>>>>> "Mike" == Mike Snitzer <snitzer@xxxxxxxxxx> writes: Mike, >> However, doesn't it make more sense to tweak limits on DM device >> instead of the underlying ones? It seems a bit counter-intuitive to >> me to change max_sectors_kb on a different device than the one where >> the filesystem whose max I/O size you want to change is located. Mike> As you know, the limits are stacked from the bottom-up. Yep, but since max_sectors_kb is a performance tunable and not something enforced by the hardware, maybe we should consider treating it differently? Mike> As the commit header from this thread mentioned, what I've arrived Mike> at is to have multipathd establish a desired max_sectors_kb (if Mike> configured to do so in multipath.conf) on the underlying paths Mike> _before_ the multipath device is created. Yet to check with Ben Mike> Marzinski or others but it seems like a reasonable feature (and Mike> really the cleaniset way to deal with this issue IMHO.. no need Mike> for lots of kernel code changes for something so niche). That's fine. Another option would be to use the max_dev_sectors queue limit to contain the minimum max_sectors from below. It was really only envisioned as a LLD limit but it may be useful in this case. queue_max_sectors_store() already enforces it. -- Martin K. Petersen Oracle Linux Engineering -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
