Vasily Averin <vvs@xxxxxxxxxxxxx> writes:
> Currently newly allocated swap_info_struct can be quickly freed.
> This patch avoid uneccessary high-order page allocation and helps
> to decrease the memory pressure.
I think swapon/swapoff are rare operations, so it will not increase the
memory pressure much.
Best Regards,
Huang, Ying
> Signed-off-by: Vasily Averin <vvs@xxxxxxxxxxxxx>
> ---
> mm/swapfile.c | 18 +++++++++++++-----
> 1 file changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 8688ae65ef58..53ec2f0cdf26 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -2809,14 +2809,17 @@ late_initcall(max_swapfiles_check);
>
> static struct swap_info_struct *alloc_swap_info(void)
> {
> - struct swap_info_struct *p;
> + struct swap_info_struct *p = NULL;
> unsigned int type;
> int i;
> + bool force_alloc = false;
>
> - p = kvzalloc(sizeof(*p), GFP_KERNEL);
> - if (!p)
> - return ERR_PTR(-ENOMEM);
> -
> +retry:
> + if (force_alloc) {
> + p = kvzalloc(sizeof(*p), GFP_KERNEL);
> + if (!p)
> + return ERR_PTR(-ENOMEM);
> + }
> spin_lock(&swap_lock);
> for (type = 0; type < nr_swapfiles; type++) {
> if (!(swap_info[type]->flags & SWP_USED))
> @@ -2828,6 +2831,11 @@ static struct swap_info_struct *alloc_swap_info(void)
> return ERR_PTR(-EPERM);
> }
> if (type >= nr_swapfiles) {
> + if (!force_alloc) {
> + force_alloc = true;
> + spin_unlock(&swap_lock);
> + goto retry;
> + }
> p->type = type;
> swap_info[type] = p;
> /*
