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Revision 6e474083f3daf3a3546737f5d7d502ad12eb257c authored by Wei Xu on 01 December 2017, 10:10:36 UTC, committed by David S. Miller on 03 December 2017, 02:31:03 UTC 
vhost: fix skb leak in handle_rx()
 
Matthew found a roughly 40% tcp throughput regression with commit
c67df11f(vhost_net: try batch dequing from skb array) as discussed
in the following thread:
https://www.mail-archive.com/netdev@vger.kernel.org/msg187936.html

Eventually we figured out that it was a skb leak in handle_rx()
when sending packets to the VM. This usually happens when a guest
can not drain out vq as fast as vhost fills in, afterwards it sets
off the traffic jam and leaks skb(s) which occurs as no headcount
to send on the vq from vhost side.

This can be avoided by making sure we have got enough headcount
before actually consuming a skb from the batched rx array while
transmitting, which is simply done by moving checking the zero
headcount a bit ahead.

Signed-off-by: Wei Xu <wexu@redhat.com>
Reported-by: Matthew Rosato <mjrosato@linux.vnet.ibm.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
1 parent fa935ca
Raw File
smsc911x.c 
/* Specification for the SMSC911x NIC
 *
 * Copyright (C) 2006 Matsushita Electric Industrial Co., Ltd.
 * All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/io.h>
#include <linux/ioport.h>
#include <linux/smsc911x.h>
#include <unit/smsc911x.h>

static struct smsc911x_platform_config smsc911x_config = {
	.irq_polarity	= SMSC911X_IRQ_POLARITY_ACTIVE_LOW,
	.irq_type	= SMSC911X_IRQ_TYPE_OPEN_DRAIN,
	.flags		= SMSC911X_USE_32BIT,
};

static struct resource smsc911x_resources[] = {
	[0] = {
		.start	= SMSC911X_BASE,
		.end	= SMSC911X_BASE_END,
		.flags	= IORESOURCE_MEM,
	},
	[1] = {
		.start	= SMSC911X_IRQ,
		.end	= SMSC911X_IRQ,
		.flags	= IORESOURCE_IRQ,
	},
};

static struct platform_device smsc911x_device = {
	.name		= "smsc911x",
	.id		= 0,
	.num_resources	= ARRAY_SIZE(smsc911x_resources),
	.resource	= smsc911x_resources,
	.dev		= {
		.platform_data = &smsc911x_config,
	}
};

/*
 * add platform devices
 */
static int __init unit_device_init(void)
{
	platform_device_register(&smsc911x_device);
	return 0;
}

device_initcall(unit_device_init);
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