On Sat, 3 Aug 2024 00:20:31 +1200 Barry Song <21cnbao@xxxxxxxxx> wrote:
> From: Chuanhua Han <hanchuanhua@xxxxxxxx>
>
> Currently, we have mTHP features, but unfortunately, without support for large
> folio swap-ins, once these large folios are swapped out, they are lost because
> mTHP swap is a one-way process. The lack of mTHP swap-in functionality prevents
> mTHP from being used on devices like Android that heavily rely on swap.
>
> This patch introduces mTHP swap-in support. It starts from sync devices such
> as zRAM. This is probably the simplest and most common use case, benefiting
> billions of Android phones and similar devices with minimal implementation
> cost. In this straightforward scenario, large folios are always exclusive,
> eliminating the need to handle complex rmap and swapcache issues.
>
> It offers several benefits:
> 1. Enables bidirectional mTHP swapping, allowing retrieval of mTHP after
> swap-out and swap-in. Large folios in the buddy system are also
> preserved as much as possible, rather than being fragmented due
> to swap-in.
>
> 2. Eliminates fragmentation in swap slots and supports successful
> THP_SWPOUT.
>
> w/o this patch (Refer to the data from Chris's and Kairui's latest
> swap allocator optimization while running ./thp_swap_allocator_test
> w/o "-a" option [1]):
>
> ...
>
> +static struct folio *alloc_swap_folio(struct vm_fault *vmf)
> +{
> + struct vm_area_struct *vma = vmf->vma;
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
>
> ...
>
> +#endif
> + return vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, vma, vmf->address, false);
> +}
Generates an unused-variable warning with allnoconfig. Because
vma_alloc_folio_noprof() was implemented as a macro instead of an
inlined C function. Why do we keep doing this.
Please check:
From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Subject: mm-support-large-folios-swap-in-for-zram-like-devices-fix
Date: Sat Aug 3 11:59:00 AM PDT 2024
fix unused var warning
mm/memory.c: In function 'alloc_swap_folio':
mm/memory.c:4062:32: warning: unused variable 'vma' [-Wunused-variable]
4062 | struct vm_area_struct *vma = vmf->vma;
| ^~~
Cc: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Cc: Barry Song <v-songbaohua@xxxxxxxx>
Cc: Chris Li <chrisl@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Chuanhua Han <hanchuanhua@xxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Gao Xiang <xiang@xxxxxxxxxx>
Cc: "Huang, Ying" <ying.huang@xxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Kairui Song <kasong@xxxxxxxxxxx>
Cc: Kalesh Singh <kaleshsingh@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Nhat Pham <nphamcs@xxxxxxxxx>
Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
Cc: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Cc: Shakeel Butt <shakeel.butt@xxxxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Cc: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
--- a/mm/memory.c~mm-support-large-folios-swap-in-for-zram-like-devices-fix
+++ a/mm/memory.c
@@ -4059,8 +4059,8 @@ static inline bool can_swapin_thp(struct
static struct folio *alloc_swap_folio(struct vm_fault *vmf)
{
- struct vm_area_struct *vma = vmf->vma;
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+ struct vm_area_struct *vma = vmf->vma;
unsigned long orders;
struct folio *folio;
unsigned long addr;
@@ -4128,7 +4128,8 @@ static struct folio *alloc_swap_folio(st
fallback:
#endif
- return vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, vma, vmf->address, false);
+ return vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, vmf->vma,
+ vmf->address, false);
}
_
