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

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Date:	Tue, 17 Sep 2013 22:51:54 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Sergei Shtylyov <sergei.shtylyov@...entembedded.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

On Tue, Sep 17, 2013 at 10:14:37PM +0400, Sergei Shtylyov wrote:
> 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

Thanks, I'll fix this up.
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