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Received: from localhost (mobile-166-172-120-67.mycingular.net [166.172.120.67]) by mail.messagingengine.com (Postfix) with ESMTPA id B0D4B3280059; Wed, 7 Oct 2020 11:24:29 -0400 (EDT) Date: Wed, 7 Oct 2020 10:24:28 -0500 From: Patrick Williams To: Nguyen Chanh Subject: Re: [c++] [hwmon] std::ifstream read file with timeout so long Message-ID: <20201007152428.GJ6152@heinlein> References: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="3r2sERxeG5twY2zu" Content-Disposition: inline In-Reply-To: X-BeenThere: openbmc@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Development list for OpenBMC List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: openbmc@lists.ozlabs.org Errors-To: openbmc-bounces+openbmc=archiver.kernel.org@lists.ozlabs.org Sender: "openbmc" --3r2sERxeG5twY2zu Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Oct 06, 2020 at 10:42:18PM +0700, Nguyen Chanh wrote: > In https://github.com/openbmc/phosphor-hwmon =3D> hwmonio.cpp , I saw we = use > the std::ifstream to open and read a device sensor. >=20 > 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. >=20 > Other observation : In case the sensor device is ready, the time for sens= or > reading is expected. >=20 > Measuring std::ifstream reading: >=20 > 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. >=20 > The patch to measure the std::ifstream reading, please see attachment ! >=20 > Unexpected behavior you saw >=20 > The timeout in there is so long >=20 > Expected behavior >=20 > 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] > --=20 > *Nguyen Minh Chanh * > *Embedded Software Engineer * --=20 Patrick Williams --3r2sERxeG5twY2zu Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEEBGD9ii4LE9cNbqJBqwNHzC0AwRkFAl993aoACgkQqwNHzC0A wRlPVg/+PMzLzKqhSZeJ1LYChuD/zMqBMj0ffkzlLhXmKscVIXZHQNHopbxZoqev uBd4qp/ZDZ3Xk4nWOucewS8h9P5LfbLseBTiQzcQgArJKTZ3C2INVE1cFZ0P6oI5 x/QmAKzPcQGi/A19kW0enIn+fuaxldEVKfgGL+1dnNr8p1dyTqjsu2ZuZke5CgcU yPOxVu/nJGv1KHBVG4BqQDdGRWFBu+82mvWFJLyl4Vg/ZXlHZiMz06HchVJ4RJVJ xmgHuCnIigMR5uJXnVN8ug130JYrj7fx1KYescVhSO+TN05mzjfJsmMT38EUYz6w s/v85xjCDMZ6vJQXVfiehIGs+Ex8X2nDJPV6Uewp916aa6uTxpPv3UwgdXdvlzN5 oHHo6x2NbUsd71pLNVBm/Hmc/mctbJ3UuGqLe0o4+uULpMiope3nDaEhZVEI2qQ8 WBsf3RFSFmuMUlMawR7cjIrgSv3au8B4n62uvEOXYtCpUQEFXlzKD7NGPpjAFPbB RnYQ9KCen0QJPdFcOHHrwZCgJxKn4M/ezd6rB7IX1Vb3oyxvKrooV6+59rRmNDGg 7R+0fDnQxJwX4jtPjHp1b73A9IxmpR3k2OC+FOx6OIcM+QQ6bFqRYptuIct+b9nZ 8MoCHFI+QMbXIDt6HGfiBG6IwL23ZVY4pmn9MVIkiwAk7lLlTT4= =4Jg2 -----END PGP SIGNATURE----- --3r2sERxeG5twY2zu--