On 2024/10/11 14:59, Kefeng Wang wrote:
The tmpfs could support large folio, but there is some configurable
options(mount options and runtime deny/force) to enable/disable large
folio allocation, so there is a performance issue when perform write
without large folio, the issue is similar to commit 4e527d5841e2
("iomap: fault in smaller chunks for non-large folio mappings").
Don't call mapping_set_large_folios() in __shmem_get_inode() when
large folio is disabled to fix it.
Fixes: 9aac777aaf94 ("filemap: Convert generic_perform_write() to support large folios")
Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
---
v3:
- don't enable large folio suppport in __shmem_get_inode() if disabled,
suggested by Matthew.
v2:
- Don't use IOCB flags
mm/shmem.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/mm/shmem.c b/mm/shmem.c
index 0a2f78c2b919..2b859ac4ddc5 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2850,7 +2850,10 @@ static struct inode *__shmem_get_inode(struct mnt_idmap *idmap,
cache_no_acl(inode);
if (sbinfo->noswap)
mapping_set_unevictable(inode->i_mapping);
- mapping_set_large_folios(inode->i_mapping);
+
+ if ((sbinfo->huge && shmem_huge != SHMEM_HUGE_DENY) ||
+ shmem_huge == SHMEM_HUGE_FORCE)
+ mapping_set_large_folios(inode->i_mapping);
IMHO, I'm still a little concerned about the 'shmem_huge' validation.
Since the 'shmem_huge' can be set at runtime, that means file mapping
with 'huge=always' option might miss the opportunity to allocate large
folios if the 'shmem_huge' is changed from 'deny' from 'always' at runtime.
So I'd like to drop the 'shmem_huge' validation and add some comments to
indicate 'deny' and 'force' options are only for testing purpose and
performence issue should not be a problem in the real production
environments.
That's just my 2 cents:)
