Re: [Intel-wired-lan] [PATCH iwl-next] igc: Get rid of spurious interrupts
On 6/20/2024 7:34 AM, Kurt Kanzenbach wrote: Can you drop this patch from your queue, please? I've found one issue with this if the number of queues is reconfigured e.g., with 'ethtool -L combined 1'. The number of vectors is not necessarily the number of rx rings. I'll update this patch and sent v2. Sure thing. Patch dropped. Thanks, Tony
Re: [Intel-wired-lan] [PATCH iwl-next] igc: Get rid of spurious interrupts
Hi Tony, On Wed Jun 12 2024, Kurt Kanzenbach wrote: > When running the igc with XDP/ZC in busy polling mode with deferral of hard > interrupts, interrupts still happen from time to time. That is caused by > the igc task watchdog which triggers Rx interrupts periodically. > > That mechanism has been introduced to overcome skb/memory allocation > failures [1]. So the Rx clean functions stop processing the Rx ring in case > of such failure. The task watchdog triggers Rx interrupts periodically in > the hope that memory became available in the mean time. > > The current behavior is undesirable for real time applications, because the > driver induced Rx interrupts trigger also the softirq processing. However, > all real time packets should be processed by the application which uses the > busy polling method. > > Therefore, only trigger the Rx interrupts in case of real allocation > failures. Introduce a new flag for signaling that condition. > > [1] - > https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/?id=3be507547e6177e5c808544bd6a2efa2c7f1d436 > > Signed-off-by: Kurt Kanzenbach Can you drop this patch from your queue, please? I've found one issue with this if the number of queues is reconfigured e.g., with 'ethtool -L combined 1'. The number of vectors is not necessarily the number of rx rings. I'll update this patch and sent v2. Thanks, Kurt signature.asc Description: PGP signature
Re: [Intel-wired-lan] [PATCH iwl-next] igc: Get rid of spurious interrupts
Sebastian Andrzej Siewior writes:
> On 2024-06-12 12:49:21 [-0700], Vinicius Costa Gomes wrote:
>> > diff --git a/drivers/net/ethernet/intel/igc/igc_main.c
>> > b/drivers/net/ethernet/intel/igc/igc_main.c
>> > index 305e05294a26..e666739dfac7 100644
>> > --- a/drivers/net/ethernet/intel/igc/igc_main.c
>> > +++ b/drivers/net/ethernet/intel/igc/igc_main.c
>> > @@ -5811,11 +5815,23 @@ static void igc_watchdog_task(struct work_struct
>> > *work)
>> >if (adapter->flags & IGC_FLAG_HAS_MSIX) {
>> >u32 eics = 0;
>> >
>> > - for (i = 0; i < adapter->num_q_vectors; i++)
>> > - eics |= adapter->q_vector[i]->eims_value;
>> > - wr32(IGC_EICS, eics);
>> > + for (i = 0; i < adapter->num_q_vectors; i++) {
>> > + struct igc_ring *rx_ring = adapter->rx_ring[i];
>> > +
>> > + if (test_bit(IGC_RING_FLAG_RX_ALLOC_FAILED,
>> > _ring->flags)) {
>>
>> Minor and optional: I guess you can replace test_bit() -> clear_bit()
>> with __test_and_clear_bit() here and below.
>
> That are two steps, first test+clear is merged into one and then __ is
> added. The former is doable but it will always lead to a write operation
> while in the common case the flag isn't set so it will be skipped.
> Adding the __ leads to an unlocked operation and I don't see how this is
> synchronized against the other writes. In fact, nobody else is doing it.
>
I just took a look at the available operations, and thought that this
one could save a few lines of code. But didn't think too deeply about
that. Thanks.
Cheers,
--
Vinicius
Re: [Intel-wired-lan] [PATCH iwl-next] igc: Get rid of spurious interrupts
On 2024-06-12 12:49:21 [-0700], Vinicius Costa Gomes wrote:
> > diff --git a/drivers/net/ethernet/intel/igc/igc_main.c
> > b/drivers/net/ethernet/intel/igc/igc_main.c
> > index 305e05294a26..e666739dfac7 100644
> > --- a/drivers/net/ethernet/intel/igc/igc_main.c
> > +++ b/drivers/net/ethernet/intel/igc/igc_main.c
> > @@ -5811,11 +5815,23 @@ static void igc_watchdog_task(struct work_struct
> > *work)
> > if (adapter->flags & IGC_FLAG_HAS_MSIX) {
> > u32 eics = 0;
> >
> > - for (i = 0; i < adapter->num_q_vectors; i++)
> > - eics |= adapter->q_vector[i]->eims_value;
> > - wr32(IGC_EICS, eics);
> > + for (i = 0; i < adapter->num_q_vectors; i++) {
> > + struct igc_ring *rx_ring = adapter->rx_ring[i];
> > +
> > + if (test_bit(IGC_RING_FLAG_RX_ALLOC_FAILED,
> > _ring->flags)) {
>
> Minor and optional: I guess you can replace test_bit() -> clear_bit()
> with __test_and_clear_bit() here and below.
