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Message-ID: <6511577.3326070.1416854733107.JavaMail.zimbra@redhat.com>
Date: Mon, 24 Nov 2014 13:45:33 -0500 (EST)
From: Pankaj Gupta <pagupta@...hat.com>
To: linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Cc: davem@...emloft.net, jasowang@...hat.com, dgibson@...hat.com,
vfalico@...il.com, edumazet@...gle.com, vyasevic@...hat.com,
hkchu@...gle.com, xemul@...allels.com, therbert@...gle.com,
bhutchings@...arflare.com, xii@...gle.com,
stephen@...workplumber.org, jiri@...nulli.us,
sergei shtylyov <sergei.shtylyov@...entembedded.com>
Subject: Re: [PATCH v2 net-next 2/3] tuntap: reduce the size of tun_struct
by using flex array.
Sorry! forgot to cc Michael, doing now.
>
> This patch switches to flex array to implement the flow caches, it brings
> several advantages:
>
> - Reduce the size of the tun_struct structure, which allows us to increase
> the
> upper limit of queues in future.
> - Avoid higher order memory allocation. It will be useful when switching to
> pure hashing in flow cache which may demand a larger size array in future.
>
> After this patch, the size of tun_struct on x86_64 reduced from 8512 to
> 328
>
> Signed-off-by: Jason Wang <jasowang@...hat.com>
> Signed-off-by: Pankaj Gupta <pagupta@...hat.com>
> Reviewed-by: David Gibson <dgibson@...hat.com>
> ---
> drivers/net/tun.c | 49 +++++++++++++++++++++++++++++++++++++------------
> 1 file changed, 37 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index e3fa65a..bd07a6d 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -65,6 +65,7 @@
> #include <linux/nsproxy.h>
> #include <linux/virtio_net.h>
> #include <linux/rcupdate.h>
> +#include <linux/flex_array.h>
> #include <net/ipv6.h>
> #include <net/net_namespace.h>
> #include <net/netns/generic.h>
> @@ -188,7 +189,7 @@ struct tun_struct {
> int debug;
> #endif
> spinlock_t lock;
> - struct hlist_head flows[TUN_NUM_FLOW_ENTRIES];
> + struct flex_array *flows;
> struct timer_list flow_gc_timer;
> unsigned long ageing_time;
> unsigned int numdisabled;
> @@ -249,10 +250,11 @@ static void tun_flow_flush(struct tun_struct *tun)
>
> spin_lock_bh(&tun->lock);
> for (i = 0; i < TUN_NUM_FLOW_ENTRIES; i++) {
> + struct hlist_head *h = flex_array_get(tun->flows, i);
> struct tun_flow_entry *e;
> struct hlist_node *n;
>
> - hlist_for_each_entry_safe(e, n, &tun->flows[i], hash_link)
> + hlist_for_each_entry_safe(e, n, h, hash_link)
> tun_flow_delete(tun, e);
> }
> spin_unlock_bh(&tun->lock);
> @@ -264,10 +266,11 @@ static void tun_flow_delete_by_queue(struct tun_struct
> *tun, u16 queue_index)
>
> spin_lock_bh(&tun->lock);
> for (i = 0; i < TUN_NUM_FLOW_ENTRIES; i++) {
> + struct hlist_head *h = flex_array_get(tun->flows, i);
> struct tun_flow_entry *e;
> struct hlist_node *n;
>
> - hlist_for_each_entry_safe(e, n, &tun->flows[i], hash_link) {
> + hlist_for_each_entry_safe(e, n, h, hash_link) {
> if (e->queue_index == queue_index)
> tun_flow_delete(tun, e);
> }
