On 05/12/15 06:10 AM, Pavel Machek wrote: > On Wed 2015-11-04 10:25:54, Minchan Kim wrote: >> MADV_FREE is on linux-next so long time. The reason was two, I think. >> >> 1. MADV_FREE code on reclaim path was really mess. > > Could you explain what MADV_FREE does? > > Comment in code says 'free the page only when there's memory > pressure'. So I mark my caches MADV_FREE, no memory pressure, I can > keep using it? And if there's memory pressure, what happens? I get > zeros? SIGSEGV? You get zeroes. It's not designed for that use case right now. It's for malloc implementations to use internally. There would need to be a new feature like MADV_FREE_UNDO for it to be usable for caches and it may make more sense for that to be a separate feature entirely, i.e. have a different flag for marking too (not sure) since it wouldn't need to worry about whether stuff is touched.
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