency is always 10
MHz when the guest virtual machine runs under a hypervisor that
implements the hypervisor version 1.0 interface. As a result, don't
assume that QueryPerformanceFrequency will return the precise TSC
frequency.
https://docs.microsoft.com/en-us/windows/win32/sysinfo/acquiring-high-resolution-time-stamps
"In many cases" is pretty vague, we can't distinguish such cases.
Here's what I observe on my QEMU guest ("ticks" is Win32 API, "tsc" is RDTSC):
freq = 100000000 Hz # note: 100 MHz, not 10 MHz
delta (ticks) = 100401071 # Sleep(1000)
delta (secs) = 1.004011 # delta (ticks) / freq
delta (tsc) = 3460948332 # roughly CPU clock frequency
tsc / tick = 34.471229
I suggest measuring a real-time delay with rte_get_tsc_cycles() from arch/
as other EALs do when HPET is not available or configured. This is
discouraged by MSDN, but its reasons seem irrelevant for DPDK.
--
Dmitry Kozlyuk