Mike Snitzer <snitzer@xxxxxxxxxx> writes: > On Mon, May 11 2020 at 12:39pm -0400, > Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx> wrote: > >> Hi, >> >> This fourth version of HST applies the suggestion from Mikulas Patocka >> to do the ktime_get_ns inside the mpath map_bio instead of generic >> device-mapper code. This means that struct dm_mpath_io gained another >> 64bit field. For the request-based case, we continue to use the block >> layer start time information. >> >> With this modification, I was able obtain similar performance on BIO >> to request-based multipath with HST on the benchmarks shared in v1. >> >> v3: https://www.redhat.com/archives/dm-devel/2020-April/msg00308.html >> v2: https://www.redhat.com/archives/dm-devel/2020-April/msg00270.html >> v1: https://www.redhat.com/archives/dm-devel/2020-April/msg00176.html > > I already staged your v3 in linux-next. Please provide an incremental > patch that layers on this git branch: > > https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/log/?h=dm-5.8 > > I was hopeful for a flag to be set (e.g. in 'struct path_selector') to > reflect whether the path selector expects highres start_time. Makes > little sense to incur that extra cost of providing the time if the path > selector doesn't even use it. > > Alternatively, could split out the setting of the time needed by .end_io > to a new path_selector_type method (e.g. .set_start_time). And then > only use ktime_get_ns() for bio-based if .set_start_time is defined. > Would get a little fiddly needing to make sure a stale start_time isn't > used... also, makes more sense to conditionally call this > .set_start_time just after .start_io is. Oh, my apologies, I hadn't noticed it was merged. I will make the time fetch conditional and submit a new patch based on that branch. Thanks, -- Gabriel Krisman Bertazi -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
