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Message-ID: <1327934734-8908-11-git-send-email-wei.liu2@citrix.com>
Date: Mon, 30 Jan 2012 14:45:28 +0000
From: Wei Liu <wei.liu2@...rix.com>
To: netdev@...r.kernel.org, xen-devel@...ts.xensource.com
CC: ian.campbell@...rix.com, konrad.wilk@...cle.com,
Wei Liu <wei.liu2@...rix.com>
Subject: [RFC PATCH V3 10/16] netback: rework of per-cpu scratch space.
If we allocate large arrays in per-cpu section, multi-page ring
feature is likely to blow up the per-cpu section. So avoid allocating
large arrays, instead we only store pointers to scratch spaces in
per-cpu section.
CPU hotplug event is also taken care of.
Signed-off-by: Wei Liu <wei.liu2@...rix.com>
---
drivers/net/xen-netback/netback.c | 140 +++++++++++++++++++++++++++----------
1 files changed, 104 insertions(+), 36 deletions(-)
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index a8d58a9..2ac9b84 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -39,6 +39,7 @@
#include <linux/kthread.h>
#include <linux/if_vlan.h>
#include <linux/udp.h>
+#include <linux/cpu.h>
#include <net/tcp.h>
@@ -49,15 +50,15 @@
#include <asm/xen/page.h>
-struct gnttab_copy *tx_copy_ops;
+DEFINE_PER_CPU(struct gnttab_copy *, tx_copy_ops);
/*
* Given MAX_BUFFER_OFFSET of 4096 the worst case is that each
* head/fragment page uses 2 copy operations because it
* straddles two buffers in the frontend.
*/
-struct gnttab_copy *grant_copy_op;
-struct xenvif_rx_meta *meta;
+DEFINE_PER_CPU(struct gnttab_copy *, grant_copy_op);
+DEFINE_PER_CPU(struct xenvif_rx_meta *, meta);
static void xenvif_idx_release(struct xenvif *vif, u16 pending_idx);
static void make_tx_response(struct xenvif *vif,
@@ -481,8 +482,8 @@ void xenvif_rx_action(struct xenvif *vif)
struct skb_cb_overlay *sco;
int need_to_notify = 0;
- struct gnttab_copy *gco = get_cpu_ptr(grant_copy_op);
- struct xenvif_rx_meta *m = get_cpu_ptr(meta);
+ struct gnttab_copy *gco = get_cpu_var(grant_copy_op);
+ struct xenvif_rx_meta *m = get_cpu_var(meta);
struct netrx_pending_operations npo = {
.copy = gco,
@@ -512,8 +513,8 @@ void xenvif_rx_action(struct xenvif *vif)
BUG_ON(npo.meta_prod > MAX_PENDING_REQS);
if (!npo.copy_prod) {
- put_cpu_ptr(gco);
- put_cpu_ptr(m);
+ put_cpu_var(grant_copy_op);
+ put_cpu_var(meta);
return;
}
@@ -599,8 +600,8 @@ void xenvif_rx_action(struct xenvif *vif)
if (!skb_queue_empty(&vif->rx_queue))
xenvif_kick_thread(vif);
- put_cpu_ptr(gco);
- put_cpu_ptr(m);
+ put_cpu_var(grant_copy_op);
+ put_cpu_var(meta);
}
void xenvif_queue_tx_skb(struct xenvif *vif, struct sk_buff *skb)
@@ -1287,12 +1288,12 @@ int xenvif_tx_action(struct xenvif *vif, int budget)
if (unlikely(!tx_work_todo(vif)))
return 0;
- tco = get_cpu_ptr(tx_copy_ops);
+ tco = get_cpu_var(tx_copy_ops);
nr_gops = xenvif_tx_build_gops(vif, tco);
if (nr_gops == 0) {
- put_cpu_ptr(tco);
+ put_cpu_var(tx_copy_ops);
return 0;
}
@@ -1301,7 +1302,7 @@ int xenvif_tx_action(struct xenvif *vif, int budget)
work_done = xenvif_tx_submit(vif, tco, budget);
- put_cpu_ptr(tco);
+ put_cpu_var(tx_copy_ops);
return work_done;
}
@@ -1452,31 +1453,97 @@ int xenvif_kthread(void *data)
return 0;
}
+static int __create_percpu_scratch_space(unsigned int cpu)
+{
+ per_cpu(tx_copy_ops, cpu) =
+ vzalloc(sizeof(struct gnttab_copy) * MAX_PENDING_REQS);
+
