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
omap_hwspinlock.c
/*
* OMAP hardware spinlock driver
*
* Copyright (C) 2010-2015 Texas Instruments Incorporated - http://www.ti.com
*
* Contact: Simon Que <sque@ti.com>
* Hari Kanigeri <h-kanigeri2@ti.com>
* Ohad Ben-Cohen <ohad@wizery.com>
*
* 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 published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/delay.h>
#include <linux/io.h>
#include <linux/bitops.h>
#include <linux/pm_runtime.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/hwspinlock.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include "hwspinlock_internal.h"
/* Spinlock register offsets */
#define SYSSTATUS_OFFSET 0x0014
#define LOCK_BASE_OFFSET 0x0800
#define SPINLOCK_NUMLOCKS_BIT_OFFSET (24)
/* Possible values of SPINLOCK_LOCK_REG */
#define SPINLOCK_NOTTAKEN (0) /* free */
#define SPINLOCK_TAKEN (1) /* locked */
static int omap_hwspinlock_trylock(struct hwspinlock *lock)
{
void __iomem *lock_addr = lock->priv;
/* attempt to acquire the lock by reading its value */
return (SPINLOCK_NOTTAKEN == readl(lock_addr));
}
static void omap_hwspinlock_unlock(struct hwspinlock *lock)
{
void __iomem *lock_addr = lock->priv;
/* release the lock by writing 0 to it */
writel(SPINLOCK_NOTTAKEN, lock_addr);
}
/*
* relax the OMAP interconnect while spinning on it.
*
* The specs recommended that the retry delay time will be
* just over half of the time that a requester would be
* expected to hold the lock.
*
* The number below is taken from an hardware specs example,
* obviously it is somewhat arbitrary.
*/
static void omap_hwspinlock_relax(struct hwspinlock *lock)
{
ndelay(50);
}
static const struct hwspinlock_ops omap_hwspinlock_ops = {
.trylock = omap_hwspinlock_trylock,
.unlock = omap_hwspinlock_unlock,
.relax = omap_hwspinlock_relax,
};
static int omap_hwspinlock_probe(struct platform_device *pdev)
{
struct device_node *node = pdev->dev.of_node;
struct hwspinlock_device *bank;
struct hwspinlock *hwlock;
struct resource *res;
void __iomem *io_base;
int num_locks, i, ret;
/* Only a single hwspinlock block device is supported */
int base_id = 0;
if (!node)
return -ENODEV;
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
if (!res)
return -ENODEV;
io_base = ioremap(res->start, resource_size(res));
if (!io_base)
return -ENOMEM;
/*
* make sure the module is enabled and clocked before reading
* the module SYSSTATUS register
*/
pm_runtime_enable(&pdev->dev);
ret = pm_runtime_get_sync(&pdev->dev);
if (ret < 0) {
pm_runtime_put_noidle(&pdev->dev);
goto iounmap_base;
}
/* Determine number of locks */
i = readl(io_base + SYSSTATUS_OFFSET);
i >>= SPINLOCK_NUMLOCKS_BIT_OFFSET;
/*
* runtime PM will make sure the clock of this module is
* enabled again iff at least one lock is requested
*/
ret = pm_runtime_put(&pdev->dev);
if (ret < 0)
goto iounmap_base;
/* one of the four lsb's must be set, and nothing else */
if (hweight_long(i & 0xf) != 1 || i > 8) {
ret = -EINVAL;
goto iounmap_base;
}
num_locks = i * 32; /* actual number of locks in this device */
bank = kzalloc(sizeof(*bank) + num_locks * sizeof(*hwlock), GFP_KERNEL);
if (!bank) {
ret = -ENOMEM;
goto iounmap_base;
}
platform_set_drvdata(pdev, bank);
for (i = 0, hwlock = &bank->lock[0]; i < num_locks; i++, hwlock++)
hwlock->priv = io_base + LOCK_BASE_OFFSET + sizeof(u32) * i;
ret = hwspin_lock_register(bank, &pdev->dev, &omap_hwspinlock_ops,
base_id, num_locks);
if (ret)
goto reg_fail;
return 0;
reg_fail:
kfree(bank);
iounmap_base:
pm_runtime_disable(&pdev->dev);
iounmap(io_base);
return ret;
}
static int omap_hwspinlock_remove(struct platform_device *pdev)
{
struct hwspinlock_device *bank = platform_get_drvdata(pdev);
void __iomem *io_base = bank->lock[0].priv - LOCK_BASE_OFFSET;
int ret;
ret = hwspin_lock_unregister(bank);
if (ret) {
dev_err(&pdev->dev, "%s failed: %d\n", __func__, ret);
return ret;
}
pm_runtime_disable(&pdev->dev);
iounmap(io_base);
kfree(bank);
return 0;
}
static const struct of_device_id omap_hwspinlock_of_match[] = {
{ .compatible = "ti,omap4-hwspinlock", },
{ /* end */ },
};
MODULE_DEVICE_TABLE(of, omap_hwspinlock_of_match);
static struct platform_driver omap_hwspinlock_driver = {
.probe = omap_hwspinlock_probe,
.remove = omap_hwspinlock_remove,
.driver = {
.name = "omap_hwspinlock",
.of_match_table = of_match_ptr(omap_hwspinlock_of_match),
},
};
static int __init omap_hwspinlock_init(void)
{
return platform_driver_register(&omap_hwspinlock_driver);
}
/* board init code might need to reserve hwspinlocks for predefined purposes */
postcore_initcall(omap_hwspinlock_init);
static void __exit omap_hwspinlock_exit(void)
{
platform_driver_unregister(&omap_hwspinlock_driver);
}
module_exit(omap_hwspinlock_exit);
MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("Hardware spinlock driver for OMAP");
MODULE_AUTHOR("Simon Que <sque@ti.com>");
MODULE_AUTHOR("Hari Kanigeri <h-kanigeri2@ti.com>");
MODULE_AUTHOR("Ohad Ben-Cohen <ohad@wizery.com>");
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