On 10/07/2013 04:54 PM, John Stultz wrote: >>> >> And wouldn't this apply to MADV_DONTNEED just as well? Perhaps what we >> should do is an enhanced madvise() call? > Well, I think MADV_DONTNEED doesn't *have* do to anything at all. Its > advisory after all. So it may immediately wipe out any data, but it may not. > > Those advisory semantics work fine w/ VRANGE_VOLATILE. However, > VRANGE_NONVOLATILE is not quite advisory, its telling the system that it > requires the memory at the specified range to not be volatile, and we > need to correctly inform userland how much was changed and if any of the > memory we did change to non-volatile was purged since being set volatile. > > In that way it is sort of different from madvise. Some sort of an > madvise2 could be done, but then the extra purge state argument would be > oddly defined for any other mode. > > Is your main concern here just wanting to have a zero-fill mode with > volatile ranges? Or do you really want to squeeze this in to the madvise > call interface?
The point is that MADV_DONTNEED is very similar in that sense, especially if allowed to be lazy. It makes a lot of sense to permit both scrubbing modes orthogonally. The point you're making has to do with withdrawal of permission to flush on demand, which is a result of having the lazy mode (ongoing permission) and having to be able to withdraw such permission. -0hpa -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/