Commit db217334 authored by Chris Leech's avatar Chris Leech Committed by David S. Miller
Browse files

[I/OAT]: Setup the networking subsystem as a DMA client



Attempts to allocate per-CPU DMA channels
Signed-off-by: default avatarChris Leech <christopher.leech@intel.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 57c651f7
......@@ -10,6 +10,18 @@ config DMA_ENGINE
DMA engines offload copy operations from the CPU to dedicated
hardware, allowing the copies to happen asynchronously.
comment "DMA Clients"
config NET_DMA
bool "Network: TCP receive copy offload"
depends on DMA_ENGINE && NET
default y
---help---
This enables the use of DMA engines in the network stack to
offload receive copy-to-user operations, freeing CPU cycles.
Since this is the main user of the DMA engine, it should be enabled;
say Y here.
comment "DMA Devices"
config INTEL_IOATDMA
......
......@@ -37,6 +37,7 @@
#include <linux/config.h>
#include <linux/device.h>
#include <linux/percpu.h>
#include <linux/dmaengine.h>
struct divert_blk;
struct vlan_group;
......@@ -593,6 +594,9 @@ struct softnet_data
struct sk_buff *completion_queue;
struct net_device backlog_dev; /* Sorry. 8) */
#ifdef CONFIG_NET_DMA
struct dma_chan *net_dma;
#endif
};
DECLARE_PER_CPU(struct softnet_data,softnet_data);
......
/*
* Copyright(c) 2004 - 2006 Intel Corporation. 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.
*
* 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.
*
* You should have received a copy of the GNU General Public License along with
* this program; if not, write to the Free Software Foundation, Inc., 59
* Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* The full GNU General Public License is included in this distribution in the
* file called COPYING.
*/
#ifndef NETDMA_H
#define NETDMA_H
#include <linux/config.h>
#ifdef CONFIG_NET_DMA
#include <linux/dmaengine.h>
static inline struct dma_chan *get_softnet_dma(void)
{
struct dma_chan *chan;
rcu_read_lock();
chan = rcu_dereference(__get_cpu_var(softnet_data.net_dma));
if (chan)
dma_chan_get(chan);
rcu_read_unlock();
return chan;
}
#endif /* CONFIG_NET_DMA */
#endif /* NETDMA_H */
......@@ -115,6 +115,7 @@
#include <net/iw_handler.h>
#include <asm/current.h>
#include <linux/audit.h>
#include <linux/dmaengine.h>
/*
* The list of packet types we will receive (as opposed to discard)
......@@ -148,6 +149,12 @@ static DEFINE_SPINLOCK(ptype_lock);
static struct list_head ptype_base[16]; /* 16 way hashed list */
static struct list_head ptype_all; /* Taps */
#ifdef CONFIG_NET_DMA
static struct dma_client *net_dma_client;
static unsigned int net_dma_count;
static spinlock_t net_dma_event_lock;
#endif
/*
* The @dev_base list is protected by @dev_base_lock and the rtnl
* semaphore.
......@@ -1846,6 +1853,19 @@ static void net_rx_action(struct softirq_action *h)
}
}
out:
#ifdef CONFIG_NET_DMA
/*
* There may not be any more sk_buffs coming right now, so push
* any pending DMA copies to hardware
*/
if (net_dma_client) {
struct dma_chan *chan;
rcu_read_lock();
list_for_each_entry_rcu(chan, &net_dma_client->channels, client_node)
dma_async_memcpy_issue_pending(chan);
rcu_read_unlock();
}
#endif
local_irq_enable();
return;
......@@ -3300,6 +3320,88 @@ static int dev_cpu_callback(struct notifier_block *nfb,
}
#endif /* CONFIG_HOTPLUG_CPU */
#ifdef CONFIG_NET_DMA
/**
* net_dma_rebalance -
* This is called when the number of channels allocated to the net_dma_client
* changes. The net_dma_client tries to have one DMA channel per CPU.
*/
static void net_dma_rebalance(void)
{
unsigned int cpu, i, n;
struct dma_chan *chan;
lock_cpu_hotplug();
if (net_dma_count == 0) {
for_each_online_cpu(cpu)
rcu_assign_pointer(per_cpu(softnet_data.net_dma, cpu), NULL);
unlock_cpu_hotplug();
return;
}
i = 0;
cpu = first_cpu(cpu_online_map);
rcu_read_lock();
list_for_each_entry(chan, &net_dma_client->channels, client_node) {
n = ((num_online_cpus() / net_dma_count)
+ (i < (num_online_cpus() % net_dma_count) ? 1 : 0));
while(n) {
per_cpu(softnet_data.net_dma, cpu) = chan;
cpu = next_cpu(cpu, cpu_online_map);
n--;
}
i++;
}
rcu_read_unlock();
unlock_cpu_hotplug();
}
/**
* netdev_dma_event - event callback for the net_dma_client
* @client: should always be net_dma_client
* @chan:
* @event:
*/
static void netdev_dma_event(struct dma_client *client, struct dma_chan *chan,
enum dma_event event)
{
spin_lock(&net_dma_event_lock);
switch (event) {
case DMA_RESOURCE_ADDED:
net_dma_count++;
net_dma_rebalance();
break;
case DMA_RESOURCE_REMOVED:
net_dma_count--;
net_dma_rebalance();
break;
default:
break;
}
spin_unlock(&net_dma_event_lock);
}
/**
* netdev_dma_regiser - register the networking subsystem as a DMA client
*/
static int __init netdev_dma_register(void)
{
spin_lock_init(&net_dma_event_lock);
net_dma_client = dma_async_client_register(netdev_dma_event);
if (net_dma_client == NULL)
return -ENOMEM;
dma_async_client_chan_request(net_dma_client, num_online_cpus());
return 0;
}
#else
static int __init netdev_dma_register(void) { return -ENODEV; }
#endif /* CONFIG_NET_DMA */
/*
* Initialize the DEV module. At boot time this walks the device list and
......@@ -3353,6 +3455,8 @@ static int __init net_dev_init(void)
atomic_set(&queue->backlog_dev.refcnt, 1);
}
netdev_dma_register();
dev_boot_phase = 0;
open_softirq(NET_TX_SOFTIRQ, net_tx_action, NULL);
......
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