On Sat, Jun 03, 2017 at 11:49:01PM -0600, Warner Losh wrote: > > Netflix runs MAXPHYS of 8MB. There's issues with something this big, to be > > sure, especially on memory limited systems. Lots of hardware can't do this > > big an I/O, and some drivers can't cope, even if the underlying hardware > > can. Since we don't use such drivers at work, I don't have a list handy > > (though I think the SG list for NVMe limits it to 1MB). 128k is totally > > reasonable bump by default, but I think going larger by default should be > > approached with some caution given the overhead that adds to struct buf. > > Having it be a run-time tunable would be great. > > > > Of course 128k is reasonable, it's the current default :). I'd mean to say > that doubling would have a limited impact. 1MB might be a good default, but > it might be too big for smaller systems (nothing says it has to be a MI > constant, though). It would be a perfectly fine default if it were a > tunable.
Some cloud providers limit IOPs per VM, for this cases MAXPHYS must be large as posible. _______________________________________________ freebsd-current@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"
