Re: [PATCH 1/2] r8169: Implement dynamic ASPM mechanism

[Kai-Heng Feng]

On Sat, Aug 7, 2021 at 2:47 AM Heiner Kallweit <hkallweit1@xxxxxxxxx> wrote:
>
> On 03.08.2021 17:28, Kai-Heng Feng wrote:
> > r8169 NICs on some platforms have abysmal speed when ASPM is enabled.
> > Same issue can be observed with older vendor drivers.
> >
> > The issue is however solved by the latest vendor driver. There's a new
> > mechanism, which disables r8169's internal ASPM when the NIC has
> > substantial network traffic, and vice versa.
> >
> > So implement the same mechanism here to resolve the issue.
> >
> > Signed-off-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>
> > ---
> >  drivers/net/ethernet/realtek/r8169_main.c | 36 +++++++++++++++++++++++
> >  1 file changed, 36 insertions(+)
> >
> > diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c
> > index c7af5bc3b8af..e257d3cd885e 100644
> > --- a/drivers/net/ethernet/realtek/r8169_main.c
> > +++ b/drivers/net/ethernet/realtek/r8169_main.c
> > @@ -624,6 +624,10 @@ struct rtl8169_private {
> >
> >       unsigned supports_gmii:1;
> >       unsigned aspm_manageable:1;
> > +     unsigned aspm_enabled:1;
> > +     struct timer_list aspm_timer;
> > +     u32 aspm_packet_count;
> > +
> >       dma_addr_t counters_phys_addr;
> >       struct rtl8169_counters *counters;
> >       struct rtl8169_tc_offsets tc_offset;
> > @@ -2671,6 +2675,8 @@ static void rtl_hw_aspm_clkreq_enable(struct rtl8169_private *tp, bool enable)
> >               RTL_W8(tp, Config5, RTL_R8(tp, Config5) & ~ASPM_en);
> >       }
> >
> > +     tp->aspm_enabled = enable;
> > +
> >       udelay(10);
> >  }
> >
> > @@ -4408,6 +4414,7 @@ static void rtl_tx(struct net_device *dev, struct rtl8169_private *tp,
> >
> >       dirty_tx = tp->dirty_tx;
> >
> > +     tp->aspm_packet_count += tp->cur_tx - dirty_tx;
> >       while (READ_ONCE(tp->cur_tx) != dirty_tx) {
> >               unsigned int entry = dirty_tx % NUM_TX_DESC;
> >               u32 status;
> > @@ -4552,6 +4559,8 @@ static int rtl_rx(struct net_device *dev, struct rtl8169_private *tp, int budget
> >               rtl8169_mark_to_asic(desc);
> >       }
> >
> > +     tp->aspm_packet_count += count;
> > +
> >       return count;
> >  }
> >
> > @@ -4659,8 +4668,31 @@ static int r8169_phy_connect(struct rtl8169_private *tp)
> >       return 0;
> >  }
> >
> > +#define ASPM_PACKET_THRESHOLD 10
> > +#define ASPM_TIMER_INTERVAL 1000
> > +
> > +static void rtl8169_aspm_timer(struct timer_list *timer)
> > +{
> > +     struct rtl8169_private *tp = from_timer(tp, timer, aspm_timer);
> > +     bool enable;
> > +
> > +     enable = tp->aspm_packet_count <= ASPM_PACKET_THRESHOLD;
> > +
> > +     if (tp->aspm_enabled != enable) {
> > +             rtl_unlock_config_regs(tp);
> > +             rtl_hw_aspm_clkreq_enable(tp, enable);
> > +             rtl_lock_config_regs(tp);
> > +     }
> > +
> > +     tp->aspm_packet_count = 0;
> > +
> > +     mod_timer(timer, jiffies + msecs_to_jiffies(ASPM_TIMER_INTERVAL));
> > +}
> > +
> >  static void rtl8169_down(struct rtl8169_private *tp)
> >  {
> > +     del_timer_sync(&tp->aspm_timer);
> > +
> >       /* Clear all task flags */
> >       bitmap_zero(tp->wk.flags, RTL_FLAG_MAX);
> >
> > @@ -4687,6 +4719,10 @@ static void rtl8169_up(struct rtl8169_private *tp)
> >       rtl_reset_work(tp);
> >
> >       phy_start(tp->phydev);
> > +
> > +     timer_setup(&tp->aspm_timer, rtl8169_aspm_timer, 0);
> > +     mod_timer(&tp->aspm_timer,
> > +               jiffies + msecs_to_jiffies(ASPM_TIMER_INTERVAL));
> >  }
> >
> >  static int rtl8169_close(struct net_device *dev)
> >
>
> I have one more question / concern regarding this workaround:
> If bigger traffic starts and results in a congestion (let's call it like that
> because we don't know in detail what happens in the chip), then it may take
> up to a second until ASPM gets disabled and traffic gets back to normal.
> This second is good enough to prevent that the timeout watchdog fires.
> However in this second supposedly traffic is very limited, if possible at all.
> Means if we have a network traffic pattern with alternating quiet and busy
> periods then we may see a significant impact on performance.
> Is this something that you tested?

No, we didn't test this scenario.
Realtek told us that dynamic ASPM is also used by Windows driver, but
I don't know the interval used by Windows driver.
For now I think it's better to stick with vendor defined value.

Kai-Heng