That are two steps, first test+clear is merged into one and then __ is
added. The former is doable but it will always lead to a write operation
while in the common case the flag isn't set so it will be skipped.
Adding the __ leads to an unlocked operation and I don't see how this is
synchronized against the other writes. In fact, nobody else is doing it.
Sebastian
Re: [Intel-wired-lan] [PATCH iwl-next] igc: Get rid of spurious interrupts
Kurt Kanzenbach writes:
> When running the igc with XDP/ZC in busy polling mode with deferral of hard
> interrupts, interrupts still happen from time to time. That is caused by
> the igc task watchdog which triggers Rx interrupts periodically.
>
> That mechanism has been introduced to overcome skb/memory allocation
> failures [1]. So the Rx clean functions stop processing the Rx ring in case
> of such failure. The task watchdog triggers Rx interrupts periodically in
> the hope that memory became available in the mean time.
>
> The current behavior is undesirable for real time applications, because the
> driver induced Rx interrupts trigger also the softirq processing. However,
> all real time packets should be processed by the application which uses the
> busy polling method.
>
> Therefore, only trigger the Rx interrupts in case of real allocation
> failures. Introduce a new flag for signaling that condition.
>
> [1] -
> https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/?id=3be507547e6177e5c808544bd6a2efa2c7f1d436
>
> Signed-off-by: Kurt Kanzenbach
> ---
Acked-by: Vinicius Costa Gomes
> drivers/net/ethernet/intel/igc/igc.h | 1 +
> drivers/net/ethernet/intel/igc/igc_main.c | 24
> 2 files changed, 21 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/igc/igc.h
> b/drivers/net/ethernet/intel/igc/igc.h
> index 8b14c029eda1..7bfe5030e2c0 100644
> --- a/drivers/net/ethernet/intel/igc/igc.h
> +++ b/drivers/net/ethernet/intel/igc/igc.h
> @@ -682,6 +682,7 @@ enum igc_ring_flags_t {
> IGC_RING_FLAG_TX_DETECT_HANG,
> IGC_RING_FLAG_AF_XDP_ZC,
> IGC_RING_FLAG_TX_HWTSTAMP,
> + IGC_RING_FLAG_RX_ALLOC_FAILED,
> };
>
> #define ring_uses_large_buffer(ring) \
> diff --git a/drivers/net/ethernet/intel/igc/igc_main.c
> b/drivers/net/ethernet/intel/igc/igc_main.c
> index 305e05294a26..e666739dfac7 100644
> --- a/drivers/net/ethernet/intel/igc/igc_main.c
> +++ b/drivers/net/ethernet/intel/igc/igc_main.c
> @@ -2192,6 +2192,7 @@ static bool igc_alloc_mapped_page(struct igc_ring
> *rx_ring,
> page = dev_alloc_pages(igc_rx_pg_order(rx_ring));
> if (unlikely(!page)) {
> rx_ring->rx_stats.alloc_failed++;
> + set_bit(IGC_RING_FLAG_RX_ALLOC_FAILED, _ring->flags);
> return false;
> }
>
> @@ -2208,6 +2209,7 @@ static bool igc_alloc_mapped_page(struct igc_ring
> *rx_ring,
> __free_page(page);
>
> rx_ring->rx_stats.alloc_failed++;
> + set_bit(IGC_RING_FLAG_RX_ALLOC_FAILED, _ring->flags);
> return false;
> }
>
> @@ -2659,6 +2661,7 @@ static int igc_clean_rx_irq(struct igc_q_vector
> *q_vector, const int budget)
> if (!skb) {
> rx_ring->rx_stats.alloc_failed++;
> rx_buffer->pagecnt_bias++;
> + set_bit(IGC_RING_FLAG_RX_ALLOC_FAILED, _ring->flags);
> break;
> }
>
> @@ -2739,6 +2742,7 @@ static void igc_dispatch_skb_zc(struct igc_q_vector
> *q_vector,
> skb = igc_construct_skb_zc(ring, xdp);
> if (!skb) {
> ring->rx_stats.alloc_failed++;
> + set_bit(IGC_RING_FLAG_RX_ALLOC_FAILED, >flags);
> return;
> }
>
> @@ -5811,11 +5815,23 @@ static void igc_watchdog_task(struct work_struct
> *work)
> if (adapter->flags & IGC_FLAG_HAS_MSIX) {
> u32 eics = 0;
>
> - for (i = 0; i < adapter->num_q_vectors; i++)
> - eics |= adapter->q_vector[i]->eims_value;
> - wr32(IGC_EICS, eics);
> + for (i = 0; i < adapter->num_q_vectors; i++) {
> + struct igc_ring *rx_ring = adapter->rx_ring[i];
> +
> + if (test_bit(IGC_RING_FLAG_RX_ALLOC_FAILED,
> _ring->flags)) {
Minor and optional: I guess you can replace test_bit() -> clear_bit()
with __test_and_clear_bit() here and below.
