On Tue, 2016-02-16 at 16:28 +1100, Dave Chinner wrote: > On Mon, Feb 15, 2016 at 03:52:31PM -0800, Daniel Walker wrote: > > On 02/15/2016 03:05 PM, Dave Chinner wrote: > > > > > > As for a replacement, looking at what pages you consider > > > "droppable" > > > is really only file pages that are not under dirty or under > > > writeback. i.e. from /proc/meminfo: > > > > > > Active(file): 220128 kB > > > Inactive(file): 60232 kB > > > Dirty: 0 kB > > > Writeback: 0 kB > > > > > > i.e. reclaimable file cache = Active + inactive - dirty - > > > writeback. > ..... > > > As to his other suggestion of estimating the droppable cache, I > > have considered it but found it unusable. The problem is the > > inactive file pages count a whole lot pages more than the > > droppable pages. > > inactive file pages are supposed to be exactly that - inactive. i.e. > the have not been referenced recently, and are unlikely to be dirty. > They should be immediately reclaimable. Inactive file pages can still be mapped by processes. The reason we do not unmap file pages when moving them to the inactive list is that some workloads fill essentially all of memory with mmapped file pages. Given that the inactive list is generally a considerable fraction of file memory, unmapping pages that get deactivated could create a lot of churn and unnecessary page faults for that kind of workload. -- All rights reversed
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