On 6/22/23 07:42, Ryan Roberts wrote:
With the ptep API sufficiently refactored, we can now introduce a new
"contpte" API layer, which transparently manages the PTE_CONT bit for
user mappings. Whenever it detects a set of PTEs that meet the
requirements for a contiguous range, the PTEs are re-painted with the
PTE_CONT bit.
This initial change provides a baseline that can be optimized in future
commits. That said, fold/unfold operations (which imply tlb
invalidation) are avoided where possible with a few tricks for
access/dirty bit management.
Write-enable and write-protect modifications are likely non-optimal and
likely incure a regression in fork() performance. This will be addressed
separately.
Signed-off-by: Ryan Roberts <ryan.roberts@xxxxxxx>
---
Hi Ryan!
While trying out the full series from your gitlab features/granule_perf/all
branch, I found it necessary to EXPORT a symbol in order to build this.
Please see below:
...
+
+pte_t contpte_ptep_get(pte_t *ptep, pte_t orig_pte)
+{
+ /*
+ * Gather access/dirty bits, which may be populated in any of the ptes
+ * of the contig range. We are guarranteed to be holding the PTL, so any
+ * contiguous range cannot be unfolded or otherwise modified under our
+ * feet.
+ */
+
+ pte_t pte;
+ int i;
+
+ ptep = contpte_align_down(ptep);
+
+ for (i = 0; i < CONT_PTES; i++, ptep++) {
+ pte = __ptep_get(ptep);
+
+ /*
+ * Deal with the partial contpte_ptep_get_and_clear_full() case,
+ * where some of the ptes in the range may be cleared but others
+ * are still to do. See contpte_ptep_get_and_clear_full().
+ */
+ if (pte_val(pte) == 0)
+ continue;
+
+ if (pte_dirty(pte))
+ orig_pte = pte_mkdirty(orig_pte);
+
+ if (pte_young(pte))
+ orig_pte = pte_mkyoung(orig_pte);
+ }
+
+ return orig_pte;
+}
Here we need something like this, in order to get it to build in all
possible configurations:
EXPORT_SYMBOL_GPL(contpte_ptep_get);
(and a corresponding "#include linux/export.h" at the top of the file).
Because, the static inline functions invoke this routine, above.
thanks,
--
John Hubbard
NVIDIA
