* Re: [PATCH] Revert "tmpfs: don't enable large folios if not supported"
2026-04-23 1:41 [PATCH] Revert "tmpfs: don't enable large folios if not supported" Baolin Wang
@ 2026-04-23 2:37 ` Zi Yan
2026-04-23 2:46 ` Kefeng Wang
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: Zi Yan @ 2026-04-23 2:37 UTC (permalink / raw)
To: Baolin Wang
Cc: akpm, hughd, willy, david, ljs, lance.yang, wangkefeng.wang,
linux-mm, linux-kernel
On 22 Apr 2026, at 21:41, Baolin Wang wrote:
> This reverts commit 5a90c155defa684f3a21f68c3f8e40c056e6114c.
>
> Currently, when shmem mounts are initialized, they only use 'sbinfo->huge' to
> determine whether the shmem mount supports large folios. However, for anonymous
> shmem, whether it supports large folios can be dynamically configured via sysfs
> interfaces, so setting or not setting mapping_set_large_folios() during initialization
> cannot accurately reflect whether anonymous shmem actually supports large folios,
> which has already caused some confusion[1].
>
> Moreover, for tmpfs mounts, relying on 'sbinfo->huge' cannot keep the mapping_set_large_folios()
> setting consistent across all mappings in the entire tmpfs mount. In other words,
> under the same tmpfs mount, after remount, we might end up with some mappings
> supporting large folios (calling mapping_set_large_folios()) while others don't.
>
> After some investigation, I found that the write performance regression addressed
> by commit 5a90c155defa has already been fixed by the following commit 665575cff098b
> ("filemap: move prefaulting out of hot write path"). See the following test data:
>
> Base:
> dd if=/dev/zero of=/mnt/tmpfs/test bs=400K count=10485 (3.2 GB/s)
> dd if=/dev/zero of=/mnt/tmpfs/test bs=800K count=5242 (3.2 GB/s)
> dd if=/dev/zero of=/mnt/tmpfs/test bs=1600K count=2621 (3.1 GB/s)
> dd if=/dev/zero of=/mnt/tmpfs/test bs=2200K count=1906 (3.0 GB/s )
> dd if=/dev/zero of=/mnt/tmpfs/test bs=3000K count=1398 (3.0 GB/s)
> dd if=/dev/zero of=/mnt/tmpfs/test bs=4500K count=932 (3.1 GB/s)
>
> Base + revert 5a90c155defa:
> dd if=/dev/zero of=/mnt/tmpfs/test bs=400K count=10485 (3.3 GB/s)
> dd if=/dev/zero of=/mnt/tmpfs/test bs=800K count=5242 (3.3 GB/s)
> dd if=/dev/zero of=/mnt/tmpfs/test bs=1600K count=2621 (3.2 GB/s)
> dd if=/dev/zero of=/mnt/tmpfs/test bs=2200K count=1906 (3.1 GB/s)
> dd if=/dev/zero of=/mnt/tmpfs/testbs=3000K count=1398 (3.0 GB/s)
> dd if=/dev/zero of=/mnt/tmpfs/test bs=4500K count=932 (3.1 GB/s)
>
> The data is basically consistent with minor fluctuation noise. So we can now
> safely revert commit 5a90c155defa to set mapping_set_large_folios() for all
> shmem mounts unconditionally.
>
> [1] https://lore.kernel.org/all/ec927492-4577-4192-8fad-85eb1bb43121@linux.alibaba.com/
> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
> ---
> Note: for more investigation and test data, see:
> https://lore.kernel.org/all/116df9f9-4db7-40d4-a4a4-30a87c0feffa@linux.alibaba.com/
> Thanks Kefeng for confirming the performance issue.
> ---
> mm/shmem.c | 5 +----
> 1 file changed, 1 insertion(+), 4 deletions(-)
>
Thank you for the investigation and explanation.
