Kairui Song <[email protected]> writes: > On Fri, Jun 12, 2026 at 11:39:15PM +0800, Ritesh Harjani (IBM) wrote: >> On PowerPC Book3S64, MMU is selected at runtime, so macros like >> PMD_SHIFT are effectively runtime variables in the Book3S64 code. THP >> swap code uses these macros to size some of its array data structures >> based on PMD_ORDER e.g. SWAPFILE_CLUSTER macro is used for this very >> purpose. >> Hence this patch initializes SWAPFILE_CLUSTER at runtime and also >> modifies swap_table and swap_memcg_table which were earlier using this >> macro for defining the number of table entries. >> >> Signed-off-by: Ritesh Harjani (IBM) <[email protected]> >> --- >> mm/swap.h | 5 +++-- >> mm/swap_table.h | 6 ++---- >> mm/swapfile.c | 27 ++++++++++++++++++++++----- >> 3 files changed, 27 insertions(+), 11 deletions(-) > > Hi Ritesh, > > Thanks for the patch. >
Thanks Kairui for taking a look at this. Sorry about the delayed response, (was on travel to #OSSMumbai). >> >> diff --git a/mm/swap.h b/mm/swap.h >> index 77d2d14eda42..956879a69ddd 100644 >> --- a/mm/swap.h >> +++ b/mm/swap.h >> @@ -26,11 +26,12 @@ extern int page_cluster; >> #define SWAP_TABLE_HAS_ZEROFLAG ((BITS_PER_LONG - >> SWAP_CACHE_PFN_MARK_BITS - \ >> SWAP_CACHE_PFN_BITS) > >> SWAP_COUNT_MIN_BITS) >> >> +extern unsigned int swap_slots_in_cluster __read_mostly; > > Maybe __ro_after_init is better for this kind of use case? > yup. I can change that. >> +#define SWAPFILE_CLUSTER swap_slots_in_cluster >> + >> #ifdef CONFIG_THP_SWAP >> -#define SWAPFILE_CLUSTER HPAGE_PMD_NR > > So on Book3S64, HPAGE_PMD_NR is also a variable right? Then we don't really > need to change the SWAPFILE_CLUSTER defination here? We just need to adjust > the users of this macro so the build will pass? > Right. Earlier I was playing with different values of this via an arch_xxx variant. But for book3s64 usecase, the default values are fine. So, I agree, we need not change SWAPFILE_CLUSTER here. I can update the patch with the suggested changes in v4. -ritesh
