From: Patrick Williams <patrick@stwcx.xyz>
To: Nguyen Chanh <nguyenchanh2201@gmail.com>
Cc: openbmc@lists.ozlabs.org
Subject: Re: [c++] [hwmon] std::ifstream read file with timeout so long
Date: Wed, 7 Oct 2020 10:24:28 -0500 [thread overview]
Message-ID: <20201007152428.GJ6152@heinlein> (raw)
In-Reply-To: <CAPGDkaHzu5UOES-irDLtu9jwLULyX9_BWAX7rgTPiaeXOT2ByA@mail.gmail.com>
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On Tue, Oct 06, 2020 at 10:42:18PM +0700, Nguyen Chanh wrote:
> In https://github.com/openbmc/phosphor-hwmon => hwmonio.cpp , I saw we use
> the std::ifstream to open and read a device sensor.
>
> But, I met an issue with it. In case the sensor was disabled (Ex: the Fan
> was unplugged), the std::ifstream read will take a long time . The timeout
> in there is so long. It makes my system have a BIG delay in each checking
> sensor.
>
> Other observation : In case the sensor device is ready, the time for sensor
> reading is expected.
>
> Measuring std::ifstream reading:
>
> In case unplugged sensor: 91385 microseconds
> In case plugged sensor. : 507 microseconds
Do you know which device driver it is interacting with? This sounds
like an issue with the underlying driver. Perhaps it is attempting
too many retries.
>
> The patch to measure the std::ifstream reading, please see attachment !
>
> Unexpected behavior you saw
>
> The timeout in there is so long
>
> Expected behavior
>
> Do we have any better solution in this case? take less more timeout.
> [image: Screen Shot 2020-10-03 at 11.32.36 AM.png]
> --
> *Nguyen Minh Chanh *
> *Embedded Software Engineer *
--
Patrick Williams
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next prev parent reply other threads:[~2020-10-07 15:26 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-06 15:42 [c++] [hwmon] std::ifstream read file with timeout so long Nguyen Chanh
2020-10-07 15:24 ` Patrick Williams [this message]
2020-10-07 19:02 ` Anton Kachalov
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