Acked-by: Zi Yan <ziy@nvidia.com>
Best Regards,
Yan, Zi
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] Revert "tmpfs: don't enable large folios if not supported"
2026-04-23 1:41 [PATCH] Revert "tmpfs: don't enable large folios if not supported" Baolin Wang
2026-04-23 2:37 ` Zi Yan
@ 2026-04-23 2:46 ` Kefeng Wang
2026-04-23 2:57 ` Lance Yang
2026-04-23 13:20 ` David Hildenbrand (Arm)
3 siblings, 0 replies; 5+ messages in thread
From: Kefeng Wang @ 2026-04-23 2:46 UTC (permalink / raw)
To: Baolin Wang, akpm, hughd
Cc: willy, ziy, david, ljs, lance.yang, linux-mm, linux-kernel
On 4/23/2026 9:41 AM, Baolin Wang wrote:
> This reverts commit 5a90c155defa684f3a21f68c3f8e40c056e6114c.
>
> Currently, when shmem mounts are initialized, they only use 'sbinfo->huge' to
> determine whether the shmem mount supports large folios. However, for anonymous
> shmem, whether it supports large folios can be dynamically configured via sysfs
> interfaces, so setting or not setting mapping_set_large_folios() during initialization
> cannot accurately reflect whether anonymous shmem actually supports large folios,
> which has already caused some confusion[1].
>
> Moreover, for tmpfs mounts, relying on 'sbinfo->huge' cannot keep the mapping_set_large_folios()
> setting consistent across all mappings in the entire tmpfs mount. In other words,
> under the same tmpfs mount, after remount, we might end up with some mappings
> supporting large folios (calling mapping_set_large_folios()) while others don't.
>
> After some investigation, I found that the write performance regression addressed
> by commit 5a90c155defa has already been fixed by the following commit 665575cff098b
> ("filemap: move prefaulting out of hot write path"). See the following test data:
>
> Base:
> dd if=/dev/zero of=/mnt/tmpfs/test bs=400K count=10485 (3.2 GB/s)
> dd if=/dev/zero of=/mnt/tmpfs/test bs=800K count=5242 (3.2 GB/s)
> dd if=/dev/zero of=/mnt/tmpfs/test bs=1600K count=2621 (3.1 GB/s)
> dd if=/dev/zero of=/mnt/tmpfs/test bs=2200K count=1906 (3.0 GB/s )
> dd if=/dev/zero of=/mnt/tmpfs/test bs=3000K count=1398 (3.0 GB/s)
> dd if=/dev/zero of=/mnt/tmpfs/test bs=4500K count=932 (3.1 GB/s)
>
> Base + revert 5a90c155defa:
> dd if=/dev/zero of=/mnt/tmpfs/test bs=400K count=10485 (3.3 GB/s)
> dd if=/dev/zero of=/mnt/tmpfs/test bs=800K count=5242 (3.3 GB/s)
> dd if=/dev/zero of=/mnt/tmpfs/test bs=1600K count=2621 (3.2 GB/s)
> dd if=/dev/zero of=/mnt/tmpfs/test bs=2200K count=1906 (3.1 GB/s)
> dd if=/dev/zero of=/mnt/tmpfs/testbs=3000K count=1398 (3.0 GB/s)
> dd if=/dev/zero of=/mnt/tmpfs/test bs=4500K count=932 (3.1 GB/s)
>
> The data is basically consistent with minor fluctuation noise. So we can now
> safely revert commit 5a90c155defa to set mapping_set_large_folios() for all
> shmem mounts unconditionally.
>
> [1] https://lore.kernel.org/all/ec927492-4577-4192-8fad-85eb1bb43121@linux.alibaba.com/
> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
> ---
> Note: for more investigation and test data, see:
> https://lore.kernel.org/all/116df9f9-4db7-40d4-a4a4-30a87c0feffa@linux.alibaba.com/
> Thanks Kefeng for confirming the performance issue.
