On 3/8/21 3:28 AM, Miaohe Lin wrote:
> The fault_mutex hashing overhead can be avoided in truncate_op case because
> page faults can not race with truncation in this routine. So calculate hash
> for fault_mutex only in !truncate_op case to save some cpu cycles.
>
> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> ---
> fs/hugetlbfs/inode.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index c262566f7c5d..d81f52b87bd7 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -482,10 +482,9 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
>
> for (i = 0; i < pagevec_count(&pvec); ++i) {
> struct page *page = pvec.pages[i];
> - u32 hash;
> + u32 hash = 0;
Do we need to initialize hash here?
I would not bring this up normally, but the purpose of the patch is to save
cpu cycles.
--
Mike Kravetz
>
> index = page->index;
> - hash = hugetlb_fault_mutex_hash(mapping, index);
> if (!truncate_op) {
> /*
> * Only need to hold the fault mutex in the
> @@ -493,6 +492,7 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
> * page faults. Races are not possible in the
> * case of truncation.
> */
> + hash = hugetlb_fault_mutex_hash(mapping, index);
> mutex_lock(&hugetlb_fault_mutex_table[hash]);
> }
>
>
