6.15-stable review patch. If anyone has any objections, please let me know.
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From: Baolin Wang baolin.wang@linux.alibaba.com
commit 8d58d65621118fdca3ed6a0b3d658ba7e0e5153c upstream.
After commit acd7ccb284b8 ("mm: shmem: add large folio support for tmpfs"), we extend the 'huge=' option to allow any sized large folios for tmpfs, which means tmpfs will allow getting a highest order hint based on the size of write() and fallocate() paths, and then will try each allowable large order.
However, when the i915 driver allocates shmem memory, it doesn't provide hint information about the size of the large folio to be allocated, resulting in the inability to allocate PMD-sized shmem, which in turn affects GPU performance.
Patryk added:
: In my tests, the performance drop ranges from a few percent up to 13% : in Unigine Superposition under heavy memory usage on the CPU Core Ultra : 155H with the Xe 128 EU GPU. Other users have reported performance : impact up to 30% on certain workloads. Please find more in the : regressions reports: : https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/14645 : https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/13845 : : I believe the change should be backported to all active kernel branches : after version 6.12.
To fix this issue, we can use the inode's size as a write size hint in shmem_read_folio_gfp() to help allocate PMD-sized large folios.
Link: https://lkml.kernel.org/r/f7e64e99a3a87a8144cc6b2f1dddf7a89c12ce44.175392660... Fixes: acd7ccb284b8 ("mm: shmem: add large folio support for tmpfs") Signed-off-by: Baolin Wang baolin.wang@linux.alibaba.com Reported-by: Patryk Kowalczyk patryk@kowalczyk.ws Reported-by: Ville Syrjälä ville.syrjala@linux.intel.com Tested-by: Patryk Kowalczyk patryk@kowalczyk.ws Suggested-by: Hugh Dickins hughd@google.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/shmem.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/mm/shmem.c +++ b/mm/shmem.c @@ -5930,8 +5930,8 @@ struct folio *shmem_read_folio_gfp(struc struct folio *folio; int error;
- error = shmem_get_folio_gfp(inode, index, 0, &folio, SGP_CACHE, - gfp, NULL, NULL); + error = shmem_get_folio_gfp(inode, index, i_size_read(inode), + &folio, SGP_CACHE, gfp, NULL, NULL); if (error) return ERR_PTR(error);