Jun'ichi Nomura [j-nomura@xxxxxxxxxxxxx] wrote: > >> Defaults are layered. For current minio, we have : > >> [1] one top level default (hardcoded, superseded by config) > >> [2] per hardware default (hardcoded, superseded by config) > >> [3] per multipath value (none hardcoded, defined by config) > >> > >> You suggest multipath-tools to adapt only the top level minio default > >> depending on dm-rq availability [1], but what of the hwtable defaults > >> [2] ? Should we provide vendors with a way to describe a with-rq minio > >> default *and* a without-rq minio default (a new parameter in the hwentry > >> struct) ? If so, we should also provide a new config file keyword to > >> override this new hwentry parameter hardcoded value ... then the > >> reasoning cascades to the mpentry struct minio setting [3]. > >> > >> Actually, [1] is hardly the common case : only unknown hardware resort > >> to these defaults. > > Do we really need [2]? > > Currently, there seem only 3 minio values in per-hardware default: > - 1000 (DEFAULT_MINIO) > - 128 > - 100 > > I think both 128 and 100 are based on that, in many systems/cases, > max request size (max_sectors) is 512KB and BIO submission > is done in page-size unit (4KB). > > If there isn't strong reason for the current default (1000) > (and I think there isn't), it seems we can remove [2] > after changing the default to 128 (or 100). > > > 1. Set DEFAULT_MINIO to -1 > > 2. If bio based mapping and the value is -1, set it to 1000 > > (DEFAULT_BIO_MINIO) > > 3. If request based mapping, set it to DEFAULT_REQUEST_MINIO. > > Does it mean users can't change rr_min_io value for request-based dm? > I suspect it is possible that someone wants to set non-default > value to minio for request-based dm. Your reading is correct that my proposal doesn't allow it. If we get away with [2] above (hwatable.c based values), then we can have something like this: 1. Remove it from hwentry structure or set it to -1 2. If rr_minio is specified in the conf file (either through default or device section etc), use it. 3. If not specified in the config file, use DEFAULT_BIO_MINIO or DEFAULT_REQUEST_MINIO based on the multipath module version. In other words, every device out there uses DEFAULT_BIO_MINIO or DEFAULT_REQUEST_MINIO if not specified by the administrator. Admin can override it in /etc/multipath.conf file. CON: No per device controller default (aka hwtable entry value) Thanks, Malahal. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
