On Wed, Nov 20, 2013 at 12:52:47PM -0500, Dan Streetman wrote: > On Wed, Nov 20, 2013 at 12:33 PM, Vladimir Murzin <murzin.v@xxxxxxxxx> wrote: > > Hi Dan! > > > > On Wed, Nov 20, 2013 at 11:38:42AM -0500, Dan Streetman wrote: > >> The "compressor" and "enabled" params are currently hidden, > >> this changes them to read-only, so userspace can tell if > >> zswap is enabled or not and see what compressor is in use. > > > > Could you elaborate more why this pice of information is necessary for > > userspace? > > For anyone interested in zswap, it's handy to be able to tell if it's > enabled or not ;-) Technically people can check to see if the zswap > debug files are in /sys/kernel/debug/zswap, but I think the actual > "enabled" param is more obvious. And the compressor param is really > the only way anyone from userspace can see what compressor's being > used; that's helpful to know for anyone that might want to be using a > non-default compressor. So, it is needed for user not userspace? I tend to think that users are smart enough to check cmdline for that. AFAICS module_param exist here to provide simplest ability to handle the setting via cmdline. zsawap is not able to be loaded as a module for now. If it could, than there was reason to check which params were used while module loading and guess how they affected zswap state. > > And of course, eventually we'll want to make the params writable, so > the compressor can be changed dynamically, and zswap can be enabled or > disabled dynamically (or at least enabled after boot). module_params is not the best place to handle this, because they do not provide any hooks for handling write unless I missed something. However, making zswap state dynamically adjustable require not only setting the numbers, but handling the correctness switching from one state to another. Vladimir -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>