On Mon 05-11-18 14:17:01, Vasily Averin wrote:
> commit a2468cc9bfdf ("swap: choose swap device according to numa node")
> changed 'avail_lists' field of 'struct swap_info_struct' to an array.
> In popular linux distros it increased size of swap_info_struct up to
> 40 Kbytes and now swap_info_struct allocation requires order-4 page.
> Switch to kvzmalloc allows to avoid unexpected allocation failures.
While this fixes the most visible issue is this a good long term
solution? Aren't we wasting memory without a good reason? IIRC our limit
for swap files/devices is much smaller than potential NUMA nodes numbers
so we can safely expect that would be only few numa affine nodes. I am
not really familiar with the rework which has added numa node awareness
but I wouls assueme that we should either go with one global table with
a linked list of possible swap_info structure per numa node or use a
sparse array.
That being said I am not really objecting to this patch as it is simple
and backportable to older (stable kernels).
I would even dare to add
Fixes: a2468cc9bfdf ("swap: choose swap device according to numa node")
because not being able to add a swap space on a fragmented system looks
like a regression to me.
> Acked-by: Aaron Lu <aaron.lu@xxxxxxxxx>
> Signed-off-by: Vasily Averin <vvs@xxxxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> ---
> mm/swapfile.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 644f746e167a..8688ae65ef58 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -2813,7 +2813,7 @@ static struct swap_info_struct *alloc_swap_info(void)
> unsigned int type;
> int i;
>
> - p = kzalloc(sizeof(*p), GFP_KERNEL);
> + p = kvzalloc(sizeof(*p), GFP_KERNEL);
> if (!p)
> return ERR_PTR(-ENOMEM);
>
> @@ -2824,7 +2824,7 @@ static struct swap_info_struct *alloc_swap_info(void)
> }
> if (type >= MAX_SWAPFILES) {
> spin_unlock(&swap_lock);
> - kfree(p);
> + kvfree(p);
> return ERR_PTR(-EPERM);
> }
> if (type >= nr_swapfiles) {
> @@ -2838,7 +2838,7 @@ static struct swap_info_struct *alloc_swap_info(void)
> smp_wmb();
> nr_swapfiles++;
> } else {
> - kfree(p);
> + kvfree(p);
> p = swap_info[type];
> /*
> * Do not memset this entry: a racing procfs swap_next()
> --
> 2.17.1
--
Michal Hocko
SUSE Labs