+ per_cpu(grant_copy_op, cpu) =
+ vzalloc(sizeof(struct gnttab_copy)
+ * 2 * XEN_NETIF_RX_RING_SIZE);
+
+ per_cpu(meta, cpu) = vzalloc(sizeof(struct xenvif_rx_meta)
+ * 2 * XEN_NETIF_RX_RING_SIZE);
+
+ if (!per_cpu(tx_copy_ops, cpu) ||
+ !per_cpu(grant_copy_op, cpu) ||
+ !per_cpu(meta, cpu))
+ return -ENOMEM;
+
+ return 0;
+}
+
+static void __free_percpu_scratch_space(unsigned int cpu)
+{
+ /* freeing NULL pointer is legit */
+ vfree(per_cpu(tx_copy_ops, cpu));
+ vfree(per_cpu(grant_copy_op, cpu));
+ vfree(per_cpu(meta, cpu));
+}
+
+static int __netback_percpu_callback(struct notifier_block *nfb,
+ unsigned long action, void *hcpu)
+{
+ unsigned int cpu = (unsigned long)hcpu;
+ int rc = NOTIFY_DONE;
+
+ switch (action) {
+ case CPU_ONLINE:
+ case CPU_ONLINE_FROZEN:
+ printk(KERN_INFO
+ "netback: CPU %x online, creating scratch space\n", cpu);
+ rc = __create_percpu_scratch_space(cpu);
+ if (rc) {
+ printk(KERN_ALERT
+ "netback: failed to create scratch space for CPU"
+ " %x\n", cpu);
+ /* FIXME: nothing more we can do here, we will
+ * print out warning message when thread or
+ * NAPI runs on this cpu. Also stop getting
+ * called in the future.
+ */
+ __free_percpu_scratch_space(cpu);
+ rc = NOTIFY_BAD;
+ } else {
+ rc = NOTIFY_OK;
+ }
+ break;
+ case CPU_DEAD:
+ case CPU_DEAD_FROZEN:
+ printk("netback: CPU %x offline, destroying scratch space\n",
+ cpu);
+ __free_percpu_scratch_space(cpu);
+ rc = NOTIFY_OK;
+ break;
+ default:
+ break;
+ }
+
+ return rc;
+}
+
+static struct notifier_block netback_notifier_block = {
+ .notifier_call = __netback_percpu_callback,
+};
static int __init netback_init(void)
{
int rc = -ENOMEM;
+ int cpu;
if (!xen_domain())
return -ENODEV;
- tx_copy_ops = __alloc_percpu(sizeof(struct gnttab_copy)
- * MAX_PENDING_REQS,
- __alignof__(struct gnttab_copy));
- if (!tx_copy_ops)
- goto failed_init;
+ /* Don't need to disable preempt here, since nobody else will
+ * touch these percpu areas during start up. */
+ for_each_online_cpu(cpu) {
+ rc = __create_percpu_scratch_space(cpu);
- grant_copy_op = __alloc_percpu(sizeof(struct gnttab_copy)
- * 2 * XEN_NETIF_RX_RING_SIZE,
- __alignof__(struct gnttab_copy));
- if (!grant_copy_op)
- goto failed_init_gco;
+ if (rc)
+ goto failed_init;
+ }
- meta = __alloc_percpu(sizeof(struct xenvif_rx_meta)
- * 2 * XEN_NETIF_RX_RING_SIZE,
- __alignof__(struct xenvif_rx_meta));
- if (!meta)
- goto failed_init_meta;
+ register_hotcpu_notifier(&netback_notifier_block);
rc = page_pool_init();
if (rc)
@@ -1491,25 +1558,26 @@ static int __init netback_init(void)
failed_init_xenbus:
page_pool_destroy();
failed_init_pool:
- free_percpu(meta);
-failed_init_meta:
- free_percpu(grant_copy_op);
-failed_init_gco:
- free_percpu(tx_copy_ops);
+ for_each_online_cpu(cpu)
+ __free_percpu_scratch_space(cpu);
failed_init:
return rc;
-
}
module_init(netback_init);
static void __exit netback_exit(void)
{
+ int cpu;
+
xenvif_xenbus_exit();
page_pool_destroy();
- free_percpu(meta);
- free_percpu(grant_copy_op);
- free_percpu(tx_copy_ops);
+
+ unregister_hotcpu_notifier(&netback_notifier_block);
+
+ /* Since we're here, nobody else will touch per-cpu area. */
+ for_each_online_cpu(cpu)
+ __free_percpu_scratch_space(cpu);
}
module_exit(netback_exit);
--
1.7.2.5
--
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