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
i2c-pca-isa.c
/*
* i2c-pca-isa.c driver for PCA9564 on ISA boards
* Copyright (C) 2004 Arcom Control Systems
* Copyright (C) 2008 Pengutronix
*
* 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.
*
* 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/ioport.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/delay.h>
#include <linux/jiffies.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/wait.h>
#include <linux/isa.h>
#include <linux/i2c.h>
#include <linux/i2c-algo-pca.h>
#include <linux/io.h>
#include <asm/irq.h>
#define DRIVER "i2c-pca-isa"
#define IO_SIZE 4
static unsigned long base;
static int irq = -1;
/* Data sheet recommends 59kHz for 100kHz operation due to variation
* in the actual clock rate */
static int clock = 59000;
static struct i2c_adapter pca_isa_ops;
static wait_queue_head_t pca_wait;
static void pca_isa_writebyte(void *pd, int reg, int val)
{
#ifdef DEBUG_IO
static char *names[] = { "T/O", "DAT", "ADR", "CON" };
printk(KERN_DEBUG "*** write %s at %#lx <= %#04x\n", names[reg],
base+reg, val);
#endif
outb(val, base+reg);
}
static int pca_isa_readbyte(void *pd, int reg)
{
int res = inb(base+reg);
#ifdef DEBUG_IO
{
static char *names[] = { "STA", "DAT", "ADR", "CON" };
printk(KERN_DEBUG "*** read %s => %#04x\n", names[reg], res);
}
#endif
return res;
}
static int pca_isa_waitforcompletion(void *pd)
{
unsigned long timeout;
long ret;
if (irq > -1) {
ret = wait_event_timeout(pca_wait,
pca_isa_readbyte(pd, I2C_PCA_CON)
& I2C_PCA_CON_SI, pca_isa_ops.timeout);
} else {
/* Do polling */
timeout = jiffies + pca_isa_ops.timeout;
do {
ret = time_before(jiffies, timeout);
if (pca_isa_readbyte(pd, I2C_PCA_CON)
& I2C_PCA_CON_SI)
break;
udelay(100);
} while (ret);
}
return ret > 0;
}
static void pca_isa_resetchip(void *pd)
{
/* apparently only an external reset will do it. not a lot can be done */
printk(KERN_WARNING DRIVER ": Haven't figured out how to do a reset yet\n");
}
static irqreturn_t pca_handler(int this_irq, void *dev_id) {
wake_up(&pca_wait);
return IRQ_HANDLED;
}
static struct i2c_algo_pca_data pca_isa_data = {
/* .data intentionally left NULL, not needed with ISA */
.write_byte = pca_isa_writebyte,
.read_byte = pca_isa_readbyte,
.wait_for_completion = pca_isa_waitforcompletion,
.reset_chip = pca_isa_resetchip,
};
static struct i2c_adapter pca_isa_ops = {
.owner = THIS_MODULE,
.algo_data = &pca_isa_data,
.name = "PCA9564/PCA9665 ISA Adapter",
.timeout = HZ,
};
static int pca_isa_match(struct device *dev, unsigned int id)
{
int match = base != 0;
if (match) {
if (irq <= -1)
dev_warn(dev, "Using polling mode (specify irq)\n");
} else
dev_err(dev, "Please specify I/O base\n");
return match;
}
static int pca_isa_probe(struct device *dev, unsigned int id)
{
init_waitqueue_head(&pca_wait);
dev_info(dev, "i/o base %#08lx. irq %d\n", base, irq);
#ifdef CONFIG_PPC
if (check_legacy_ioport(base)) {
dev_err(dev, "I/O address %#08lx is not available\n", base);
goto out;
}
#endif
if (!request_region(base, IO_SIZE, "i2c-pca-isa")) {
dev_err(dev, "I/O address %#08lx is in use\n", base);
goto out;
}
if (irq > -1) {
if (request_irq(irq, pca_handler, 0, "i2c-pca-isa", &pca_isa_ops) < 0) {
dev_err(dev, "Request irq%d failed\n", irq);
goto out_region;
}
}
pca_isa_data.i2c_clock = clock;
if (i2c_pca_add_bus(&pca_isa_ops) < 0) {
dev_err(dev, "Failed to add i2c bus\n");
goto out_irq;
}
return 0;
out_irq:
if (irq > -1)
free_irq(irq, &pca_isa_ops);
out_region:
release_region(base, IO_SIZE);
out:
return -ENODEV;
}
static int pca_isa_remove(struct device *dev, unsigned int id)
{
i2c_del_adapter(&pca_isa_ops);
if (irq > -1) {
disable_irq(irq);
free_irq(irq, &pca_isa_ops);
}
release_region(base, IO_SIZE);
return 0;
}
static struct isa_driver pca_isa_driver = {
.match = pca_isa_match,
.probe = pca_isa_probe,
.remove = pca_isa_remove,
.driver = {
.owner = THIS_MODULE,
.name = DRIVER,
}
};
MODULE_AUTHOR("Ian Campbell <icampbell@arcom.com>");
MODULE_DESCRIPTION("ISA base PCA9564/PCA9665 driver");
MODULE_LICENSE("GPL");
module_param_hw(base, ulong, ioport, 0);
MODULE_PARM_DESC(base, "I/O base address");
module_param_hw(irq, int, irq, 0);
MODULE_PARM_DESC(irq, "IRQ");
module_param(clock, int, 0);
MODULE_PARM_DESC(clock, "Clock rate in hertz.\n\t\t"
"For PCA9564: 330000,288000,217000,146000,"
"88000,59000,44000,36000\n"
"\t\tFor PCA9665:\tStandard: 60300 - 100099\n"
"\t\t\t\tFast: 100100 - 400099\n"
"\t\t\t\tFast+: 400100 - 10000099\n"
"\t\t\t\tTurbo: Up to 1265800");
module_isa_driver(pca_isa_driver, 1);
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