On Sat, Mar 29 2014 at 4:11am -0400, Milan Broz <gmazyland@xxxxxxxxx> wrote: > On 03/28/2014 09:11 PM, Mike Snitzer wrote: > > From: Mikulas Patocka <mpatocka@xxxxxxxxxx> > > > > Write requests are sorted in a red-black tree structure and are submitted > > in the sorted order. > > > > In theory the sorting should be performed by the underlying disk scheduler, > > however, in practice the disk scheduler accepts and sorts only 128 requests. > > In order to sort more requests, we need to implement our own sorting. > > Hi, > > I think it would be nice to mention why simply increasing queue nr_request > doesn't help. It is definitely not limited to 128, it is only default value. > > (I just wonder how this helps for SSDs where I think it depends what's fw > doing with io requests anyway). Obviously is less of a concern on SSD but I think we'll find it still is beneficial. > It would be nice to have sysfs switch to disable sorting in dmcrypt but that > can be added later. Not sure sysfs is the right place to put this. Would prefer to use a DM message to toggle it. And possibly default to off if the backing storage is non-rotational. > Anyway, thanks for rebasing these patches! > > ... > > +#define io_node rb_entry(parent, struct dm_crypt_io, rb_node) > > + if (sector < io_node->sector) > > + p = &io_node->rb_node.rb_left; > > + else > > + p = &io_node->rb_node.rb_right; > > +#undef io_node > > Btw, could this be switched to inline function instead of define, > or it is only me who thinks #define here is ugly? :) I wasn't a big fan of the #define .. #undef but I didn't see the need to change it if Mikulas felt more comfortable with it this way. I recently wrote some rbtree code for dm-thinp, it also uses a #define but outside of the function body (above the function), see: https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=for-next&id=a43260f01a3b6f5ef33d0abc86e9b0a92096cd84 We could change this code in a similar way. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
