Date: Wed, 9 Sep 2020 10:30:09 +0200 From: Stefan Esser <se@freebsd.org> To: FreeBSD CURRENT <freebsd-current@freebsd.org>, freebsd-fs@freebsd.org Cc: Matthew Macy <mmacy@freebsd.org>, Allan Jude <allanjude@freebsd.org>, Graham Perrin <grahamperrin@gmail.com> Subject: Re: OpenZFS and L2ARC Message-ID: <712aa75b-b8ce-1eb0-ea0e-db1c2b7cc0c2@freebsd.org> In-Reply-To: <fb112996-d713-f7e0-45e3-451d6bc02102@freebsd.org> References: <b8f63e55-4c7e-8be0-7c52-5d8e6cb333f4@freebsd.org> <7d54dc30-b8b1-a127-ec39-9fb759c8a55d@gmail.com> <fb112996-d713-f7e0-45e3-451d6bc02102@freebsd.org>
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This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --4MdWjVcNIaJybu17SUuzQTUZJiNC47eDU Content-Type: multipart/mixed; boundary="psYTM27l8ECy8qY3oI4Tf2QWIP3Ki99ky"; protected-headers="v1" From: Stefan Esser <se@freebsd.org> To: FreeBSD CURRENT <freebsd-current@freebsd.org>, freebsd-fs@freebsd.org Cc: Matthew Macy <mmacy@freebsd.org>, Allan Jude <allanjude@freebsd.org>, Graham Perrin <grahamperrin@gmail.com> Message-ID: <712aa75b-b8ce-1eb0-ea0e-db1c2b7cc0c2@freebsd.org> Subject: Re: OpenZFS and L2ARC References: <b8f63e55-4c7e-8be0-7c52-5d8e6cb333f4@freebsd.org> <7d54dc30-b8b1-a127-ec39-9fb759c8a55d@gmail.com> <fb112996-d713-f7e0-45e3-451d6bc02102@freebsd.org> In-Reply-To: <fb112996-d713-f7e0-45e3-451d6bc02102@freebsd.org> --psYTM27l8ECy8qY3oI4Tf2QWIP3Ki99ky Content-Type: multipart/mixed; boundary="------------0106056A6F82F876FECCBA97" Content-Language: en-US This is a multi-part message in MIME format. --------------0106056A6F82F876FECCBA97 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: quoted-printable Am 09.09.20 um 08:46 schrieb Stefan Esser: > Am 09.09.20 um 00:45 schrieb Graham Perrin: >> Recalling=20 >> <https://lists.freebsd.org/pipermail/freebsd-current/2020-March/075661= =2Ehtml>,=20 >> on 28/03/2020 15:17,28/03/2020 15:17, Allan Jude wrote: >> >> =A0>> =85 >> =A0>> >> =A0>> Basically 'arc' was converted to a subtree. >> =A0>> >> =A0>> We should add some backwards compat sysctls to cover some of >> =A0>> these renames etc so configs and scripts don't break etc. >=20 > This is not possible for quite a number of sysctls, since there is > no simple 1:1 mapping for many of them. >=20 >=20 > And there is an annoyance that I had noticed before but now have > tracked down: >=20 > $ time sysctl kstat.zfs.misc.dbufs | wc > =A0=A0 55327 2047031 16333472 >=20 > real=A0=A0=A0 0m16,446s > user=A0=A0=A0 0m0,055s > sys=A0=A0=A0 0m16,397s >=20 > Somebody decided to put a complete list of dbufs under this sysctl > and thus querying "kstat.zfs.misc" takes that long (16 seconds to > generate 16 MB of output on my system), even if only a few other > values in "kstat.zfs.misc" are needed. >=20 > I do not know whether there is any chance to get that debug output > moved out of the "misc", e.g. into a new "debug" sub-tree. I'm afraid, > that on Linux there are scripts that expect it under this name. >=20 > If it is not acceptable to the upstream, we should locally modify the > sysctl tree to move that variable out of "misc", IMHO. (While not > taking much time, "kstat.zfs.misc.dbgmsg" should also be relocted to > a "debug" sub-tree, IMHO ...) >=20 > zfs-stats needs tens of values from "misc", and if they are not all > added individually to the Kstat array, this will limit the response > time to any zfs-stats invocation. >=20 > It is not too hard to add the new variables in zfs-stats and to > adapt the calculations to derive meaningful values to display. >=20 > But if it always takes 16 seconds to generate any output, I'm not > likely to use it too often ... Update: I have created a fork of zfs-stats to work on: https://github.com/stesser/zfs-stats Initial change is to work around the long delay mentioned above and to use the correct name for the vdev cache size variable and to display the size, data contents and the corresponding compression factor of the compressed L2ARC. I'll create pull requests to inform the upstream of these changes. --------------0106056A6F82F876FECCBA97-- --psYTM27l8ECy8qY3oI4Tf2QWIP3Ki99ky-- --4MdWjVcNIaJybu17SUuzQTUZJiNC47eDU Content-Type: application/pgp-signature; name="OpenPGP_signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="OpenPGP_signature" -----BEGIN PGP SIGNATURE----- wsB5BAABCAAjFqEEo3HqZZwL7MgrcVMTR+u171r99UQFAl9YkpIFAwAAAAAACgkQR+u171r99UQi jQf/WwI9ynTm4OdJazZizYjcq3FCNO4P3usLKgWms3ogCuv8AyssrnmVDBi1/fqfpFqPmjcE7xyF AWgckWJInV40sAXUvTgoCyJDMbrKFPRks/baYJKtRRCS6O73MXHE3yxKnSLY36bXWzYxB9RO1KAP 95jvniY+xsBaLUwsKVl9cilCzxtr4GZWw7XcxWlutVzgGn2DYIoTFp+rd1TJn7Lz3os4NjCNh/6i 7H98SQ7ijrrjfVivDjT1ipQjmJAuoYEXuCDJbPU4e3oB/q3IiQlv3EUkNcdpTmUpb/hcZ0Th8nHL hDzVP1lm8dGDkl26NwKtPpKYcEx1BcgVEMzgm/s6Lw== =8eE1 -----END PGP SIGNATURE----- --4MdWjVcNIaJybu17SUuzQTUZJiNC47eDU--
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