LGTM， Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> ---
> mm/shmem.c | 5 +----
> 1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 4ecefe02881d..dafbea53b22d 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -3087,10 +3087,7 @@ static struct inode *__shmem_get_inode(struct mnt_idmap *idmap,
> cache_no_acl(inode);
> if (sbinfo->noswap)
> mapping_set_unevictable(inode->i_mapping);
> -
> - /* Don't consider 'deny' for emergencies and 'force' for testing */
> - if (sbinfo->huge)
> - mapping_set_large_folios(inode->i_mapping);
> + mapping_set_large_folios(inode->i_mapping);
>
> switch (mode & S_IFMT) {
> default:
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] Revert "tmpfs: don't enable large folios if not supported"
2026-04-23 1:41 [PATCH] Revert "tmpfs: don't enable large folios if not supported" Baolin Wang
2026-04-23 2:37 ` Zi Yan
2026-04-23 2:46 ` Kefeng Wang
@ 2026-04-23 2:57 ` Lance Yang
2026-04-23 13:20 ` David Hildenbrand (Arm)
3 siblings, 0 replies; 5+ messages in thread
From: Lance Yang @ 2026-04-23 2:57 UTC (permalink / raw)
To: baolin.wang
Cc: akpm, hughd, willy, ziy, david, ljs, lance.yang, wangkefeng.wang,
linux-mm, linux-kernel
On Thu, Apr 23, 2026 at 09:41:42AM +0800, Baolin Wang wrote:
>This reverts commit 5a90c155defa684f3a21f68c3f8e40c056e6114c.
>
>Currently, when shmem mounts are initialized, they only use 'sbinfo->huge' to
>determine whether the shmem mount supports large folios. However, for anonymous
>shmem, whether it supports large folios can be dynamically configured via sysfs
>interfaces, so setting or not setting mapping_set_large_folios() during initialization
>cannot accurately reflect whether anonymous shmem actually supports large folios,
>which has already caused some confusion[1].
>
>Moreover, for tmpfs mounts, relying on 'sbinfo->huge' cannot keep the mapping_set_large_folios()
>setting consistent across all mappings in the entire tmpfs mount. In other words,
>under the same tmpfs mount, after remount, we might end up with some mappings
>supporting large folios (calling mapping_set_large_folios()) while others don't.
>
>After some investigation, I found that the write performance regression addressed
>by commit 5a90c155defa has already been fixed by the following commit 665575cff098b
>("filemap: move prefaulting out of hot write path"). See the following test data:
>
>Base:
>dd if=/dev/zero of=/mnt/tmpfs/test bs=400K count=10485 (3.2 GB/s)
>dd if=/dev/zero of=/mnt/tmpfs/test bs=800K count=5242 (3.2 GB/s)
>dd if=/dev/zero of=/mnt/tmpfs/test bs=1600K count=2621 (3.1 GB/s)
>dd if=/dev/zero of=/mnt/tmpfs/test bs=2200K count=1906 (3.0 GB/s )
>dd if=/dev/zero of=/mnt/tmpfs/test bs=3000K count=1398 (3.0 GB/s)
>dd if=/dev/zero of=/mnt/tmpfs/test bs=4500K count=932 (3.1 GB/s)
>
>Base + revert 5a90c155defa:
>dd if=/dev/zero of=/mnt/tmpfs/test bs=400K count=10485 (3.3 GB/s)
>dd if=/dev/zero of=/mnt/tmpfs/test bs=800K count=5242 (3.3 GB/s)
>dd if=/dev/zero of=/mnt/tmpfs/test bs=1600K count=2621 (3.2 GB/s)
>dd if=/dev/zero of=/mnt/tmpfs/test bs=2200K count=1906 (3.1 GB/s)
>dd if=/dev/zero of=/mnt/tmpfs/testbs=3000K count=1398 (3.0 GB/s)
>dd if=/dev/zero of=/mnt/tmpfs/test bs=4500K count=932 (3.1 GB/s)
>
>The data is basically consistent with minor fluctuation noise. So we can now
>safely revert commit 5a90c155defa to set mapping_set_large_folios() for all
>shmem mounts unconditionally.
>
>[1] https://lore.kernel.org/all/ec927492-4577-4192-8fad-85eb1bb43121@linux.alibaba.com/
>Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
>---
>Note: for more investigation and test data, see:
>https://lore.kernel.org/all/116df9f9-4db7-40d4-a4a4-30a87c0feffa@linux.alibaba.com/
>Thanks Kefeng for confirming the performance issue.