> @@ -287,10 +290,11 @@ static void tun_flow_cleanup(unsigned long data)
>
> spin_lock_bh(&tun->lock);
> for (i = 0; i < TUN_NUM_FLOW_ENTRIES; i++) {
> + struct hlist_head *h = flex_array_get(tun->flows, i);
> struct tun_flow_entry *e;
> struct hlist_node *n;
>
> - hlist_for_each_entry_safe(e, n, &tun->flows[i], hash_link) {
> + hlist_for_each_entry_safe(e, n, h, hash_link) {
> unsigned long this_timer;
> count++;
> this_timer = e->updated + delay;
> @@ -317,7 +321,7 @@ static void tun_flow_update(struct tun_struct *tun, u32
> rxhash,
> if (!rxhash)
> return;
> else
> - head = &tun->flows[tun_hashfn(rxhash)];
> + head = flex_array_get(tun->flows, tun_hashfn(rxhash));
>
> rcu_read_lock();
>
> @@ -380,7 +384,8 @@ static u16 tun_select_queue(struct net_device *dev,
> struct sk_buff *skb,
>
> txq = skb_get_hash(skb);
> if (txq) {
> - e = tun_flow_find(&tun->flows[tun_hashfn(txq)], txq);
> + e = tun_flow_find(flex_array_get(tun->flows,
> + tun_hashfn(txq)), txq);
> if (e) {
> tun_flow_save_rps_rxhash(e, txq);
> txq = e->queue_index;
> @@ -760,8 +765,8 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb,
> struct net_device *dev)
> rxhash = skb_get_hash(skb);
> if (rxhash) {
> struct tun_flow_entry *e;
> - e = tun_flow_find(&tun->flows[tun_hashfn(rxhash)],
> - rxhash);
> + e = tun_flow_find(flex_array_get(tun->flows,
> + tun_hashfn(rxhash)), rxhash);
> if (e)
> tun_flow_save_rps_rxhash(e, rxhash);
> }
> @@ -896,23 +901,40 @@ static const struct net_device_ops tap_netdev_ops = {
> #endif
> };
>
> -static void tun_flow_init(struct tun_struct *tun)
> +static int tun_flow_init(struct tun_struct *tun)
> {
> - int i;
> + struct flex_array *buckets;
> + int i, err;
> +
> + buckets = flex_array_alloc(sizeof(struct hlist_head),
> + TUN_NUM_FLOW_ENTRIES, GFP_KERNEL);
> + if (!buckets)
> + return -ENOMEM;
> +
> + err = flex_array_prealloc(buckets, 0, TUN_NUM_FLOW_ENTRIES, GFP_KERNEL);
> + if (err) {
> + flex_array_free(buckets);
> + return -ENOMEM;
> + }
>
> + tun->flows = buckets;
> for (i = 0; i < TUN_NUM_FLOW_ENTRIES; i++)
> - INIT_HLIST_HEAD(&tun->flows[i]);
> + INIT_HLIST_HEAD((struct hlist_head *)
> + flex_array_get(buckets, i));
>
> tun->ageing_time = TUN_FLOW_EXPIRE;
> setup_timer(&tun->flow_gc_timer, tun_flow_cleanup, (unsigned long)tun);
> mod_timer(&tun->flow_gc_timer,
> round_jiffies_up(jiffies + tun->ageing_time));
> +
> + return 0;
> }
>
> static void tun_flow_uninit(struct tun_struct *tun)
> {
> del_timer_sync(&tun->flow_gc_timer);
> tun_flow_flush(tun);
> + flex_array_free(tun->flows);
> }
>
> /* Initialize net device. */
> @@ -1674,7 +1696,10 @@ static int tun_set_iff(struct net *net, struct file
> *file, struct ifreq *ifr)
> goto err_free_dev;
>
> tun_net_init(dev);
> - tun_flow_init(tun);
> +
> + err = tun_flow_init(tun);
> + if (err < 0)
> + goto err_free_dev;
>
> dev->hw_features = NETIF_F_SG | NETIF_F_FRAGLIST |
> TUN_USER_FEATURES | NETIF_F_HW_VLAN_CTAG_TX |
> --
> 1.8.3.1
>
>
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