On Mon, 8 Mar 2021 18:50:02 +0000 Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote: > Hi Andrew, > > You have a patch in your tree which I think is a bad idea. > Link: http://lkml.kernel.org/r/1558073209-79549-1-git-send-email-chenjianhong2@xxxxxxxxxx > > The problem it describes is real -- if you chew up all the address > space with 64MB pages, free one and then try to allocate another one, it > will fail. I don't like the solution, though. If memory is fragmented > in a different way from that described by the patch, it will cause us > to walk into rbtree nodes that look like they might be able to satisfy > our allocation, only to find that they cannot, due to alignment issues. > In the worst case, it turns into a linear scan of the address space > instead of logarithmic. > > I would prefer to see this solved by doing two passes. The first would > look for a 128MB size hole, as we do now, which is guaranteed to find > us a 64MB hole if it succeeds. If that search fails, then we can fall > back to the 64MB hole search, as done in this patch. OK, thanks. The patch is very old, and stuck. I'll drop it.