>---
Thanks for tackling this!
Reviewed-by: Lance Yang <lance.yang@linux.dev>
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] Revert "tmpfs: don't enable large folios if not supported"
2026-04-23 1:41 [PATCH] Revert "tmpfs: don't enable large folios if not supported" Baolin Wang
` (2 preceding siblings ...)
2026-04-23 2:57 ` Lance Yang
@ 2026-04-23 13:20 ` David Hildenbrand (Arm)
3 siblings, 0 replies; 5+ messages in thread
From: David Hildenbrand (Arm) @ 2026-04-23 13:20 UTC (permalink / raw)
To: Baolin Wang, akpm, hughd
Cc: willy, ziy, ljs, lance.yang, wangkefeng.wang, linux-mm,
linux-kernel
On 4/23/26 03:41, Baolin Wang wrote:
> This reverts commit 5a90c155defa684f3a21f68c3f8e40c056e6114c.
>
> Currently, when shmem mounts are initialized, they only use 'sbinfo->huge' to
> determine whether the shmem mount supports large folios. However, for anonymous
> shmem, whether it supports large folios can be dynamically configured via sysfs
> interfaces, so setting or not setting mapping_set_large_folios() during initialization
> cannot accurately reflect whether anonymous shmem actually supports large folios,
> which has already caused some confusion[1].
>
> Moreover, for tmpfs mounts, relying on 'sbinfo->huge' cannot keep the mapping_set_large_folios()
> setting consistent across all mappings in the entire tmpfs mount. In other words,
> under the same tmpfs mount, after remount, we might end up with some mappings
> supporting large folios (calling mapping_set_large_folios()) while others don't.
>
> After some investigation, I found that the write performance regression addressed
> by commit 5a90c155defa has already been fixed by the following commit 665575cff098b
> ("filemap: move prefaulting out of hot write path"). See the following test data:
>
> Base:
> dd if=/dev/zero of=/mnt/tmpfs/test bs=400K count=10485 (3.2 GB/s)
> dd if=/dev/zero of=/mnt/tmpfs/test bs=800K count=5242 (3.2 GB/s)
> dd if=/dev/zero of=/mnt/tmpfs/test bs=1600K count=2621 (3.1 GB/s)
> dd if=/dev/zero of=/mnt/tmpfs/test bs=2200K count=1906 (3.0 GB/s )
> dd if=/dev/zero of=/mnt/tmpfs/test bs=3000K count=1398 (3.0 GB/s)
> dd if=/dev/zero of=/mnt/tmpfs/test bs=4500K count=932 (3.1 GB/s)
>
> Base + revert 5a90c155defa:
> dd if=/dev/zero of=/mnt/tmpfs/test bs=400K count=10485 (3.3 GB/s)
> dd if=/dev/zero of=/mnt/tmpfs/test bs=800K count=5242 (3.3 GB/s)
> dd if=/dev/zero of=/mnt/tmpfs/test bs=1600K count=2621 (3.2 GB/s)
> dd if=/dev/zero of=/mnt/tmpfs/test bs=2200K count=1906 (3.1 GB/s)
> dd if=/dev/zero of=/mnt/tmpfs/testbs=3000K count=1398 (3.0 GB/s)
> dd if=/dev/zero of=/mnt/tmpfs/test bs=4500K count=932 (3.1 GB/s)
>
> The data is basically consistent with minor fluctuation noise. So we can now
> safely revert commit 5a90c155defa to set mapping_set_large_folios() for all
> shmem mounts unconditionally.
>
> [1] https://lore.kernel.org/all/ec927492-4577-4192-8fad-85eb1bb43121@linux.alibaba.com/
> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
> ---
> Note: for more investigation and test data, see:
> https://lore.kernel.org/all/116df9f9-4db7-40d4-a4a4-30a87c0feffa@linux.alibaba.com/
Maybe add that as
Link: https://lore.kernel.org/all/116df9f9-4db7-40d4-a4a4-30a87c0feffa@linux.alibaba.com/
above?
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
--
Cheers,
David
^ permalink raw reply [flat|nested] 5+ messages in thread