Date: Fri, 15 Apr 2016 12:26:17 -0400 From: Allan Jude <allanjude@freebsd.org> To: freebsd-current@freebsd.org Subject: Re: Heads up Message-ID: <57111629.6070606@freebsd.org> In-Reply-To: <CAH7qZftspY=i5MaQ6sNg5L5XXBN7gfCuAMO-NZt=7Qp5zo6u_w@mail.gmail.com> References: <CANCZdfpnYnVrvhNagYUT9RhAuC1AMCrxh=GCt8RKT0bqxuJybw@mail.gmail.com> <CAH7qZftspY=i5MaQ6sNg5L5XXBN7gfCuAMO-NZt=7Qp5zo6u_w@mail.gmail.com>
next in thread | previous in thread | raw e-mail | index | archive | help
This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --kUTTLi1D2VgF4kr7qkhrnOjaDsPvJMrIb Content-Type: multipart/mixed; boundary="cFhrscBwWNNmCPnKdqIPpAUlrkEk5s9vv" From: Allan Jude <allanjude@freebsd.org> To: freebsd-current@freebsd.org Message-ID: <57111629.6070606@freebsd.org> Subject: Re: Heads up References: <CANCZdfpnYnVrvhNagYUT9RhAuC1AMCrxh=GCt8RKT0bqxuJybw@mail.gmail.com> <CAH7qZftspY=i5MaQ6sNg5L5XXBN7gfCuAMO-NZt=7Qp5zo6u_w@mail.gmail.com> In-Reply-To: <CAH7qZftspY=i5MaQ6sNg5L5XXBN7gfCuAMO-NZt=7Qp5zo6u_w@mail.gmail.com> --cFhrscBwWNNmCPnKdqIPpAUlrkEk5s9vv Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable On 2016-04-15 12:13, Maxim Sobolev wrote: > Great, work Warner, thanks! Small note, though. The CAM_IOSCHED_NETFLIX= > seems like a quite poor name for a kernel option. IMHO there is no good= > reason for polluting it with the name of the company that sponsored the= > development. I don't think we have any precedents of doing this unless = the > option is related to a piece of hardware that the company makes, and it= 's > not the case here. Apart from "coolness" factor as far as I understand = that > _NETFLIX suffix does not give any tangible benefit for anybody reading > kernel config and trying to understand what this option actually does. > CAM_IOSCHED_SSDNG or something would be better IMHO. Just my $0.02. >=20 > -Max The tuning that CAM_IOCHED_NETFLIX does is not generally applicable to all SSDs, it is very specific to netflix style workloads, where you want to rate-limit writes to preserve low latency for reads. Most workflows, like a database on an SSD, will be the opposite, wanting to prioritize writes over anything else. It is important to not give this scheduler a generic attractive name that will cause people to use it without understanding what its purpose is. The purpose is not 'better scheduling for SSDs', but rather 'scheduling for a latency sensitive read-mostly workload while updating a content library in the background' >=20 > On Thu, Apr 14, 2016 at 3:42 PM, Warner Losh <imp@bsdimp.com> wrote: >=20 >> The CAM I/O scheduler has been committed to current. This work is desc= ribed >> in https://people.freebsd.org/~imp/bsdcan2015/iosched-v3.pdf though th= e >> default scheduler doesn't change the default (old) behavior. >> >> One possible issue, however, is that it also enables NCQ Trims on ada = SSDs. >> There are a few rogue drives that claim support for this feature, but >> actually implement data corrupt instead of queued trims. The list of k= nown >> rogues is believed to be complete, but some caution is in order. >> >> Warner --=20 Allan Jude --cFhrscBwWNNmCPnKdqIPpAUlrkEk5s9vv-- --kUTTLi1D2VgF4kr7qkhrnOjaDsPvJMrIb Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (MingW32) iQIcBAEBAgAGBQJXERYsAAoJEBmVNT4SmAt+OcMQAK/2Tq5TS3FXCDF+h7vv1Ivu rhbz6nDHeb0Uf7RwVP9ZreOJ49kTvVkLWgWontr6bjKLBE37YyVPN82aLDYpw9yB +wLcWzde/Pgz6+qoDX2Atbn2DzGQFPyRFNb0HiAaC5NnrGvaHEon+GlE8ZMsyZOM Ro7L1mfUP9dAImi1Ie9Tn2h5E0irbWhnAgfL813ldCTTLuTMWQHhCCisDQDjfmHq BVxyq6+wjkDaUUCoMSTfpep/snfac4eCJvFgMHZ4+Q0fRqUNx+Ar6OjpTtPGdKim TmUOnob0QxgqpQX0jL/aQV3ceenCv/PXj4bbftCMxMoInMd/txtcndUz0e01sF4H ZCuwlQEuqOPwIQ5vUidfG9t5o1z5znE1BkfS9yj1xjrcsoxe7cVYO3XH+Ur2aThj 3rJjAz4adjEk1WTxGxYgLjk4ZvJZBCxbiGwLzVSUFaaCEfq3Th5iW6C/QEIc1RnD L8mhAwFDkPONAizk4lpLlzicWDmnStEdzs/TzpMxDhiNNY2YYZbGWwCBTBMCqyna ZNGdiz8tj2jS0uGvDEFA3ms1aw0iDslc7p+/DP++WdWiini2N2YFxnDDw3Mf529m 3m6EhLUr24h+kt2ktHksv1iEr10RZyXNUkifLZbN9p1+w+clhpoyCmVcWCdbnDpw y3cMrDUoCAfCV9sZA8ND =LtAH -----END PGP SIGNATURE----- --kUTTLi1D2VgF4kr7qkhrnOjaDsPvJMrIb--
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?57111629.6070606>