github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-05-28 00:53:34 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

mm/shmem: use xas_try_split() in shmem_split_large_entry()

Browse Source 
During shmem_split_large_entry(), large swap entries are covering n slots
and an order-0 folio needs to be inserted.

Instead of splitting all n slots, only the 1 slot covered by the folio
need to be split and the remaining n-1 shadow entries can be retained with
orders ranging from 0 to n-1.  This method only requires
(n/XA_CHUNK_SHIFT) new xa_nodes instead of (n % XA_CHUNK_SHIFT) *
(n/XA_CHUNK_SHIFT) new xa_nodes, compared to the original
xas_split_alloc() + xas_split() one.

For example, to split an order-9 large swap entry (assuming XA_CHUNK_SHIFT
is 6), 1 xa_node is needed instead of 8.

xas_try_split_min_order() is used to reduce the number of calls to
xas_try_split() during split.

Link: https://lkml.kernel.org/r/20250314222113.711703-3-ziy@nvidia.com
Signed-off-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Tested-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kairui Song <kasong@tencent.com>
Cc: Mattew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Kirill A. Shuemov <kirill.shutemov@linux.intel.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Yang Shi <yang@os.amperecomputing.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Zi Yan 2025-03-14 18:21:13 -04:00 committed by Andrew Morton
parent 200a89c159
commit d53c78fffe
1 changed files with 28 additions and 31 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

59
mm/shmem.c
View File

@ -2153,15 +2153,16 @@ static int shmem_split_large_entry(struct inode *inode, pgoff_t index,
{
struct address_space *mapping = inode->i_mapping;
XA_STATE_ORDER(xas, &mapping->i_pages, index, 0);
void *alloced_shadow = NULL;
int alloced_order = 0, i;
int split_order = 0, entry_order;
int i;
/* Convert user data gfp flags to xarray node gfp flags */
gfp &= GFP_RECLAIM_MASK;
for (;;) {
int order = -1, split_order = 0;
void *old = NULL;
int cur_order;
pgoff_t swap_index;
xas_lock_irq(&xas);
old = xas_load(&xas);
@ -2170,60 +2171,56 @@ static int shmem_split_large_entry(struct inode *inode, pgoff_t index,
goto unlock;
}
order = xas_get_order(&xas);
entry_order = xas_get_order(&xas);
/* Swap entry may have changed before we re-acquire the lock */
if (alloced_order &&
(old != alloced_shadow || order != alloced_order)) {
xas_destroy(&xas);
alloced_order = 0;
}
if (!entry_order)
goto unlock;
/* Try to split large swap entry in pagecache */
if (order > 0) {
if (!alloced_order) {
split_order = order;
cur_order = entry_order;
swap_index = round_down(index, 1 << entry_order);
split_order = xas_try_split_min_order(cur_order);
while (cur_order > 0) {
pgoff_t aligned_index =
round_down(index, 1 << cur_order);
pgoff_t swap_offset = aligned_index - swap_index;
xas_set_order(&xas, index, split_order);
xas_try_split(&xas, old, cur_order);
if (xas_error(&xas))
goto unlock;
}
xas_split(&xas, old, order);
/*
* Re-set the swap entry after splitting, and the swap
* offset of the original large entry must be continuous.
*/
for (i = 0; i < 1 << order; i++) {
pgoff_t aligned_index = round_down(index, 1 << order);
for (i = 0; i < 1 << cur_order;
i += (1 << split_order)) {
swp_entry_t tmp;
tmp = swp_entry(swp_type(swap), swp_offset(swap) + i);
tmp = swp_entry(swp_type(swap),
swp_offset(swap) + swap_offset +
i);
__xa_store(&mapping->i_pages, aligned_index + i,
swp_to_radix_entry(tmp), 0);
}
cur_order = split_order;
split_order = xas_try_split_min_order(split_order);
}
unlock:
xas_unlock_irq(&xas);
/* split needed, alloc here and retry. */
if (split_order) {
xas_split_alloc(&xas, old, split_order, gfp);
if (xas_error(&xas))
goto error;
alloced_shadow = old;
alloced_order = split_order;
xas_reset(&xas);
continue;
}
if (!xas_nomem(&xas, gfp))
break;
}
error:
if (xas_error(&xas))
return xas_error(&xas);
return alloced_order;
return entry_order;
}
/*