On Wed, 29.09.10 16:25, Ric Wheeler (rwheeler@xxxxxxxxxx) wrote: > >This in fact is how all current readahead implementations work, be it > >the fedora, the suse or ubuntu's readahead or Arjan's sreadahead. What's > >new is that in the systemd case we try to test for ssd/rotating > >properly, instead of just hardcoding a check for > >/sys/class/block/sda/queue/rotational. > > > > A couple of questions pop into mind - is systemd the right place to > automatically tune readahead? If this is a generic feature for the > type of device, it sounds like something that we should be doing > somewhere else in the stack (not relying on tuning from user space). Note that this is not the kind of readahead that is controllable via /sys/class/block/sda/queue/read_ahead_kb, this is about detecting "hot" files at boot, and then preloading them on the next boot. i.e. the problem Jens once proposed fcache for. > Second question is why is checking in /sys a big deal, would you > prefer an interface like we did for alignment in libblkid? Well, currently there's no way to discover the underlying block devices if you have a btrfs mount point. This is what Josef's patch added for us. Lennart -- Lennart Poettering - Red Hat, Inc. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
