On 2023/11/7 23:34, Gregory Price wrote:
On Tue, Nov 07, 2023 at 09:03:53AM +0800, Kefeng Wang wrote:
On 2023/10/31 12:34, Gregory Price wrote:
On Tue, Oct 31, 2023 at 09:13:44AM +0000, Matthew Wilcox wrote:
On Mon, Oct 30, 2023 at 07:41:23PM -0400, Gregory Price wrote:
On Mon, Oct 30, 2023 at 11:22:18PM +0000, Matthew Wilcox wrote:
On Mon, Oct 30, 2023 at 02:00:05PM -0400, Gregory Price wrote:
kpageflags reads page-flags directly from the page, even when the
respective flag is only updated on the headpage of a folio.
Update bitchecks to use PAGEFLAG() interfaces to check folio for the
referenced, dirty, lru, active, and unevictable bits.
But uptodate, writeback and reclaim (amongst others) are also defined
only on the head page.
Ah yes i was only looking at the things defined w/ PAGEFLAG defines in
page-flags.h. I'll give it full once over can collect them all, my bad.
(also i forgot to update my commit message)
Quick question here since i have your attention: any recommendation on
what to do for ONLY_HEAD flags? If the provided page is not the head,
should the flag report 0... or whatever the head says?
Thinking about it some more, really almost all flags are per-folio, not
per-page. The only exceptions are HWPoison and AnonExclusive. So
probably the right way to do this is to make k = folio->flags, and
then just change a few places rather than changing all the places that
test 'k'.
Funny enough that's what i originally did but was confident it was
correct so walked it back. I'll take another crack at it.
Hi Gregory, any update?
I changed stable_page_flags[1] when try to remove page idle wrapper,
Matthew pointed it will conflict with this, I could redo my patch
based on your new version:)
[1]https://lore.kernel.org/linux-mm/20231103072906.2000381-5-wangkefeng.wang@xxxxxxxxxx/
Thanks.
looks like we were noticing the same thing. I haven't done any further
work, got caught up in another project.
Yes, I see your "Node Weights and Weighted Interleave", this is an
interesting topic, we need some easy and efficient way to use tiered
memory.
Matthew last pointed out:
"probably the right way to do this is to make k = folio->flags, and then
just change a few places rather than changing all the places that test
'k'."
https://lore.kernel.org/linux-mm/ZUDFSEvpxxoGWmdG@xxxxxxxxxxxxxxxxxxxx/
I took a quick look, and the only thing I'm not confident about is that
some flags are stored in the head page, and some are stored on the
second page.
/* Which page is the flag stored in */
#define FOLIO_PF_ANY 0
#define FOLIO_PF_HEAD 0
#define FOLIO_PF_ONLY_HEAD 0
#define FOLIO_PF_NO_TAIL 0
#define FOLIO_PF_NO_COMPOUND 0
#define FOLIO_PF_SECOND 1
There's only a handful, so yeah the best way is probably to go ahead and
swap k = page->flags for k = *folio_flags(folio, 0) and then handle the
couple of outliars.
If you don't mind, I maybe try to convert it in my changes.
Thanks.
~Gregory
