Messages in this thread | | | Date | Wed, 29 May 2013 11:29:29 -0700 | From | Andrew Morton <> | Subject | Re: [PATCHv12 3/4] zswap: add to mm/ |
| |
On Wed, 29 May 2013 09:57:20 -0500 Seth Jennings <sjenning@linux.vnet.ibm.com> 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 :(
| |