| Message ID | 20250214175709.76029-4-ryncsn@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm, swap: remove swap slot cache | expand |
On 02/15/25 at 01:57am, Kairui Song wrote: > From: Kairui Song <kasong@tencent.com> > > There are only two callers of __read_swap_cache_async not holding a swap > device reference, so make them hold a reference instead, and drop the > get/put_swap_device calls in __read_swap_cache_async. This should reduce > the overhead for swap in during page fault slightly. This looks good to me, while the log makes me take a little longer time to understand. Maybe rephrasing them a little bit can facilitate the log reading. Not sure if my understanding is correct. ======= Currently, __read_swap_cache_async() has get/put_swap_device() calls to increase/decrease a swap device reference. While some of its callers have held the swap device reference, e.g in do_swap_page() and shmem_swapin_folio() where __read_swap_cache_async() will finally called. Now there are only two excpetional callers not holding a swap device reference, so make them hold a reference instead. And drop the get/put_swap_device calls in __read_swap_cache_async. This should reduce the overhead for swap in during page fault slightly. ======== Other than the nit in log, this looks good to me. Reviewed-by: Baoquan He <bhe@redhat.com> > > Signed-off-by: Kairui Song <kasong@tencent.com> > --- > mm/swap_state.c | 14 ++++++++------ > mm/zswap.c | 6 ++++++ > 2 files changed, 14 insertions(+), 6 deletions(-) > > diff --git a/mm/swap_state.c b/mm/swap_state.c > index a54b035d6a6c..50840a2887a5 100644 > --- a/mm/swap_state.c > +++ b/mm/swap_state.c > @@ -426,17 +426,13 @@ struct folio *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, > struct mempolicy *mpol, pgoff_t ilx, bool *new_page_allocated, > bool skip_if_exists) > { > - struct swap_info_struct *si; > + struct swap_info_struct *si = swp_swap_info(entry); > struct folio *folio; > struct folio *new_folio = NULL; > struct folio *result = NULL; > void *shadow = NULL; > > *new_page_allocated = false; > - si = get_swap_device(entry); > - if (!si) > - return NULL; > - > for (;;) { > int err; > /* > @@ -532,7 +528,6 @@ struct folio *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, > put_swap_folio(new_folio, entry); > folio_unlock(new_folio); > put_and_return: > - put_swap_device(si); > if (!(*new_page_allocated) && new_folio) > folio_put(new_folio); > return result; > @@ -552,11 +547,16 @@ struct folio *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, > struct vm_area_struct *vma, unsigned long addr, > struct swap_iocb **plug) > { > + struct swap_info_struct *si; > bool page_allocated; > struct mempolicy *mpol; > pgoff_t ilx; > struct folio *folio; > > + si = get_swap_device(entry); > + if (!si) > + return NULL; > + > mpol = get_vma_policy(vma, addr, 0, &ilx); > folio = __read_swap_cache_async(entry, gfp_mask, mpol, ilx, > &page_allocated, false); > @@ -564,6 +564,8 @@ struct folio *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, > > if (page_allocated) > swap_read_folio(folio, plug); > + > + put_swap_device(si); > return folio; > } > > diff --git a/mm/zswap.c b/mm/zswap.c > index ac9d299e7d0c..83dfa1f9e689 100644 > --- a/mm/zswap.c > +++ b/mm/zswap.c > @@ -1051,14 +1051,20 @@ static int zswap_writeback_entry(struct zswap_entry *entry, > struct folio *folio; > struct mempolicy *mpol; > bool folio_was_allocated; > + struct swap_info_struct *si; > struct writeback_control wbc = { > .sync_mode = WB_SYNC_NONE, > }; > > /* try to allocate swap cache folio */ > + si = get_swap_device(swpentry); > + if (!si) > + return -EEXIST; > + > mpol = get_task_policy(current); > folio = __read_swap_cache_async(swpentry, GFP_KERNEL, mpol, > NO_INTERLEAVE_INDEX, &folio_was_allocated, true); > + put_swap_device(si); > if (!folio) > return -ENOMEM; > > -- > 2.48.1 >
diff --git a/mm/swap_state.c b/mm/swap_state.c index a54b035d6a6c..50840a2887a5 100644 --- a/mm/swap_state.c +++ b/mm/swap_state.c @@ -426,17 +426,13 @@ struct folio *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, struct mempolicy *mpol, pgoff_t ilx, bool *new_page_allocated, bool skip_if_exists) { - struct swap_info_struct *si; + struct swap_info_struct *si = swp_swap_info(entry); struct folio *folio; struct folio *new_folio = NULL; struct folio *result = NULL; void *shadow = NULL; *new_page_allocated = false; - si = get_swap_device(entry); - if (!si) - return NULL; - for (;;) { int err; /* @@ -532,7 +528,6 @@ struct folio *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, put_swap_folio(new_folio, entry); folio_unlock(new_folio); put_and_return: - put_swap_device(si); if (!(*new_page_allocated) && new_folio) folio_put(new_folio); return result; @@ -552,11 +547,16 @@ struct folio *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, struct vm_area_struct *vma, unsigned long addr, struct swap_iocb **plug) { + struct swap_info_struct *si; bool page_allocated; struct mempolicy *mpol; pgoff_t ilx; struct folio *folio; + si = get_swap_device(entry); + if (!si) + return NULL; + mpol = get_vma_policy(vma, addr, 0, &ilx); folio = __read_swap_cache_async(entry, gfp_mask, mpol, ilx, &page_allocated, false); @@ -564,6 +564,8 @@ struct folio *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, if (page_allocated) swap_read_folio(folio, plug); + + put_swap_device(si); return folio; } diff --git a/mm/zswap.c b/mm/zswap.c index ac9d299e7d0c..83dfa1f9e689 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -1051,14 +1051,20 @@ static int zswap_writeback_entry(struct zswap_entry *entry, struct folio *folio; struct mempolicy *mpol; bool folio_was_allocated; + struct swap_info_struct *si; struct writeback_control wbc = { .sync_mode = WB_SYNC_NONE, }; /* try to allocate swap cache folio */ + si = get_swap_device(swpentry); + if (!si) + return -EEXIST; + mpol = get_task_policy(current); folio = __read_swap_cache_async(swpentry, GFP_KERNEL, mpol, NO_INTERLEAVE_INDEX, &folio_was_allocated, true); + put_swap_device(si); if (!folio) return -ENOMEM;