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Lunev" Subject: Re: [PATCH 0/2] block: add logging facility for long standing IO requests Message-ID: <20200731102531.GC177875@stefanha-x1.localdomain> References: <20200710172711.8059-1-den@openvz.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="0vzXIDBeUiKkjNJl" Content-Disposition: inline In-Reply-To: <20200710172711.8059-1-den@openvz.org> Received-SPF: pass client-ip=2a00:1450:4864:20::444; envelope-from=stefanha@gmail.com; helo=mail-wr1-x444.google.com X-detected-operating-system: by eggs.gnu.org: No matching host in p0f cache. That's all we know. X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Vladimir Sementsov-Ogievskiy , qemu-devel@nongnu.org, qemu-block@nongnu.org, Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" --0vzXIDBeUiKkjNJl Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Jul 10, 2020 at 08:27:09PM +0300, Denis V. Lunev wrote: > There are severe delays with IO requests processing if QEMU is running in > virtual machine or over software defined storage. Such delays potentially > results in unpredictable guest behavior. For example, guests over IDE or > SATA drive could remount filesystem read-only if write is performed > longer than 10 seconds. >=20 > Such reports are very complex to process. Some good starting point for th= is > seems quite reasonable. This patch provides one. It adds logging of such > potentially dangerous long IO operations. >=20 > Signed-off-by: Denis V. Lunev > CC: Vladimir Sementsov-Ogievskiy > CC: Kevin Wolf > CC: Max Reitz If I understand correctly this only reports completed I/Os, so if the host hasn't given up on an I/O request yet then QEMU will not report it is taking a long time. In the meantime the guest could start printing timeout errors. I think this patch series is good as it is. In the future maybe a QMP command that lists in-flight I/O requests would be nice. That helps when troubleshooting I/Os that are hung. Stefan --0vzXIDBeUiKkjNJl Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAl8j8ZsACgkQnKSrs4Gr c8itIgf9FFqGu9Shq78udz1uJ6Vc2RU+TtAShwvQj/sE/5r3fvZrHWE55wnDG552 apYsNSUSIiCYVvOV/KvGTwwYBSZeMleKAY12g0jgQ7AykxORUMVSR3pV2yO1X5I2 Lrz7pC5d/8RqMaoaDg1SKOuyptjoTv5x3ota09KdtIGSOwOZbb+iiJOqcISu7K3i HI9wAWksbL81AkRC/Oei4yzPio/mbunN5GhKSklH7GTCsxx8xVdI+/R0GStIRL1x IlIyJNgvyk52aXCrj9o6WQJLLirb9hTrQxL0pZ6tN44pNyNQVVhawERVpYemxvz0 75nohA6TtuKO8csmsYXDyvlws7/ZWQ== =mzjR -----END PGP SIGNATURE----- --0vzXIDBeUiKkjNJl--