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Message-ID: <ZuR5jU3BGbsut-q6@mini-arch>
Date: Fri, 13 Sep 2024 10:42:37 -0700
From: Stanislav Fomichev <stfomichev@...il.com>
To: Joe Damato <jdamato@...tly.com>
Cc: netdev@...r.kernel.org, mkarsten@...terloo.ca, kuba@...nel.org,
skhawaja@...gle.com, sdf@...ichev.me, bjorn@...osinc.com,
amritha.nambiar@...el.com, sridhar.samudrala@...el.com,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
Jonathan Corbet <corbet@....net>, Jiri Pirko <jiri@...nulli.us>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
Lorenzo Bianconi <lorenzo@...nel.org>,
David Ahern <dsahern@...nel.org>,
Johannes Berg <johannes.berg@...el.com>,
"open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
open list <linux-kernel@...r.kernel.org>
Subject: Re: [RFC net-next v3 5/9] net: napi: Add napi_config
On 09/12, Joe Damato wrote:
> Add a persistent NAPI config area for NAPI configuration to the core.
> Drivers opt-in to setting the storage for a NAPI by passing an index
> when calling netif_napi_add_storage.
>
> napi_config is allocated in alloc_netdev_mqs, freed in free_netdev
> (after the NAPIs are deleted), and set to 0 when napi_enable is called.
>
> Drivers which implement call netif_napi_add_storage will have persistent
> NAPI IDs.
>
> Signed-off-by: Joe Damato <jdamato@...tly.com>
> ---
> .../networking/net_cachelines/net_device.rst | 1 +
> include/linux/netdevice.h | 34 +++++++++
> net/core/dev.c | 74 +++++++++++++++++--
> net/core/dev.h | 12 +++
> 4 files changed, 113 insertions(+), 8 deletions(-)
>
> diff --git a/Documentation/networking/net_cachelines/net_device.rst b/Documentation/networking/net_cachelines/net_device.rst
> index 3d02ae79c850..11d659051f5e 100644
> --- a/Documentation/networking/net_cachelines/net_device.rst
> +++ b/Documentation/networking/net_cachelines/net_device.rst
> @@ -183,3 +183,4 @@ struct hlist_head page_pools
> struct dim_irq_moder* irq_moder
> unsigned_long gro_flush_timeout
> u32 napi_defer_hard_irqs
> +struct napi_config* napi_config
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index 3e07ab8e0295..08afc96179f9 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -342,6 +342,15 @@ struct gro_list {
> */
> #define GRO_HASH_BUCKETS 8
>
> +/*
> + * Structure for per-NAPI storage
> + */
> +struct napi_config {
> + u64 gro_flush_timeout;
> + u32 defer_hard_irqs;
> + unsigned int napi_id;
> +};
> +
> /*
> * Structure for NAPI scheduling similar to tasklet but with weighting
> */
> @@ -379,6 +388,8 @@ struct napi_struct {
> int irq;
> unsigned long gro_flush_timeout;
> u32 defer_hard_irqs;
> + int index;
> + struct napi_config *config;
> };
>
> enum {
> @@ -2011,6 +2022,9 @@ enum netdev_reg_state {
> * @dpll_pin: Pointer to the SyncE source pin of a DPLL subsystem,
> * where the clock is recovered.
> *
> + * @napi_config: An array of napi_config structures containing per-NAPI
> + * settings.
> + *
> * FIXME: cleanup struct net_device such that network protocol info
> * moves out.
> */
> @@ -2400,6 +2414,7 @@ struct net_device {
> struct dim_irq_moder *irq_moder;
> unsigned long gro_flush_timeout;
> u32 napi_defer_hard_irqs;
> + struct napi_config *napi_config;
>
> u8 priv[] ____cacheline_aligned
> __counted_by(priv_len);
> @@ -2650,6 +2665,23 @@ netif_napi_add_tx_weight(struct net_device *dev,
> netif_napi_add_weight(dev, napi, poll, weight);
> }
>
> +/**
> + * netif_napi_add_storage - initialize a NAPI context and set storage area
> + * @dev: network device
> + * @napi: NAPI context
> + * @poll: polling function
> + * @weight: the poll weight of this NAPI
> + * @index: the NAPI index
> + */
> +static inline void
> +netif_napi_add_storage(struct net_device *dev, struct napi_struct *napi,
> + int (*poll)(struct napi_struct *, int), int index)
> +{
> + napi->index = index;
> + napi->config = &dev->napi_config[index];
> + netif_napi_add_weight(dev, napi, poll, NAPI_POLL_WEIGHT);
> +}
> +
> /**
> * netif_napi_add_tx() - initialize a NAPI context to be used for Tx only
> * @dev: network device
> @@ -2685,6 +2717,8 @@ void __netif_napi_del(struct napi_struct *napi);
> */
> static inline void netif_napi_del(struct napi_struct *napi)
> {
> + napi->config = NULL;
> + napi->index = -1;
> __netif_napi_del(napi);
> synchronize_net();
> }
> diff --git a/net/core/dev.c b/net/core/dev.c
> index f2fd503516de..ca2227d0b8ed 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -6493,6 +6493,18 @@ EXPORT_SYMBOL(napi_busy_loop);
>
> #endif /* CONFIG_NET_RX_BUSY_POLL */
>
> +static void napi_hash_add_with_id(struct napi_struct *napi, unsigned int napi_id)
> +{
> + spin_lock(&napi_hash_lock);
> +
> + napi->napi_id = napi_id;
> +
> + hlist_add_head_rcu(&napi->napi_hash_node,
> + &napi_hash[napi->napi_id % HASH_SIZE(napi_hash)]);
> +
> + spin_unlock(&napi_hash_lock);
> +}
> +
> static void napi_hash_add(struct napi_struct *napi)
> {
> if (test_bit(NAPI_STATE_NO_BUSY_POLL, &napi->state))
> @@ -6505,12 +6517,13 @@ static void napi_hash_add(struct napi_struct *napi)
> if (unlikely(++napi_gen_id < MIN_NAPI_ID))
> napi_gen_id = MIN_NAPI_ID;
> } while (napi_by_id(napi_gen_id));
[..]
> - napi->napi_id = napi_gen_id;
> -
> - hlist_add_head_rcu(&napi->napi_hash_node,
> - &napi_hash[napi->napi_id % HASH_SIZE(napi_hash)]);
>
> spin_unlock(&napi_hash_lock);
> +
> + napi_hash_add_with_id(napi, napi_gen_id);
nit: it is very unlikely that napi_gen_id is gonna wrap around after the
spin_unlock above, but maybe it's safer to have the following?
static void __napi_hash_add_with_id(struct napi_struct *napi, unsigned int napi_id)
{
napi->napi_id = napi_id;
hlist_add_head_rcu(&napi->napi_hash_node,
&napi_hash[napi->napi_id % HASH_SIZE(napi_hash)]);
}
static void napi_hash_add_with_id(struct napi_struct *napi, unsigned int napi_id)
{
spin_lock(&napi_hash_lock);
__napi_hash_add_with_id(...);
spin_unlock(&napi_hash_lock);
}
And use __napi_hash_add_with_id here before spin_unlock?
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