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
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
lis3lv02d_spi.c
/*
 * lis3lv02d_spi - SPI glue layer for lis3lv02d
 *
 * Copyright (c) 2009 Daniel Mack <daniel@caiaq.de>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2 as
 *  publishhed by the Free Software Foundation.
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/err.h>
#include <linux/input.h>
#include <linux/interrupt.h>
#include <linux/workqueue.h>
#include <linux/spi/spi.h>
#include <linux/pm.h>
#include <linux/of.h>
#include <linux/of_platform.h>
#include <linux/of_device.h>

#include "lis3lv02d.h"

#define DRV_NAME 	"lis3lv02d_spi"
#define LIS3_SPI_READ	0x80

static int lis3_spi_read(struct lis3lv02d *lis3, int reg, u8 *v)
{
	struct spi_device *spi = lis3->bus_priv;
	int ret = spi_w8r8(spi, reg | LIS3_SPI_READ);
	if (ret < 0)
		return -EINVAL;

	*v = (u8) ret;
	return 0;
}

static int lis3_spi_write(struct lis3lv02d *lis3, int reg, u8 val)
{
	u8 tmp[2] = { reg, val };
	struct spi_device *spi = lis3->bus_priv;
	return spi_write(spi, tmp, sizeof(tmp));
}

static int lis3_spi_init(struct lis3lv02d *lis3)
{
	u8 reg;
	int ret;

	/* power up the device */
	ret = lis3->read(lis3, CTRL_REG1, &reg);
	if (ret < 0)
		return ret;

	reg |= CTRL1_PD0 | CTRL1_Xen | CTRL1_Yen | CTRL1_Zen;
	return lis3->write(lis3, CTRL_REG1, reg);
}

static union axis_conversion lis3lv02d_axis_normal =
	{ .as_array = { 1, 2, 3 } };

#ifdef CONFIG_OF
static const struct of_device_id lis302dl_spi_dt_ids[] = {
	{ .compatible = "st,lis302dl-spi" },
	{}
};
MODULE_DEVICE_TABLE(of, lis302dl_spi_dt_ids);
#endif

static int lis302dl_spi_probe(struct spi_device *spi)
{
	int ret;

	spi->bits_per_word = 8;
	spi->mode = SPI_MODE_0;
	ret = spi_setup(spi);
	if (ret < 0)
		return ret;

	lis3_dev.bus_priv	= spi;
	lis3_dev.init		= lis3_spi_init;
	lis3_dev.read		= lis3_spi_read;
	lis3_dev.write		= lis3_spi_write;
	lis3_dev.irq		= spi->irq;
	lis3_dev.ac		= lis3lv02d_axis_normal;
	lis3_dev.pdata		= spi->dev.platform_data;

#ifdef CONFIG_OF
	if (of_match_device(lis302dl_spi_dt_ids, &spi->dev)) {
		lis3_dev.of_node = spi->dev.of_node;
		ret = lis3lv02d_init_dt(&lis3_dev);
		if (ret)
			return ret;
	}
#endif
	spi_set_drvdata(spi, &lis3_dev);

	return lis3lv02d_init_device(&lis3_dev);
}

static int lis302dl_spi_remove(struct spi_device *spi)
{
	struct lis3lv02d *lis3 = spi_get_drvdata(spi);
	lis3lv02d_joystick_disable(lis3);
	lis3lv02d_poweroff(lis3);

	return lis3lv02d_remove_fs(&lis3_dev);
}

#ifdef CONFIG_PM_SLEEP
static int lis3lv02d_spi_suspend(struct device *dev)
{
	struct spi_device *spi = to_spi_device(dev);
	struct lis3lv02d *lis3 = spi_get_drvdata(spi);

	if (!lis3->pdata || !lis3->pdata->wakeup_flags)
		lis3lv02d_poweroff(&lis3_dev);

	return 0;
}

static int lis3lv02d_spi_resume(struct device *dev)
{
	struct spi_device *spi = to_spi_device(dev);
	struct lis3lv02d *lis3 = spi_get_drvdata(spi);

	if (!lis3->pdata || !lis3->pdata->wakeup_flags)
		lis3lv02d_poweron(lis3);

	return 0;
}
#endif

static SIMPLE_DEV_PM_OPS(lis3lv02d_spi_pm, lis3lv02d_spi_suspend,
			 lis3lv02d_spi_resume);

static struct spi_driver lis302dl_spi_driver = {
	.driver	 = {
		.name   = DRV_NAME,
		.pm	= &lis3lv02d_spi_pm,
		.of_match_table = of_match_ptr(lis302dl_spi_dt_ids),
	},
	.probe	= lis302dl_spi_probe,
	.remove	= lis302dl_spi_remove,
};

module_spi_driver(lis302dl_spi_driver);

MODULE_AUTHOR("Daniel Mack <daniel@caiaq.de>");
MODULE_DESCRIPTION("lis3lv02d SPI glue layer");
MODULE_LICENSE("GPL");
MODULE_ALIAS("spi:" DRV_NAME);
back to top