In any case:
Acked-by: Vinicius Costa Gomes
> + eics |= adapter->q_vector[i]->eims_value;
> + clear_bit(IGC_RING_FLAG_RX_ALLOC_FAILED,
> _ring->flags);
> + }
> + }
> + if (eics)
> + wr32(IGC_EICS, eics);
> } else {
> - wr32(IGC_ICS, IGC_ICS_RXDMT0);
> + struct igc_ring *rx_ring = adapter->rx_ring[0];
> +
> + if (test_bit(IGC_RING_FLAG_RX_ALLOC_FAILED, _ring->flags)) {
> + clear_bit(IGC_RING_FLAG_RX_ALLOC_FAILED,
> _ring->flags);
> + wr32(IGC_ICS, IGC_ICS_RXDMT0);
> + }
> }
>
> igc_ptp_tx_hang(adapter);
>
> ---
> base-commit: bb678f01804ccaa861b012b2b9426d69673d8a84
> change-id: 20240611-igc_irq-ccc1c8bc6890
>
> Best regards,
> --
> Kurt Kanzenbach
>
--
Vinicius
Re: [Intel-wired-lan] [PATCH iwl-next] igc: Get rid of spurious interrupts
On 2024-06-12 11:24:53 [+0200], Kurt Kanzenbach wrote: > When running the igc with XDP/ZC in busy polling mode with deferral of hard > interrupts, interrupts still happen from time to time. That is caused by > the igc task watchdog which triggers Rx interrupts periodically. > > That mechanism has been introduced to overcome skb/memory allocation > failures [1]. So the Rx clean functions stop processing the Rx ring in case > of such failure. The task watchdog triggers Rx interrupts periodically in > the hope that memory became available in the mean time. > > The current behavior is undesirable for real time applications, because the > driver induced Rx interrupts trigger also the softirq processing. However, > all real time packets should be processed by the application which uses the > busy polling method. > > Therefore, only trigger the Rx interrupts in case of real allocation > failures. Introduce a new flag for signaling that condition. > > [1] - > https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/?id=3be507547e6177e5c808544bd6a2efa2c7f1d436 > > Signed-off-by: Kurt Kanzenbach Reviewed-by: Sebastian Andrzej Siewior Sebastian
Re: [Intel-wired-lan] [PATCH iwl-next] igc: Get rid of spurious interrupts
On Wed, Jun 12, 2024 at 11:24:53AM +0200, Kurt Kanzenbach wrote:
> When running the igc with XDP/ZC in busy polling mode with deferral of hard
> interrupts, interrupts still happen from time to time. That is caused by
> the igc task watchdog which triggers Rx interrupts periodically.
>
> That mechanism has been introduced to overcome skb/memory allocation
> failures [1]. So the Rx clean functions stop processing the Rx ring in case
> of such failure. The task watchdog triggers Rx interrupts periodically in
> the hope that memory became available in the mean time.
>
> The current behavior is undesirable for real time applications, because the
> driver induced Rx interrupts trigger also the softirq processing. However,
> all real time packets should be processed by the application which uses the
> busy polling method.
>
> Therefore, only trigger the Rx interrupts in case of real allocation
> failures. Introduce a new flag for signaling that condition.
