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Message-ID: <CAL+tcoDpNx4p8zgo_ZeqGAmVLJkMnTt9O7uidcCc9aC70ngrFg@mail.gmail.com>
Date: Tue, 14 Mar 2023 09:56:33 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Simon Horman <simon.horman@...igine.com>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
pabeni@...hat.com, ast@...nel.org, daniel@...earbox.net,
hawk@...nel.org, john.fastabend@...il.com, kuniyu@...zon.com,
liuhangbin@...il.com, xiangxia.m.yue@...il.com, jiri@...dia.com,
andy.ren@...cruise.com, bpf@...r.kernel.org,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next] net: introduce budget_squeeze to help us tune rx behavior
On Tue, Mar 14, 2023 at 4:07 AM Simon Horman <simon.horman@...igine.com> wrote:
>
> On Mon, Mar 13, 2023 at 10:05:18AM +0800, Jason Xing wrote:
> > On Sun, Mar 12, 2023 at 12:36 AM Jason Xing <kerneljasonxing@...il.com> wrote:
> > >
> > > From: Jason Xing <kernelxing@...cent.com>
> > >
> > > When we encounter some performance issue and then get lost on how
> > > to tune the budget limit and time limit in net_rx_action() function,
> > > we can separately counting both of them to avoid the confusion.
> > >
> > > Signed-off-by: Jason Xing <kernelxing@...cent.com>
> > > ---
> > > note: this commit is based on the link as below:
> > > https://lore.kernel.org/lkml/20230311151756.83302-1-kerneljasonxing@gmail.com/
> > > ---
> > > include/linux/netdevice.h | 1 +
> > > net/core/dev.c | 12 ++++++++----
> > > net/core/net-procfs.c | 9 ++++++---
> > > 3 files changed, 15 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> > > index 6a14b7b11766..5736311a2133 100644
> > > --- a/include/linux/netdevice.h
> > > +++ b/include/linux/netdevice.h
> > > @@ -3157,6 +3157,7 @@ struct softnet_data {
> > > /* stats */
> > > unsigned int processed;
> > > unsigned int time_squeeze;
> > > + unsigned int budget_squeeze;
> > > #ifdef CONFIG_RPS
> > > struct softnet_data *rps_ipi_list;
> > > #endif
> > > diff --git a/net/core/dev.c b/net/core/dev.c
> > > index 253584777101..bed7a68fdb5d 100644
> > > --- a/net/core/dev.c
> > > +++ b/net/core/dev.c
> > > @@ -6637,6 +6637,7 @@ static __latent_entropy void net_rx_action(struct softirq_action *h)
> > > unsigned long time_limit = jiffies +
> > > usecs_to_jiffies(READ_ONCE(netdev_budget_usecs));
> > > int budget = READ_ONCE(netdev_budget);
> > > + bool is_continue = true;
> >
> > I kept thinking during these days, I think it looks not that concise
> > and elegant and also the name is not that good though the function can
> > work.
> >
> > In the next submission, I'm going to choose to use 'while()' instead
> > of 'for()' suggested by Stephen.
> >
> > Does anyone else have some advice about this?
>
> What about:
>
> int done = false
>
> while (!done) {
> ...
> }
>
> Or:
>
> for (;;) {
> int done = false;
>
> ...
> if (done)
> break;
> }
>
Great, that looks much better:)
Thanks,
Jason
> >
> > Thanks,
> > Jason
> >
> > > LIST_HEAD(list);
> > > LIST_HEAD(repoll);
> > >
> > > @@ -6644,7 +6645,7 @@ static __latent_entropy void net_rx_action(struct softirq_action *h)
> > > list_splice_init(&sd->poll_list, &list);
> > > local_irq_enable();
> > >
> > > - for (;;) {
> > > + for (; is_continue;) {
> > > struct napi_struct *n;
> > >
> > > skb_defer_free_flush(sd);
> > > @@ -6662,10 +6663,13 @@ static __latent_entropy void net_rx_action(struct softirq_action *h)
> > > * Allow this to run for 2 jiffies since which will allow
> > > * an average latency of 1.5/HZ.
> > > */
> > > - if (unlikely(budget <= 0 ||
> > > - time_after_eq(jiffies, time_limit))) {
> > > + if (unlikely(budget <= 0)) {
> > > + sd->budget_squeeze++;
> > > + is_continue = false;
> > > + }
> > > + if (unlikely(time_after_eq(jiffies, time_limit))) {
> > > sd->time_squeeze++;
> > > - break;
> > > + is_continue = false;
> > > }
> > > }
> > >
> > > diff --git a/net/core/net-procfs.c b/net/core/net-procfs.c
> > > index 97a304e1957a..4d1a499d7c43 100644
> > > --- a/net/core/net-procfs.c
> > > +++ b/net/core/net-procfs.c
> > > @@ -174,14 +174,17 @@ static int softnet_seq_show(struct seq_file *seq, void *v)
> > > */
> > > seq_printf(seq,
> > > "%08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x "
> > > - "%08x %08x\n",
> > > - sd->processed, sd->dropped, sd->time_squeeze, 0,
> > > + "%08x %08x %08x %08x\n",
> > > + sd->processed, sd->dropped,
> > > + 0, /* was old way to count time squeeze */
> > > + 0,
> > > 0, 0, 0, 0, /* was fastroute */
> > > 0, /* was cpu_collision */
> > > sd->received_rps, flow_limit_count,
> > > 0, /* was len of two backlog queues */
> > > (int)seq->index,
> > > - softnet_input_pkt_queue_len(sd), softnet_process_queue_len(sd));
> > > + softnet_input_pkt_queue_len(sd), softnet_process_queue_len(sd),
> > > + sd->time_squeeze, sd->budget_squeeze);
> > > return 0;
> > > }
> > >
> > > --
> > > 2.37.3
> > >
> >
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