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[34.145.139.141]) by smtp.gmail.com with UTF8SMTPSA id af79cd13be357-80aa60dbf87sm22282785a.3.2025.09.02.15.56.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 02 Sep 2025 15:56:13 -0700 (PDT) Date: Tue, 02 Sep 2025 18:56:13 -0400 From: Willem de Bruijn To: Breno Leitao , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, kernel-team@meta.com, efault@gmx.de, calvin@wbinvd.org, Breno Leitao Message-ID: In-Reply-To: <20250902-netpoll_untangle_v3-v1-5-51a03d6411be@debian.org> References: <20250902-netpoll_untangle_v3-v1-0-51a03d6411be@debian.org> <20250902-netpoll_untangle_v3-v1-5-51a03d6411be@debian.org> Subject: Re: [PATCH 5/7] netpoll: Move SKBs pool to netconsole side Precedence: bulk X-Mailing-List: linux-rt-devel@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Breno Leitao wrote: > Since netconsole is the sole user of the SKBs pool within netpoll, move > the pool management into the netconsole driver. > > This change prevents other netpoll users from allocating and holding > onto skb pool memory unnecessarily, thereby reducing memory usage when > the pool is not required (which is all the cases except netconsole). > > The skb poll struct is still attached to the netpoll, but, eventually > this should move to the netconsole target, since it has nothing to do > with netpoll. > > Signed-off-by: Breno Leitao > --- > drivers/net/netconsole.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++-- > net/core/netpoll.c | 44 ------------------------------------ > 2 files changed, 56 insertions(+), 46 deletions(-) > > diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c > index 90e359b87469a..3fe55db07cfe5 100644 > --- a/drivers/net/netconsole.c > +++ b/drivers/net/netconsole.c > @@ -57,6 +57,19 @@ MODULE_LICENSE("GPL"); > #define MAX_EXTRADATA_ITEMS 16 > #define MAX_PRINT_CHUNK 1000 > > +/* > + * We maintain a small pool of fully-sized skbs, to make sure the > + * message gets out even in extreme OOM situations. > + */ > + > +#define MAX_SKBS 32 > +#define MAX_UDP_CHUNK 1460 > +#define MAX_SKB_SIZE \ > + (sizeof(struct ethhdr) + \ > + sizeof(struct iphdr) + \ > + sizeof(struct udphdr) + \ > + MAX_UDP_CHUNK) > + > static char config[MAX_PARAM_LENGTH]; > module_param_string(netconsole, config, MAX_PARAM_LENGTH, 0); > MODULE_PARM_DESC(netconsole, " netconsole=[src-port]@[src-ip]/[dev],[tgt-port]@/[tgt-macaddr]"); > @@ -172,6 +185,33 @@ struct netconsole_target { > char buf[MAX_PRINT_CHUNK]; > }; > > +static void refill_skbs(struct netpoll *np) > +{ > + struct sk_buff_head *skb_pool; > + struct sk_buff *skb; > + unsigned long flags; > + > + skb_pool = &np->skb_pool; > + > + spin_lock_irqsave(&skb_pool->lock, flags); > + while (skb_pool->qlen < MAX_SKBS) { > + skb = alloc_skb(MAX_SKB_SIZE, GFP_ATOMIC); > + if (!skb) > + break; > + > + __skb_queue_tail(skb_pool, skb); > + } > + spin_unlock_irqrestore(&skb_pool->lock, flags); > +} > + > +static void refill_skbs_work_handler(struct work_struct *work) > +{ > + struct netpoll *np = > + container_of(work, struct netpoll, refill_wq); > + > + refill_skbs(np); > +} > + > #ifdef CONFIG_NETCONSOLE_DYNAMIC > > static struct configfs_subsystem netconsole_subsys; > @@ -341,6 +381,20 @@ static int netpoll_parse_ip_addr(const char *str, union inet_addr *addr) > return -1; > } > > +static int setup_netpoll(struct netpoll *np) Having both netpoll_setup and setup_netpoll is a bit confusing. Maybe netconsole_setup_netpoll? > +{ > + int err; > + > + err = netpoll_setup(np); > + if (err) > + return err; > + > + refill_skbs(np); > + INIT_WORK(&np->refill_wq, refill_skbs_work_handler); > + > + return 0; > +} > + > #ifdef CONFIG_NETCONSOLE_DYNAMIC > > /* > @@ -615,7 +669,7 @@ static ssize_t enabled_store(struct config_item *item, > */ > netconsole_print_banner(&nt->np); > > - ret = netpoll_setup(&nt->np); > + ret = setup_netpoll(&nt->np); > if (ret) > goto out_unlock; > > @@ -2036,7 +2090,7 @@ static struct netconsole_target *alloc_param_target(char *target_config, > if (err) > goto fail; > > - err = netpoll_setup(&nt->np); > + err = setup_netpoll(&nt->np); > if (err) { > pr_err("Not enabling netconsole for %s%d. Netpoll setup failed\n", > NETCONSOLE_PARAM_TARGET_PREFIX, cmdline_count);