On Fri, Mar 12, 2021 at 04:41:55PM +0100, Peter Weber wrote: > Thank you Matthew! > > > Am 2021-03-12 16:15, schrieb Matthew Wilcox: > > The wikipedia diagram is wrong. Anonymous memory is not handled by the > > page cache. > > Is it roughly right to say, that the virtual memory uses page tables to > handle anonymous memory? I tend to deal with page cache and not anonymous memory, so I'm not sure exactly how someone who's an expert would phrase it. Anonymous pages are "handled" in a number of different ways -- they can be found on LRU lists and they can be found through the page tables. It's all a bit ad-hoc as far as I can tell ;-) > > Anonymous pages enter the storage stack via swap; they are > > found in the page tables, sent to the swap cache and then written to > > swap devices or swap files. Filesystems may get involved at that point, > > but not always. > > And the page cache doesn't handle anonymous memory - even when it is > swapped? Right. There's a swap cache, but that's not the same thing as the page cache. > > There are other weird things in the wikipedia diagram, like Direct I/O > > being seemingly detached from applications, and not appearing to pass > > through the VFS. > > I'm not an expert. Maybe I should add at least note about that on Wikipedia? Maybe!
