Re: [PATCH 1/1] vhost scsi: allocate vhost_scsi with GFP_NOWAIT to avoid delay

[Jason Wang]

On 2021/1/21 13:03, Dongli Zhang wrote:
> The size of 'struct vhost_scsi' is order-10 (~2.3MB). It may take long time
> delay by kzalloc() to compact memory pages when there is a lack of
> high-order pages. As a result, there is latency to create a VM (with
> vhost-scsi) or to hotadd vhost-scsi-based storage.
>
> The prior commit 595cb754983d ("vhost/scsi: use vmalloc for order-10
> allocation") prefers to fallback only when really needed, while this patch
> changes allocation to GFP_NOWAIT in order to avoid the delay caused by
> memory page compact.
>
> Cc: Aruna Ramakrishna <aruna.ramakrishna@xxxxxxxxxx>
> Cc: Joe Jin <joe.jin@xxxxxxxxxx>
> Signed-off-by: Dongli Zhang <dongli.zhang@xxxxxxxxxx>
> ---
> Another option is to rework by reducing the size of 'struct vhost_scsi',
> e.g., by replacing inline vhost_scsi.vqs with just memory pointers while
> each vhost_scsi.vqs[i] should be allocated separately. Please let me
> know if that option is better.
>
>   drivers/vhost/scsi.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
> index 4ce9f00ae10e..85eaa4e883f4 100644
> --- a/drivers/vhost/scsi.c
> +++ b/drivers/vhost/scsi.c
> @@ -1814,7 +1814,7 @@ static int vhost_scsi_open(struct inode *inode, struct file *f)
>   	struct vhost_virtqueue **vqs;
>   	int r = -ENOMEM, i;
>   
> -	vs = kzalloc(sizeof(*vs), GFP_KERNEL | __GFP_NOWARN | __GFP_RETRY_MAYFAIL);
> +	vs = kzalloc(sizeof(*vs), GFP_NOWAIT | __GFP_NOWARN);
>   	if (!vs) {
>   		vs = vzalloc(sizeof(*vs));
>   		if (!vs)


Can we use kvzalloc?

Thanks