linux-kernel - Re: [PATCH UPDATED2 3/3] vhost: apply cpumask and cgroup to vhost pollers

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Message-ID: <4C038D77.3060508@kernel.org>
Date:	Mon, 31 May 2010 12:20:39 +0200
From:	Tejun Heo <tj@...nel.org>
To:	Li Zefan <lizf@...fujitsu.com>
CC:	"Michael S. Tsirkin" <mst@...hat.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Sridhar Samudrala <sri@...ibm.com>,
	netdev <netdev@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dmitri Vorobiev <dmitri.vorobiev@...ial.com>,
	Jiri Kosina <jkosina@...e.cz>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH UPDATED2 3/3] vhost: apply cpumask and cgroup to vhost
 pollers

Apply the cpumask and cgroup of the initializing task to the created
vhost poller.

Based on Sridhar Samudrala's patch.  Li Zefan spotted a bug in error
path (twice), fixed (twice).

Cc: Michael S. Tsirkin <mst@...hat.com>
Cc: Sridhar Samudrala <samudrala.sridhar@...il.com>
Cc: Li Zefan <lizf@...fujitsu.com>
---
Heh... that's embarrassing.  Let's see if I can get it right the third
time.

Thank you.

 drivers/vhost/vhost.c |   36 ++++++++++++++++++++++++++++++++----
 1 file changed, 32 insertions(+), 4 deletions(-)

Index: work/drivers/vhost/vhost.c
===================================================================
--- work.orig/drivers/vhost/vhost.c
+++ work/drivers/vhost/vhost.c
@@ -23,6 +23,7 @@
 #include <linux/highmem.h>
 #include <linux/slab.h>
 #include <linux/kthread.h>
+#include <linux/cgroup.h>

 #include <linux/net.h>
 #include <linux/if_packet.h>
@@ -177,11 +178,29 @@ long vhost_dev_init(struct vhost_dev *de
 		    struct vhost_virtqueue *vqs, int nvqs)
 {
 	struct task_struct *poller;
-	int i;
+	cpumask_var_t mask;
+	int i, ret = -ENOMEM;
+
+	if (!alloc_cpumask_var(&mask, GFP_KERNEL))
+		goto out_free_mask;

 	poller = kthread_create(vhost_poller, dev, "vhost-%d", current->pid);
-	if (IS_ERR(poller))
-		return PTR_ERR(poller);
+	if (IS_ERR(poller)) {
+		ret = PTR_ERR(poller);
+		goto out_free_mask;
+	}
+
+	ret = sched_getaffinity(current->pid, mask);
+	if (ret)
+		goto out_stop_poller;
+
+	ret = sched_setaffinity(poller->pid, mask);
+	if (ret)
+		goto out_stop_poller;
+
+	ret = cgroup_attach_task_current_cg(poller);
+	if (ret)
+		goto out_stop_poller;

 	dev->vqs = vqs;
 	dev->nvqs = nvqs;
@@ -202,7 +221,16 @@ long vhost_dev_init(struct vhost_dev *de
 			vhost_poll_init(&dev->vqs[i].poll,
 					dev->vqs[i].handle_kick, POLLIN, dev);
 	}
-	return 0;
+
+	wake_up_process(poller);	/* avoid contributing to loadavg */
+	ret = 0;
+	goto out_free_mask;
+
+out_stop_poller:
+	kthread_stop(poller);
+out_free_mask:
+	free_cpumask_var(mask);
+	return ret;
 }

 /* Caller should have device mutex */
--
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