On 17.04.23 21:26, Zi Yan wrote:
On 17 Apr 2023, at 10:20, David Hildenbrand wrote:
On 16.04.23 20:11, Hugh Dickins wrote:
On Tue, 4 Apr 2023, Andrew Morton wrote:
On Mon, 3 Apr 2023 16:18:32 -0400 Zi Yan <zi.yan@xxxxxxxx> wrote:
File folio supports any order and people would like to support flexible orders
for anonymous folio[1] too. Currently, split_huge_page() only splits a huge
page to order-0 pages, but splitting to orders higher than 0 is also useful.
This patchset adds support for splitting a huge page to any lower order pages
and uses it during file folio truncate operations.
This series (and its v1 & v2) don't appear to have much in the way of
detailed review. As it's at v3 and has been fairly stable I'll queue
it up for some testing now, but I do ask that some reviewers go through
it please.
Andrew, please don't let this series drift into 6.4-rc1.
I've seen a bug or two (I'll point out in response to those patches),
but overall I don't see what the justification for the series is: done
because it could be done, it seems to me, but liable to add surprises.
The cover letter says "splitting to orders higher than 0 is also useful",
but it's not clear why; and the infrastructure provided seems unsuited
to the one use provided - I'll say more on that truncation patch.
I agree. Maybe this patch set is something we want to have in the future once actual consumers that can benefit are in place, such that we can show actual performance numbers with/without.
Ryan is working on large folio for anonymous pages and has shown promising performance
results[1]. This patchset would avoid getting base pages during split if possible.
Yes, I know. And it would be great to get some actual numbers
with/without your patches to show that this optimization actually
matters in practice.
Unrelated, your cover letter mentions "file folio truncate operations.".
Would it also apply to FALLOC_FL_PUNCH_HOLE, when partially zapping a THP?
Until then, "365 insertions(+), 68 deletions(-)" certainly needs some reasonable motivation.
Come on. 225 out of 365 insertions are self tests code. We need motivation to add
testing code?
Well, if you add feature X and the tests target feature X, then
certainly having the tests require the same motivation as feature X. But
yeah, the actual kernel code change is smaller than it looks at first sight.
--
Thanks,
David / dhildenb