>
> [1] -
> https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/?id=3be507547e6177e5c808544bd6a2efa2c7f1d436
>
> Signed-off-by: Kurt Kanzenbach
Acked-by: Maciej Fijalkowski
> ---
> drivers/net/ethernet/intel/igc/igc.h | 1 +
> drivers/net/ethernet/intel/igc/igc_main.c | 24
> 2 files changed, 21 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/igc/igc.h
> b/drivers/net/ethernet/intel/igc/igc.h
> index 8b14c029eda1..7bfe5030e2c0 100644
> --- a/drivers/net/ethernet/intel/igc/igc.h
> +++ b/drivers/net/ethernet/intel/igc/igc.h
> @@ -682,6 +682,7 @@ enum igc_ring_flags_t {
> IGC_RING_FLAG_TX_DETECT_HANG,
> IGC_RING_FLAG_AF_XDP_ZC,
> IGC_RING_FLAG_TX_HWTSTAMP,
> + IGC_RING_FLAG_RX_ALLOC_FAILED,
> };
>
> #define ring_uses_large_buffer(ring) \
> diff --git a/drivers/net/ethernet/intel/igc/igc_main.c
> b/drivers/net/ethernet/intel/igc/igc_main.c
> index 305e05294a26..e666739dfac7 100644
> --- a/drivers/net/ethernet/intel/igc/igc_main.c
> +++ b/drivers/net/ethernet/intel/igc/igc_main.c
> @@ -2192,6 +2192,7 @@ static bool igc_alloc_mapped_page(struct igc_ring
> *rx_ring,
> page = dev_alloc_pages(igc_rx_pg_order(rx_ring));
> if (unlikely(!page)) {
> rx_ring->rx_stats.alloc_failed++;
> + set_bit(IGC_RING_FLAG_RX_ALLOC_FAILED, _ring->flags);
> return false;
> }
>
> @@ -2208,6 +2209,7 @@ static bool igc_alloc_mapped_page(struct igc_ring
> *rx_ring,
> __free_page(page);
>
> rx_ring->rx_stats.alloc_failed++;
> + set_bit(IGC_RING_FLAG_RX_ALLOC_FAILED, _ring->flags);
> return false;
> }
>
> @@ -2659,6 +2661,7 @@ static int igc_clean_rx_irq(struct igc_q_vector
> *q_vector, const int budget)
> if (!skb) {
> rx_ring->rx_stats.alloc_failed++;
> rx_buffer->pagecnt_bias++;
> + set_bit(IGC_RING_FLAG_RX_ALLOC_FAILED, _ring->flags);
> break;
> }
>
> @@ -2739,6 +2742,7 @@ static void igc_dispatch_skb_zc(struct igc_q_vector
> *q_vector,
> skb = igc_construct_skb_zc(ring, xdp);
> if (!skb) {
> ring->rx_stats.alloc_failed++;
> + set_bit(IGC_RING_FLAG_RX_ALLOC_FAILED, >flags);
> return;
> }
>
> @@ -5811,11 +5815,23 @@ static void igc_watchdog_task(struct work_struct
> *work)
> if (adapter->flags & IGC_FLAG_HAS_MSIX) {
> u32 eics = 0;
>
> - for (i = 0; i < adapter->num_q_vectors; i++)
> - eics |= adapter->q_vector[i]->eims_value;
> - wr32(IGC_EICS, eics);
> + for (i = 0; i < adapter->num_q_vectors; i++) {
> + struct igc_ring *rx_ring = adapter->rx_ring[i];
> +
> + if (test_bit(IGC_RING_FLAG_RX_ALLOC_FAILED,
> _ring->flags)) {
> + eics |= adapter->q_vector[i]->eims_value;
> + clear_bit(IGC_RING_FLAG_RX_ALLOC_FAILED,
> _ring->flags);
> + }
> + }
> + if (eics)
> + wr32(IGC_EICS, eics);
> } else {
> - wr32(IGC_ICS, IGC_ICS_RXDMT0);
> + struct igc_ring *rx_ring = adapter->rx_ring[0];
> +
> + if (test_bit(IGC_RING_FLAG_RX_ALLOC_FAILED, _ring->flags)) {
> + clear_bit(IGC_RING_FLAG_RX_ALLOC_FAILED,
> _ring->flags);
> + wr32(IGC_ICS, IGC_ICS_RXDMT0);
> + }
> }
>
> igc_ptp_tx_hang(adapter);
>
> ---
> base-commit: bb678f01804ccaa861b012b2b9426d69673d8a84
> change-id: 20240611-igc_irq-ccc1c8bc6890
>
> Best regards,
> --
> Kurt Kanzenbach
>
