On 10/08/2015 09:44 PM, Benjamin Marzinski wrote: > Currently, running the alua prioritizer on a path causes 5 ioctls on many > devices. get_target_port_group_support() returns whether alua is > supported. get_target_port_group() gets the TPG id. This often takes two > ioctls because 128 bytes is not a large enough buffer size on many > devices. Finally, get_asymmetric_access_state() also often takes two > ioctls because of the buffer size. This can get to be problematic when > there are thousands of paths. The goal of this patch to to cut this down > to one call in the usual case. > > In order to do this, I've added a context pointer to the prio structure, > similar to what exists for the checker structure, and initprio() and > freeprio() functions to the prioritizers. The only one that currently uses > these is the alua prioritizer. It caches the type of alua support, the TPG > id, and the necessary buffer size. The only thing I'm worried about with > this patch is whether the first two values could change. In order to deal > with that possibility, whenever a path gets a change event, or becomes > valid again after a failure, it resets the context structure values, which > forces all of them to get checked the next time the prioritizer is called. > Hmm. What about reading /sys/block/sdX/device/vpg_pg83 ? That carries the same information, and you would need to call the ioctl only once ... Cheers, Hannes -- Dr. Hannes Reinecke zSeries & Storage hare@xxxxxxx +49 911 74053 688 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton HRB 21284 (AG Nürnberg) -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
