On Wed, May 29, 2013 at 12:57:47PM -0700, Andrew Morton wrote: > On Wed, 29 May 2013 14:50:27 -0500 Seth Jennings <sjenning@xxxxxxxxxxxxxxxxxx> wrote: > > > On Wed, May 29, 2013 at 11:29:29AM -0700, Andrew Morton wrote: > > > On Wed, 29 May 2013 09:57:20 -0500 Seth Jennings <sjenning@xxxxxxxxxxxxxxxxxx> wrote: > > > > > > > > > +/********************************* > > > > > > +* helpers > > > > > > +**********************************/ > > > > > > +static inline bool zswap_is_full(void) > > > > > > +{ > > > > > > + return (totalram_pages * zswap_max_pool_percent / 100 < > > > > > > + zswap_pool_pages); > > > > > > +} > > > > > > > > > > We have had issues in the past where percentage-based tunables were too > > > > > coarse on very large machines. For example, a terabyte machine where 0 > > > > > bytes is too small and 10GB is too large. > > > > > > > > Yes, this is known limitation of the code right now and it is a high priority > > > > to come up with something better. It isn't clear what dynamic sizing policy > > > > should be used so, until such time as that policy can be determined, this is a > > > > simple stop-gap that works well enough for simple setups. > > > > > > It's a module parameter and hence is part of the userspace interface. > > > It's undesirable that the interface be changed, and it would be rather > > > dumb to merge it as-is when we *know* that it will be changed. > > > > > > I don't think we can remove the parameter altogether (or can we?), so I > > > suggest we finalise it ASAP. Perhaps rename it to > > > zswap_max_pool_ratio, with a range 1..999999. Better ideas needed :( > > > > zswap_max_pool_ratio is fine with me. I'm not entirely clear on the change > > though. Would that just be a name change or a change in meaning? > > It would be a change in behaviour. The problem which I'm suggesting we > address is that a 1% increment is too coarse. Sorry, but I'm not getting this. This zswap_max_pool_ratio is a ratio of what to what? Maybe if you wrote out the calculation of the max pool size using this ratio I'll get it. Seth -- 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>