Ryan Roberts <ryan.roberts@xxxxxxx> 于2024年4月11日周四 22:30写道: > > On 09/04/2024 09:26, Barry Song wrote: > > From: Chuanhua Han <hanchuanhua@xxxxxxxx> > > > > While swapping in a large folio, we need to free swaps related to the whole > > folio. To avoid frequently acquiring and releasing swap locks, it is better > > to introduce an API for batched free. > > > > Signed-off-by: Chuanhua Han <hanchuanhua@xxxxxxxx> > > Co-developed-by: Barry Song <v-songbaohua@xxxxxxxx> > > Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx> > > Couple of nits; feel free to ignore. > > Reviewed-by: Ryan Roberts <ryan.roberts@xxxxxxx> > > > --- > > include/linux/swap.h | 5 +++++ > > mm/swapfile.c | 51 ++++++++++++++++++++++++++++++++++++++++++++ > > 2 files changed, 56 insertions(+) > > > > diff --git a/include/linux/swap.h b/include/linux/swap.h > > index 11c53692f65f..b7a107e983b8 100644 > > --- a/include/linux/swap.h > > +++ b/include/linux/swap.h > > @@ -483,6 +483,7 @@ extern void swap_shmem_alloc(swp_entry_t); > > extern int swap_duplicate(swp_entry_t); > > extern int swapcache_prepare(swp_entry_t); > > extern void swap_free(swp_entry_t); > > +extern void swap_free_nr(swp_entry_t entry, int nr_pages); > > extern void swapcache_free_entries(swp_entry_t *entries, int n); > > extern void free_swap_and_cache_nr(swp_entry_t entry, int nr); > > int swap_type_of(dev_t device, sector_t offset); > > @@ -564,6 +565,10 @@ static inline void swap_free(swp_entry_t swp) > > { > > } > > > > +void swap_free_nr(swp_entry_t entry, int nr_pages) > > +{ > > +} > > + > > static inline void put_swap_folio(struct folio *folio, swp_entry_t swp) > > { > > } > > diff --git a/mm/swapfile.c b/mm/swapfile.c > > index 28642c188c93..f4c65aeb088d 100644 > > --- a/mm/swapfile.c > > +++ b/mm/swapfile.c > > @@ -1356,6 +1356,57 @@ void swap_free(swp_entry_t entry) > > __swap_entry_free(p, entry); > > } > > > > +/* > > + * Free up the maximum number of swap entries at once to limit the > > + * maximum kernel stack usage. > > + */ > > +#define SWAP_BATCH_NR (SWAPFILE_CLUSTER > 512 ? 512 : SWAPFILE_CLUSTER) > > + > > +/* > > + * Called after swapping in a large folio, batched free swap entries > > + * for this large folio, entry should be for the first subpage and > > + * its offset is aligned with nr_pages > > + */ > > +void swap_free_nr(swp_entry_t entry, int nr_pages) > > +{ > > + int i, j; > > + struct swap_cluster_info *ci; > > + struct swap_info_struct *p; > > + unsigned int type = swp_type(entry); > > + unsigned long offset = swp_offset(entry); > > + int batch_nr, remain_nr; > > + DECLARE_BITMAP(usage, SWAP_BATCH_NR) = { 0 }; > > + > > + /* all swap entries are within a cluster for mTHP */ > > + VM_BUG_ON(offset % SWAPFILE_CLUSTER + nr_pages > SWAPFILE_CLUSTER); > > + > > + if (nr_pages == 1) { > > + swap_free(entry); > > + return; > > + } > > + > > + remain_nr = nr_pages; > > + p = _swap_info_get(entry); > > + if (p) { > > nit: perhaps return early if (!p) ? Then you dedent the for() block. Agreed! > > > + for (i = 0; i < nr_pages; i += batch_nr) { > > + batch_nr = min_t(int, SWAP_BATCH_NR, remain_nr); > > + > > + ci = lock_cluster_or_swap_info(p, offset); > > + for (j = 0; j < batch_nr; j++) { > > + if (__swap_entry_free_locked(p, offset + i * SWAP_BATCH_NR + j, 1)) > > + __bitmap_set(usage, j, 1); > > + } > > + unlock_cluster_or_swap_info(p, ci); > > + > > + for_each_clear_bit(j, usage, batch_nr) > > + free_swap_slot(swp_entry(type, offset + i * SWAP_BATCH_NR + j)); > > + > > nit: perhaps change to for (;;), and do the checks here to avoid clearing the > bitmap on the last run: > > i += batch_nr; > if (i < nr_pages) > break; Great, thank you for your advice! > > > + bitmap_clear(usage, 0, SWAP_BATCH_NR); > > + remain_nr -= batch_nr; > > + } > > + } > > +} > > + > > /* > > * Called after dropping swapcache to decrease refcnt to swap entries. > > */ > > -- Thanks, Chuanhua