Re: [PATCH] rtw88: pci: Move a mass of jobs in hw IRQ to soft IRQ
Tony Chuang 於 2019年8月16日 週五 下午4:07寫道：
>
> Hi,
>
> A few more questions below
>
> > > From: Jian-Hong Pan [mailto:jian-h...@endlessm.com]
> > >
> > > There is a mass of jobs between spin lock and unlock in the hardware
> > > IRQ which will occupy much time originally. To make system work more
> > > efficiently, this patch moves the jobs to the soft IRQ (bottom half) to
> > > reduce the time in hardware IRQ.
> > >
> > > Signed-off-by: Jian-Hong Pan
> > > ---
> > > drivers/net/wireless/realtek/rtw88/pci.c | 36 +++-
> > > 1 file changed, 29 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/drivers/net/wireless/realtek/rtw88/pci.c
> > > b/drivers/net/wireless/realtek/rtw88/pci.c
> > > index 00ef229552d5..355606b167c6 100644
> > > --- a/drivers/net/wireless/realtek/rtw88/pci.c
> > > +++ b/drivers/net/wireless/realtek/rtw88/pci.c
> > > @@ -866,12 +866,29 @@ static irqreturn_t rtw_pci_interrupt_handler(int
> > irq,
> > > void *dev)
> > > {
> > > struct rtw_dev *rtwdev = dev;
> > > struct rtw_pci *rtwpci = (struct rtw_pci *)rtwdev->priv;
> > > - u32 irq_status[4];
> > > + unsigned long flags;
> > >
> > > - spin_lock(>irq_lock);
> > > + spin_lock_irqsave(>irq_lock, flags);
>
> I think you can use 'spin_lock()' here as it's in IRQ context?
Ah! You are right! The interrupts are already disabled in the
interrupt handler. So, there is no need to disable more once. I can
tweak it.
> > > if (!rtwpci->irq_enabled)
> > > goto out;
> > >
> > > + /* disable RTW PCI interrupt to avoid more interrupts before the end
> > > of
> > > +* thread function
> > > +*/
> > > + rtw_pci_disable_interrupt(rtwdev, rtwpci);
>
>
> Why do we need rtw_pci_disable_interrupt() here.
> Have you done any experiment and decided to add this.
> If you have can you share your results to me?
I got this idea "Avoid back to back interrupt" from Intel WiFi's driver.
https://elixir.bootlin.com/linux/v5.3-rc4/source/drivers/net/wireless/intel/iwlwifi/pcie/rx.c#L2071
So, I disable rtw_pci interrupt here in first half IRQ. (Re-enable in
bottom half)
>
> > > +out:
> > > + spin_unlock_irqrestore(>irq_lock, flags);
>
> spin_unlock()
>
> > > +
> > > + return IRQ_WAKE_THREAD;
> > > +}
> > > +
> > > +static irqreturn_t rtw_pci_interrupt_threadfn(int irq, void *dev)
> > > +{
> > > + struct rtw_dev *rtwdev = dev;
> > > + struct rtw_pci *rtwpci = (struct rtw_pci *)rtwdev->priv;
> > > + unsigned long flags;
> > > + u32 irq_status[4];
> > > +
> > > rtw_pci_irq_recognized(rtwdev, rtwpci, irq_status);
> > >
> > > if (irq_status[0] & IMR_MGNTDOK)
> > > @@ -891,8 +908,11 @@ static irqreturn_t rtw_pci_interrupt_handler(int
> > irq,
> > > void *dev)
> > > if (irq_status[0] & IMR_ROK)
> > > rtw_pci_rx_isr(rtwdev, rtwpci, RTW_RX_QUEUE_MPDU);
> > >
> > > -out:
> > > - spin_unlock(>irq_lock);
> > > + /* all of the jobs for this interrupt have been done */
> > > + spin_lock_irqsave(>irq_lock, flags);
> >
> > Shouldn't we protect the ISRs above?
> >
> > This patch could actually reduce the time of IRQ.
> > But I think I need to further test it with PCI MSI interrupt.
> > https://patchwork.kernel.org/patch/11081539/
> >
> > Maybe we could drop the "rtw_pci_[enable/disable]_interrupt" when MSI
> > Is enabled with this patch.
> >
> > > + if (rtw_flag_check(rtwdev, RTW_FLAG_RUNNING))
> > > + rtw_pci_enable_interrupt(rtwdev, rtwpci);
Then, re-enable rtw_pci interrupt here in bottom half of the IRQ.
Here is the place where Intel WiFi re-enable interrupts.
https://elixir.bootlin.com/linux/v5.3-rc4/source/drivers/net/wireless/intel/iwlwifi/pcie/rx.c#L1959
Now, we can go back to the question "Shouldn't we protect the ISRs above?"
1. What does the lock: rtwpci->irq_lock protect for?
According to the code, seems only rtw_pci interrupt's state which is
enabled or not.
2. How about the ISRs you mentioned?
This part will only be executed if there is a fresh rtw_pci interrupt.
