On 17.09.25 20:51, Kyle Meyer wrote:
On Wed, Sep 17, 2025 at 09:02:55AM +0200, David Hildenbrand wrote:
+
+ 0 - Enable soft offline
+ 1 - Disable soft offline for HugeTLB pages
+
+Supported values::
+
+ 0 - Soft offline is disabled
+ 1 - Soft offline is enabled
+ 3 - Soft offline is enabled (disabled for HugeTLB pages)
This looks very adhoc even though existing behavior is preserved.
- Are HugeTLB pages the only page types to be considered ?
- How the remaining bits here are going to be used later ?
What I proposed (that could be better documented here) is that all other
bits except the first one will be a disable mask when bit 0 is set.
2 - ... but yet disabled for hugetlb
4 - ... but yet disabled for $WHATEVER
8 - ... but yet disabled for $WHATEVERELSE
Also without a bit-wise usage roadmap, is not changing a procfs
interface (ABI) bit problematic ?
For now we failed setting it to values that are neither 0 or 1, IIUC
set_enable_soft_offline() correctly?
Yes, -EINVAL will be returned.
So there should not be any problem, or which scenario do you have in mind?
Here's an alternative approach.
Do not modify the existing sysctl parameter:
/proc/sys/vm/enable_soft_offline
0 - Soft offline is disabled
1 - Soft offline is enabled
Instead, introduce a new sysctl parameter:
/proc/sys/vm/enable_soft_offline_hugetlb
0 - Soft offline is disabled for HugeTLB pages
1 - Soft offline is enabled for HugeTLB pages
and note in documentation that this setting only takes effect if
enable_soft_offline is enabled.
Anshuman (and David), would you prefer this?
Hmm, at least I don't particularly like that. For each new exception we
would create a new file, and the file has weird semantics such that it
has no meaning when enable_soft_offline=0.
--
Cheers
David / dhildenb
