From f28100cb9c9645c07cbd22431278ac9492f6a01c Mon Sep 17 00:00:00 2001 From: Íñigo Huguet Date: Tue, 13 Jul 2021 16:21:27 +0200 Subject: sfc: fix lack of XDP TX queues - error XDP TX failed (-22) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Fixes: e26ca4b53582 sfc: reduce the number of requested xdp ev queues The buggy commit intended to allocate less channels for XDP in order to be more unlikely to reach the limit of 32 channels of the driver. The idea was to use each IRQ/eventqeue for more XDP TX queues than before, calculating which is the maximum number of TX queues that one event queue can handle. For example, in EF10 each event queue could handle up to 8 queues, better than the 4 they were handling before the change. This way, it would have to allocate half of channels than before for XDP TX. The problem is that the TX queues are also contained inside the channel structs, and there are only 4 queues per channel. Reducing the number of channels means also reducing the number of queues, resulting in not having the desired number of 1 queue per CPU. This leads to getting errors on XDP_TX and XDP_REDIRECT if they're executed from a high numbered CPU, because there only exist queues for the low half of CPUs, actually. If XDP_TX/REDIRECT is executed in a low numbered CPU, the error doesn't happen. This is the error in the logs (repeated many times, even rate limited): sfc 0000:5e:00.0 ens3f0np0: XDP TX failed (-22) This errors happens in function efx_xdp_tx_buffers, where it expects to have a dedicated XDP TX queue per CPU. Reverting the change makes again more likely to reach the limit of 32 channels in machines with many CPUs. If this happen, no XDP_TX/REDIRECT will be possible at all, and we will have this log error messages: At interface probe: sfc 0000:5e:00.0: Insufficient resources for 12 XDP event queues (24 other channels, max 32) At every subsequent XDP_TX/REDIRECT failure, rate limited: sfc 0000:5e:00.0 ens3f0np0: XDP TX failed (-22) However, without reverting the change, it makes the user to think that everything is OK at probe time, but later it fails in an unpredictable way, depending on the CPU that handles the packet. It is better to restore the predictable behaviour. If the user sees the error message at probe time, he/she can try to configure the best way it fits his/her needs. At least, he/she will have 2 options: - Accept that XDP_TX/REDIRECT is not available (he/she may not need it) - Load sfc module with modparam 'rss_cpus' with a lower number, thus creating less normal RX queues/channels, letting more free resources for XDP, with some performance penalty. Anyway, let the calculation of maximum TX queues that can be handled by a single event queue, and use it only if it's less than the number of TX queues per channel. This doesn't happen in practice, but could happen if some constant values are tweaked in the future, such us EFX_MAX_TXQ_PER_CHANNEL, EFX_MAX_EVQ_SIZE or EFX_MAX_DMAQ_SIZE. Related mailing list thread: https://lore.kernel.org/bpf/20201215104327.2be76156@carbon/ Signed-off-by: Íñigo Huguet Signed-off-by: David S. Miller --- drivers/net/ethernet/sfc/efx_channels.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'drivers/net/ethernet/sfc') diff --git a/drivers/net/ethernet/sfc/efx_channels.c b/drivers/net/ethernet/sfc/efx_channels.c index a3ca406a3561..5b71f8a03a6d 100644 --- a/drivers/net/ethernet/sfc/efx_channels.c +++ b/drivers/net/ethernet/sfc/efx_channels.c @@ -152,6 +152,7 @@ static int efx_allocate_msix_channels(struct efx_nic *efx, * maximum size. */ tx_per_ev = EFX_MAX_EVQ_SIZE / EFX_TXQ_MAX_ENT(efx); + tx_per_ev = min(tx_per_ev, EFX_MAX_TXQ_PER_CHANNEL); n_xdp_tx = num_possible_cpus(); n_xdp_ev = DIV_ROUND_UP(n_xdp_tx, tx_per_ev); @@ -181,7 +182,7 @@ static int efx_allocate_msix_channels(struct efx_nic *efx, efx->xdp_tx_queue_count = 0; } else { efx->n_xdp_channels = n_xdp_ev; - efx->xdp_tx_per_channel = EFX_MAX_TXQ_PER_CHANNEL; + efx->xdp_tx_per_channel = tx_per_ev; efx->xdp_tx_queue_count = n_xdp_tx; n_channels += n_xdp_ev; netif_dbg(efx, drv, efx->net_dev, -- cgit v1.2.3 From 788bc000d4c2f25232db19ab3a0add0ba4e27671 Mon Sep 17 00:00:00 2001 From: Íñigo Huguet Date: Tue, 13 Jul 2021 16:21:28 +0200 Subject: sfc: ensure correct number of XDP queues MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Commit 99ba0ea616aa ("sfc: adjust efx->xdp_tx_queue_count