The first half already disabled rtw_pci interrupt, so there is no more
fresh rtw_pci interrupt until rtw_pci interrupt is enabled again.
Therefor, the rtwpci->irq_lock only wraps the rtw_pci interrupt
enablement.
If there is any more entry that I missed and will interfere, please let me know.
Thank you
Jian-Hong Pan
RE: [PATCH] rtw88: pci: Move a mass of jobs in hw IRQ to soft IRQ
Hi,
A few more questions below
> > From: Jian-Hong Pan [mailto:jian-h...@endlessm.com]
> >
> > There is a mass of jobs between spin lock and unlock in the hardware
> > IRQ which will occupy much time originally. To make system work more
> > efficiently, this patch moves the jobs to the soft IRQ (bottom half) to
> > reduce the time in hardware IRQ.
> >
> > Signed-off-by: Jian-Hong Pan
> > ---
> > drivers/net/wireless/realtek/rtw88/pci.c | 36 +++-
> > 1 file changed, 29 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/net/wireless/realtek/rtw88/pci.c
> > b/drivers/net/wireless/realtek/rtw88/pci.c
> > index 00ef229552d5..355606b167c6 100644
> > --- a/drivers/net/wireless/realtek/rtw88/pci.c
> > +++ b/drivers/net/wireless/realtek/rtw88/pci.c
> > @@ -866,12 +866,29 @@ static irqreturn_t rtw_pci_interrupt_handler(int
> irq,
> > void *dev)
> > {
> > struct rtw_dev *rtwdev = dev;
> > struct rtw_pci *rtwpci = (struct rtw_pci *)rtwdev->priv;
> > - u32 irq_status[4];
> > + unsigned long flags;
> >
> > - spin_lock(>irq_lock);
> > + spin_lock_irqsave(>irq_lock, flags);
I think you can use 'spin_lock()' here as it's in IRQ context?
> > if (!rtwpci->irq_enabled)
> > goto out;
> >
> > + /* disable RTW PCI interrupt to avoid more interrupts before the end of
> > +* thread function
> > +*/
> > + rtw_pci_disable_interrupt(rtwdev, rtwpci);
Why do we need rtw_pci_disable_interrupt() here.
Have you done any experiment and decided to add this.
If you have can you share your results to me?
> > +out:
> > + spin_unlock_irqrestore(>irq_lock, flags);
spin_unlock()
> > +
> > + return IRQ_WAKE_THREAD;
> > +}
> > +
> > +static irqreturn_t rtw_pci_interrupt_threadfn(int irq, void *dev)
> > +{
> > + struct rtw_dev *rtwdev = dev;
> > + struct rtw_pci *rtwpci = (struct rtw_pci *)rtwdev->priv;
> > + unsigned long flags;
> > + u32 irq_status[4];
> > +
> > rtw_pci_irq_recognized(rtwdev, rtwpci, irq_status);
> >
> > if (irq_status[0] & IMR_MGNTDOK)
> > @@ -891,8 +908,11 @@ static irqreturn_t rtw_pci_interrupt_handler(int
> irq,
> > void *dev)
> > if (irq_status[0] & IMR_ROK)
> > rtw_pci_rx_isr(rtwdev, rtwpci, RTW_RX_QUEUE_MPDU);
> >
> > -out:
> > - spin_unlock(>irq_lock);
> > + /* all of the jobs for this interrupt have been done */
> > + spin_lock_irqsave(>irq_lock, flags);
>
> Shouldn't we protect the ISRs above?
>
> This patch could actually reduce the time of IRQ.
> But I think I need to further test it with PCI MSI interrupt.
> https://patchwork.kernel.org/patch/11081539/
>
> Maybe we could drop the "rtw_pci_[enable/disable]_interrupt" when MSI
> Is enabled with this patch.
>
> > + if (rtw_flag_check(rtwdev, RTW_FLAG_RUNNING))
> > + rtw_pci_enable_interrupt(rtwdev, rtwpci);
> > + spin_unlock_irqrestore(>irq_lock, flags);
> >
> > return IRQ_HANDLED;
> > }
> > @@ -1152,8 +1172,10 @@ static int rtw_pci_probe(struct pci_dev *pdev,
> > goto err_destroy_pci;
> > }
> >
> > - ret = request_irq(pdev->irq, _pci_interrupt_handler,
> > - IRQF_SHARED, KBUILD_MODNAME, rtwdev);
> > + ret = devm_request_threaded_irq(rtwdev->dev, pdev->irq,
> > + rtw_pci_interrupt_handler,
> > + rtw_pci_interrupt_threadfn,
> > + IRQF_SHARED, KBUILD_MODNAME, rtwdev);
> > if (ret) {
> > ieee80211_unregister_hw(hw);
> > goto err_destroy_pci;
> > @@ -1192,7 +1214,7 @@ static void rtw_pci_remove(struct pci_dev
> *pdev)
> > rtw_pci_disable_interrupt(rtwdev, rtwpci);
> > rtw_pci_destroy(rtwdev, pdev);
> > rtw_pci_declaim(rtwdev, pdev);
> > - free_irq(rtwpci->pdev->irq, rtwdev);
> > + devm_free_irq(rtwdev->dev, rtwpci->pdev->irq, rtwdev);
> > rtw_core_deinit(rtwdev);
> > ieee80211_free_hw(hw);
> > }
> > --
> > 2.20.1
>
> Yan-Hsuan
>
Thanks
Yan-Hsuan
RE: [PATCH] rtw88: pci: Move a mass of jobs in hw IRQ to soft IRQ
> From: Jian-Hong Pan [mailto:jian-h...@endlessm.com]
>
> There is a mass of jobs between spin lock and unlock in the hardware
> IRQ which will occupy much time originally. To make system work more
> efficiently, this patch moves the jobs to the soft IRQ (bottom half) to
> reduce the time in hardware IRQ.
