On Wed, Feb 21, 2024 at 05:27:54PM +0800, Baolin Wang wrote:
Based on the analysis of the various scenarios above, determine whether fallback is
permitted according to the migration reason in alloc_hugetlb_folio_nodemask().
Hi Baolin,
The high level reasoning makes sense to me, taking a step back and
thinking about all cases and possible outcomes makes sense to me.
I plan to look closer, but I something that caught my eye:
}
spin_unlock_irq(&hugetlb_lock);
+ if (gfp_mask & __GFP_THISNODE)
+ goto alloc_new;
+
+ /*
+ * Note: the memory offline, memory failure and migration syscalls can break
+ * the per-node hugetlb pool. Other cases can not allocate new hugetlb on
+ * other nodes.
+ */
+ switch (reason) {
+ case MR_MEMORY_HOTPLUG:
+ case MR_MEMORY_FAILURE:
+ case MR_SYSCALL:
+ case MR_MEMPOLICY_MBIND:
+ allowed_fallback = true;
+ break;
+ default:
+ break;
+ }
+
+ if (!allowed_fallback)
+ gfp_mask |= __GFP_THISNODE;
I think it would be better if instead of fiddling with gfp here,
have htlb_alloc_mask() have a second argument with the MR_reason,
do the switch there and enable GFP_THISNODE.
Then alloc_hugetlb_folio_nodemask() would already get the right mask. >
I think that that might be more clear as it gets encapsulated in the
function that directly gives us the gfp.
Does that makes sense?