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It's actually quite consistent to have >>>> that output >>>> in smaps the way it is. You mapped a file at an offset, and it >>>> behaves like >>>> an anonymous mapping apart from that. >>>> >>>> Not sure if the buggy khugepaged thing is a good indicator to >>>> warrant this >>>> change. >>> >>> Yeah, this is a user-facing fundamental change that hides >>> information and >>> defies expectation so I mean - it's a no go really isn't it? >>> >>> I'd rather we _not_ make this anon though, because isn't life confusing >>> enough David? I thought it was bad enough with 'anon, file and lol >>> shmem' >>> but 'lol lol also /dev/zero' is enough to make me want to frolick in >>> the >>> fields... >> >> I recall there are users that rely on this memory to get the shared >> zeropage on reads etc (in comparison to shmem!), so I better not ... >> mess with this *at all* :) > > Heh, and I recall reading something about odd behavior of /dev/zero > and some interesting history [1]. > > " > Unlike /dev/null, /dev/zero may be used as a source, not only as a > sink for data. All write operations to /dev/zero succeed with no other > effects. However, /dev/null is more commonly used for this purpose. > > When /dev/zero is memory-mapped, e.g., with mmap, to the virtual > address space, it is equivalent to using anonymous memory; i.e. memory > not connected to any file. > " > > "equivalent to using anonymous memory" is interesting. For private mapping. Shared mapping is equivalent to shmem. > > > Also, /dev/zero was there before MAP_ANONYMOUS was invented according > to [1], which is quite interesting. Interesting... Didn't know this before. > > ... so this is anonymous memory as "real" as it can get :) Let's make /dev/zero as real as anonymous memory :) > > > [1] https://en.wikipedia.org/wiki//dev/zero >