On Mon, 10 Nov 2008, Christoph Hellwig wrote: > On Mon, Nov 10, 2008 at 08:11:51AM -0500, Mikulas Patocka wrote: > > For upstream Linux developers: you are holding a spinlock and calling > > bdi*_congested functions that can take indefinite amount of time (there > > are even users reporting having 50 disks in one logical volume or so). I > > think it would be good to move these calls out of spinlocks. > > Umm, they shouldn't block that long, as that completely defeats their > purpose. These functions are mostly used to avoid throwing more I/O at > a congested device if pdflush could do more useful things instead. But > if it blocks in those functions anyway we wouldn't have to bother using > them. Do you have more details about the uses cases when this happens > and where the routines spend so much time? For device mapper, congested_fn asks every device in the tree and make OR of their bits --- so if the user has 50 devices, it asks them all. For md-linear, md-raid0, md-raid1, md-raid10 and md-multipath it does the same --- asking every device. If you have a better idea how to implement congested_fn, say it. Mikulas -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
