> With a binary interface like an ioctl I can see how you could have extra > unused fields which you can ignore now and let people start adding extra > options like the range in the future. Yes, ioctl is another possibility. But I would argue that sysctl is more convenient interface, because idea of sdrop_caches is similar to drop_caches's one and it is convenient to have these interfaces in the same place. But if sdrop_caches uses procfs it seems that there is no easy way to pass parameters of different types in one write operation. > Other questions I'd ask would be - how about the access control model? > Will only root be able to drop caches? Why can't I drop caches for my > own file? Access control model is the same as for drop_caches. This means that only root can write to this file. But it is easy to add a feature that allows any user to clean page cache of inodes that this user owns. 2014-06-25 15:42 GMT+02:00 Artem Bityutskiy <dedekind1@xxxxxxxxx>: > On Wed, 2014-06-25 at 15:23 +0200, Thomas Knauth wrote: >> On Wed, Jun 25, 2014 at 11:56 AM, Artem Bityutskiy <dedekind1@xxxxxxxxx> wrote: >> > Thanks for the answer, although you forgot to comment on the question >> > about possibly extending the new interface to work with file ranges in >> > the future. For example, I have a 2 TiB file, and I am only interested >> > in dropping caches for the first couple of gigabytes. Would I extend >> > your interface, or would I come up with another one? >> >> Ah, didn't quite understand what was meant with file ranges. Again, we >> had not considered this so far. I guess you could make a distinction >> between directories and files here. If the path points to a file, you >> can have an optional argument indicating the range of bytes you would >> like to drop. Something like >> >> echo "my-file 0-1000,8000-1000" > /proc/sys/vm/sdrop_cache >> >> If this is desirable, we can add it to the patch. > > With a binary interface like an ioctl I can see how you could have extra > unused fields which you can ignore now and let people start adding extra > options like the range in the future. > > With this kind of interface I am not sure how to do this. > > Other questions I'd ask would be - how about the access control model? > Will only root be able to drop caches? Why can't I drop caches for my > own file? > > I did not put much thinking into this, but it looks like ioctl could be > a better interface for the task you are trying to solve... > > Sorry if I am a bit vague, I am mostly trying to make you guys give this > more thoughts, and come up with a deeper analysis. Interfaces are very > important to get right, or as right as possible... > > -- > Best Regards, > Artem Bityutskiy > -- Regards, Maksym Planeta. -- 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
