linux-kernel - Re: [PATCH] vhost/scsi: use vmalloc for order-10 allocation

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Message-ID: <52389C0D.7070307@cogentembedded.com>
Date:	Tue, 17 Sep 2013 22:14:37 +0400
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
CC:	linux-kernel@...r.kernel.org, Dan Aloni <alonid@...atoscale.com>,
	kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
	netdev@...r.kernel.org, nab@...ux-iscsi.org,
	Asias He <asias@...hat.com>
Subject: Re: [PATCH] vhost/scsi: use vmalloc for order-10 allocation

Hello.

On 09/17/2013 11:21 AM, Michael S. Tsirkin wrote:

> As vhost scsi device struct is large, if the device is
> created on a busy system, kzalloc() might fail, so this patch does a
> fallback to vzalloc().

> As vmalloc() adds overhead on data-path, add __GFP_REPEAT
> to kzalloc() flags to do this fallback only when really needed.

> Reported-by: Dan Aloni <alonid@...atoscale.com>
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> ---

> I put this on my vhost fixes branch, intend to merge for 3.12.
> Dan, could you please confirm this works for you?

>   drivers/vhost/scsi.c | 41 +++++++++++++++++++++++++++--------------
>   1 file changed, 27 insertions(+), 14 deletions(-)

> diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
> index 4b79a1f..2c30bb0 100644
> --- a/drivers/vhost/scsi.c
> +++ b/drivers/vhost/scsi.c
> @@ -1373,21 +1373,30 @@ static int vhost_scsi_set_features(struct vhost_scsi *vs, u64 features)
>   	return 0;
>   }
>
> +static void vhost_scsi_free(struct vhost_scsi *vs)
> +{
> +        if (is_vmalloc_addr(vs))
> +                vfree(vs);
> +        else
> +                kfree(vs);

    Indent with the tabs ISO spaces, please.

> +}
> +
>   static int vhost_scsi_open(struct inode *inode, struct file *f)
>   {
>   	struct vhost_scsi *vs;
>   	struct vhost_virtqueue **vqs;
> -	int r, i;
> +	int r = -ENOMEM, i;
>
> -	vs = kzalloc(sizeof(*vs), GFP_KERNEL);
> -	if (!vs)
> -		return -ENOMEM;
> +        vs = kzalloc(sizeof(*vs), GFP_KERNEL | __GFP_NOWARN | __GFP_REPEAT);

    Indent here with a tab, please.

> +	if (!vs) {
> +		vs = vzalloc(sizeof(*vs));
> +		if (!vs)
> +			goto err_vs;
> +	}

WBR, Sergei

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