On 2024/10/9 22:28, David Hildenbrand wrote:
On 09.10.24 12:44, Ryan Roberts wrote:
On 09/10/2024 10:15, Kefeng Wang wrote:
On 2024/9/13 18:36, Kefeng Wang wrote:
Hi All,
On 2024/9/10 22:18, Kefeng Wang wrote:
On 2024/9/10 22:06, Kefeng Wang wrote:
When the hugepage parameter is true in vma_alloc_folio(), it
indicates
that we only try allocation on preferred node if possible for
PMD_ORDER,
Should remove "for PMD_ORDER", I mean that it was used for
PMD_ORDER, but for
other high-order, it will reduce the success rate of allocation if
without
ddc1a5cbc05d.
but it could lead to lots of failures for large folio allocation,
luckily the hugepage parameter was deprecated since commit
ddc1a5cbc05d
("mempolicy: alloc_pages_mpol() for NUMA policy without vma"), so no
effect on runtime behavior.
Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
---
Found the issue when backport mthp to inner kernel without
ddc1a5cbc05d,
but for mainline, there is no issue, no clue why hugepage
parameter was
retained, maybe just kill the parameter for mainline?
Any comments, fix in alloc_anon_folio() or remove hugepage parameter in
vma_alloc_folio(), thanks.
* vma_alloc_folio - Allocate a folio for a VMA.
@hugepage: Unused (was: For hugepages try only preferred node if
possible).
Since hugepage won't be used in vma_alloc_folio(), maybe just delete
this
parameter?
Sorry for the radio silence. Given the param is no longer used, I
think it would
be cleaner to just remove it.
Agreed, no dead code.
Sure.
It was set to true here on purpose though; the aim was to follow the
pattern set
by PMD-sized THP, which also sets it to true. And the aargument was
that the
benefit of having a huge page would be outstripped by having to access
it on a
remote node.>>
Now that the parameter is deprecated, do you know if the policy is still
enforced by other means?
Right, it might indicate a bug. So figuring out why there are no users
left would be interesting. Maybe it was all on purpose.
Before v6.7 ddc1a5cbc05d(mTHP from v6.8), it checks hugepage parameter
(only for PMD THP), after that commit, we check the order == PMD_ORDER,
so no different for PMD THP, but for other high-order, it doesn't follow
the pattern set by PMD THP.
if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
/* filter "hugepage" allocation, unless from alloc_pages() */
order == HPAGE_PMD_ORDER && ilx != NO_INTERLEAVE_INDEX) {
"The interleave index is almost always irrelevant unless MPOL_INTERLEAVE:
with one exception in alloc_pages_mpol(), where the NO_INTERLEAVE_INDEX
passed down from vma-less alloc_pages() is also used as hint not to use
THP-style hugepage allocation - to avoid the overhead of a hugepage arg
(though I don't understand why we never just added a GFP bit for THP - if
it actually needs a different allocation strategy from other pages of the
same order). vma_alloc_folio() still carries its hugepage arg here, but
it is not used, and should be removed when agreed.
"
For Hugh's changelog, it seems that we could just remove it, but since
no mTHP when made this change, Hugh didn't take into account for other
high-order folio allocation.
