On Mon, Jun 21, 2010 at 08:56:55PM +0200, Jens Axboe wrote: > FWIW, Windows marks meta data writes and they go out with FUA set > on SATA disks. And SATA firmware prioritizes FUA writes, it's essentially > a priority bit as well as a platter access bit. So at least we have some > one else using a meta data boost. I agree that it would be a lot more > trivial to add the annotations if they didn't have scheduler impact > as well, but I still think it's a sane thing. And we still disable the FUA bit in libata unless people set a non-standard module option.. > >> Reads are sync by nature in the block layer, so they don't get that > >> special annotation. > > > > Well, we do give them this special annotation in a few places, but we > > don't actually use it. > > For unplugging? We use the explicit unplugging, yes - but READ_META also includes REQ_SYNC which is not used anywhere. > > But that leaves the question why disabling the idling logical for > > data integrity ->writepage is fine? This gets called from ->fsync > > or O_SYNC writes and will have the same impact as O_DIRECT writes. > > We have never enabled idling for those. O_SYNC should get a nice > boost too, it just needs to be benchmarked and tested and then > there would be no reason not to add it. We've only started using any kind of sync tag last year in ->writepage in commit a64c8610bd3b753c6aff58f51c04cdf0ae478c18 "block_write_full_page: Use synchronous writes for WBC_SYNC_ALL writebacks", switching from WRITE_SYNC to WRITE_SYNC_PLUG a bit later in commit 6e34eeddf7deec1444bbddab533f03f520d8458c "block_write_full_page: switch synchronous writes to use WRITE_SYNC_PLUG" Before that we used plain WRITE, which had the normal idling logic. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
