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
cardbus.c
/*
* cardbus.c -- 16-bit PCMCIA core support
*
* 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.
*
* The initial developer of the original code is David A. Hinds
* <dahinds@users.sourceforge.net>. Portions created by David A. Hinds
* are Copyright (C) 1999 David A. Hinds. All Rights Reserved.
*
* (C) 1999 David A. Hinds
*/
/*
* Cardbus handling has been re-written to be more of a PCI bridge thing,
* and the PCI code basically does all the resource handling.
*
* Linus, Jan 2000
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/pci.h>
#include <pcmcia/ss.h>
static void cardbus_config_irq_and_cls(struct pci_bus *bus, int irq)
{
struct pci_dev *dev;
list_for_each_entry(dev, &bus->devices, bus_list) {
u8 irq_pin;
/*
* Since there is only one interrupt available to
* CardBus devices, all devices downstream of this
* device must be using this IRQ.
*/
pci_read_config_byte(dev, PCI_INTERRUPT_PIN, &irq_pin);
if (irq_pin) {
dev->irq = irq;
pci_write_config_byte(dev, PCI_INTERRUPT_LINE, dev->irq);
}
/*
* Some controllers transfer very slowly with 0 CLS.
* Configure it. This may fail as CLS configuration
* is mandatory only for MWI.
*/
pci_set_cacheline_size(dev);
if (dev->subordinate)
cardbus_config_irq_and_cls(dev->subordinate, irq);
}
}
/**
* cb_alloc() - add CardBus device
* @s: the pcmcia_socket where the CardBus device is located
*
* cb_alloc() allocates the kernel data structures for a Cardbus device
* and handles the lowest level PCI device setup issues.
*/
int __ref cb_alloc(struct pcmcia_socket *s)
{
struct pci_bus *bus = s->cb_dev->subordinate;
struct pci_dev *dev;
unsigned int max, pass;
pci_lock_rescan_remove();
s->functions = pci_scan_slot(bus, PCI_DEVFN(0, 0));
pci_fixup_cardbus(bus);
max = bus->busn_res.start;
for (pass = 0; pass < 2; pass++)
for_each_pci_bridge(dev, bus)
max = pci_scan_bridge(bus, dev, max, pass);
/*
* Size all resources below the CardBus controller.
*/
pci_bus_size_bridges(bus);
pci_bus_assign_resources(bus);
cardbus_config_irq_and_cls(bus, s->pci_irq);
/* socket specific tune function */
if (s->tune_bridge)
s->tune_bridge(s, bus);
pci_bus_add_devices(bus);
pci_unlock_rescan_remove();
return 0;
}
/**
* cb_free() - remove CardBus device
* @s: the pcmcia_socket where the CardBus device was located
*
* cb_free() handles the lowest level PCI device cleanup.
*/
void cb_free(struct pcmcia_socket *s)
{
struct pci_dev *bridge, *dev, *tmp;
struct pci_bus *bus;
bridge = s->cb_dev;
if (!bridge)
return;
bus = bridge->subordinate;
if (!bus)
return;
pci_lock_rescan_remove();
list_for_each_entry_safe(dev, tmp, &bus->devices, bus_list)
pci_stop_and_remove_bus_device(dev);
pci_unlock_rescan_remove();
}
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