>
> Signed-off-by: Jian-Hong Pan
> ---
> drivers/net/wireless/realtek/rtw88/pci.c | 36 +++-
> 1 file changed, 29 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/net/wireless/realtek/rtw88/pci.c
> b/drivers/net/wireless/realtek/rtw88/pci.c
> index 00ef229552d5..355606b167c6 100644
> --- a/drivers/net/wireless/realtek/rtw88/pci.c
> +++ b/drivers/net/wireless/realtek/rtw88/pci.c
> @@ -866,12 +866,29 @@ static irqreturn_t rtw_pci_interrupt_handler(int irq,
> void *dev)
> {
> struct rtw_dev *rtwdev = dev;
> struct rtw_pci *rtwpci = (struct rtw_pci *)rtwdev->priv;
> - u32 irq_status[4];
> + unsigned long flags;
>
> - spin_lock(>irq_lock);
> + spin_lock_irqsave(>irq_lock, flags);
> if (!rtwpci->irq_enabled)
> goto out;
>
> + /* disable RTW PCI interrupt to avoid more interrupts before the end of
> + * thread function
> + */
> + rtw_pci_disable_interrupt(rtwdev, rtwpci);
> +out:
> + spin_unlock_irqrestore(>irq_lock, flags);
> +
> + return IRQ_WAKE_THREAD;
> +}
> +
> +static irqreturn_t rtw_pci_interrupt_threadfn(int irq, void *dev)
> +{
> + struct rtw_dev *rtwdev = dev;
> + struct rtw_pci *rtwpci = (struct rtw_pci *)rtwdev->priv;
> + unsigned long flags;
> + u32 irq_status[4];
> +
> rtw_pci_irq_recognized(rtwdev, rtwpci, irq_status);
>
> if (irq_status[0] & IMR_MGNTDOK)
> @@ -891,8 +908,11 @@ static irqreturn_t rtw_pci_interrupt_handler(int irq,
> void *dev)
> if (irq_status[0] & IMR_ROK)
> rtw_pci_rx_isr(rtwdev, rtwpci, RTW_RX_QUEUE_MPDU);
>
> -out:
> - spin_unlock(>irq_lock);
> + /* all of the jobs for this interrupt have been done */
> + spin_lock_irqsave(>irq_lock, flags);
Shouldn't we protect the ISRs above?
This patch could actually reduce the time of IRQ.
But I think I need to further test it with PCI MSI interrupt.
https://patchwork.kernel.org/patch/11081539/
Maybe we could drop the "rtw_pci_[enable/disable]_interrupt" when MSI
Is enabled with this patch.
> + if (rtw_flag_check(rtwdev, RTW_FLAG_RUNNING))
> + rtw_pci_enable_interrupt(rtwdev, rtwpci);
> + spin_unlock_irqrestore(>irq_lock, flags);
>
> return IRQ_HANDLED;
> }
> @@ -1152,8 +1172,10 @@ static int rtw_pci_probe(struct pci_dev *pdev,
> goto err_destroy_pci;
> }
>
> - ret = request_irq(pdev->irq, _pci_interrupt_handler,
> - IRQF_SHARED, KBUILD_MODNAME, rtwdev);
> + ret = devm_request_threaded_irq(rtwdev->dev, pdev->irq,
> + rtw_pci_interrupt_handler,
> + rtw_pci_interrupt_threadfn,
> + IRQF_SHARED, KBUILD_MODNAME, rtwdev);
> if (ret) {
> ieee80211_unregister_hw(hw);
> goto err_destroy_pci;
> @@ -1192,7 +1214,7 @@ static void rtw_pci_remove(struct pci_dev *pdev)
> rtw_pci_disable_interrupt(rtwdev, rtwpci);
> rtw_pci_destroy(rtwdev, pdev);
> rtw_pci_declaim(rtwdev, pdev);
> - free_irq(rtwpci->pdev->irq, rtwdev);
> + devm_free_irq(rtwdev->dev, rtwpci->pdev->irq, rtwdev);
> rtw_core_deinit(rtwdev);
> ieee80211_free_hw(hw);
> }
> --
> 2.20.1
Yan-Hsuan
