Hi, On 01/22/11 02:39, Malahal Naineni wrote: > Christophe Varoqui [christophe.varoqui@xxxxxxxxx] wrote: >> >>> I'm not following why we'd need a different configuration parameter. >>> It is just that the default rr_min_io that would be used would be >>> conditional on the multipath target version being >= 1.1.0. >>> >> 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 [1] one top level default (hardcoded, superseded by config) 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 [2] per hardware default (hardcoded, superseded by config) 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). >> Is my reasoning flawed ? > > I don't think so. Your reasoning is right. How about this: > > 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. > > Note that devices can't have individual hardware default for request > based mappings in this method and I think that should be OK. They are > allowed to individual hardware based default for BIO based mappings as > they have now. I will code it up if everyone agrees. 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. Thanks, -- Jun'ichi Nomura, NEC Corporation -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
