On Fri, Sep 15, 2023 at 05:36:27PM +0200, David Hildenbrand wrote: > On 15.09.23 17:34, Matthew Wilcox wrote: > > No, it can't. This patchset triggers only on write, not on read or page > > fault, and it's conservative, so it will only allocate folios which are > > entirely covered by the write. IOW this is memory we must allocate in > > order to satisfy the write; we're just allocating it in larger chunks > > when we can. > > Oh, good! I was assuming you would eventually over-allocate on the write > path. We might! But that would be a different patchset, and it would be subject to its own discussion. Something else I've been wondering about is possibly reallocating the pages on a write. This would apply to both normal files and shmem. If you read in a file one byte at a time, then overwrite a big chunk of it with a large single write, that seems like a good signal that maybe we should manage that part of the file as a single large chunk instead of individual pages. Maybe. Lots of things for people who are obsessed with performance to play with ;-)