with the real number of initialized queues") intended to fix a problem caused by a round up when calculating the number of XDP channels and queues. However, this was not the real problem. The real problem was that the number of XDP TX queues had been reduced to half in commit e26ca4b53582 ("sfc: reduce the number of requested xdp ev queues"), but the variable xdp_tx_queue_count had remained the same. Once the correct number of XDP TX queues is created again in the previous patch of this series, this also can be reverted since the error doesn't actually exist. Only in the case that there is a bug in the code we can have different values in xdp_queue_number and efx->xdp_tx_queue_count. Because of this, and per Edward Cree's suggestion, I add instead a WARN_ON to catch if it happens again in the future. Note that the number of allocated queues can be higher than the number of used ones due to the round up, as explained in the existing comment in the code. That's why we also have to stop increasing xdp_queue_number beyond efx->xdp_tx_queue_count. Signed-off-by: Íñigo Huguet Signed-off-by: David S. Miller --- drivers/net/ethernet/sfc/efx_channels.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) (limited to 'drivers/net/ethernet/sfc') diff --git a/drivers/net/ethernet/sfc/efx_channels.c b/drivers/net/ethernet/sfc/efx_channels.c index 5b71f8a03a6d..bb48a139dd15 100644 --- a/drivers/net/ethernet/sfc/efx_channels.c +++ b/drivers/net/ethernet/sfc/efx_channels.c @@ -892,18 +892,20 @@ int efx_set_channels(struct efx_nic *efx) if (efx_channel_is_xdp_tx(channel)) { efx_for_each_channel_tx_queue(tx_queue, channel) { tx_queue->queue = next_queue++; - netif_dbg(efx, drv, efx->net_dev, "Channel %u TXQ %u is XDP %u, HW %u\n", - channel->channel, tx_queue->label, - xdp_queue_number, tx_queue->queue); + /* We may have a few left-over XDP TX * queues owing to xdp_tx_queue_count * not dividing evenly by EFX_MAX_TXQ_PER_CHANNEL. * We still allocate and probe those * TXQs, but never use them. */ - if (xdp_queue_number < efx->xdp_tx_queue_count) + if (xdp_queue_number < efx->xdp_tx_queue_count) { + netif_dbg(efx, drv, efx->net_dev, "Channel %u TXQ %u is XDP %u, HW %u\n", + channel->channel, tx_queue->label, + xdp_queue_number, tx_queue->queue); efx->xdp_tx_queues[xdp_queue_number] = tx_queue; - xdp_queue_number++; + xdp_queue_number++; + } } } else { efx_for_each_channel_tx_queue(tx_queue, channel) { @@ -915,8 +917,7 @@ int efx_set_channels(struct efx_nic *efx) } } } - if (xdp_queue_number) - efx->xdp_tx_queue_count = xdp_queue_number; + WARN_ON(xdp_queue_number != efx->xdp_tx_queue_count); rc = netif_set_real_num_tx_queues(efx->net_dev, efx->n_tx_channels); if (rc) -- cgit v1.2.3 From d2a16bde77322fca6b6f36ebe19097a1c3c46f74 Mon Sep 17 00:00:00 2001 From: Íñigo Huguet Date: Tue, 13 Jul 2021 16:21:29 +0200 Subject: sfc: add logs explaining XDP_TX/REDIRECT is not available MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit If it's not possible to allocate enough channels for XDP, XDP_TX and XDP_REDIRECT don't work. However, only a message saying that not enough channels were available was shown, but not saying what are the consequences in that case. The user didn't know if he/she can use XDP or not, if the performance is reduced, or what. Signed-off-by: Íñigo Huguet Signed-off-by: David S. Miller --- drivers/net/ethernet/sfc/efx_channels.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'drivers/net/ethernet/sfc') diff --git a/drivers/net/ethernet/sfc/efx_channels.c b/drivers/net/ethernet/sfc/efx_channels.c index bb48a139dd15..e5b0d795c301 100644 --- a/drivers/net/ethernet/sfc/efx_channels.c +++ b/drivers/net/ethernet/sfc/efx_channels.c @@ -170,6 +170,8 @@ static int efx_allocate_msix_channels(struct efx_nic *efx, netif_err(efx, drv, efx->net_dev, "Insufficient resources for %d XDP event queues (%d other channels, max %d)\n", n_xdp_ev, n_channels, max_channels); + netif_err(efx, drv, efx->net_dev, + "XDP_TX and XDP_REDIRECT will not work on this interface"); efx->n_xdp_channels = 0; efx->xdp_tx_per_channel = 0; efx->xdp_tx_queue_count = 0; @@ -177,6 +179,8 @@ static int efx_allocate_msix_channels(struct efx_nic *efx, netif_err(efx, drv, efx->net_dev, "Insufficient resources for %d XDP TX queues (%d other channels, max VIs %d)\n", n_xdp_tx, n_channels, efx->max_vis); + netif_err(efx, drv, efx->net_dev, + "XDP_TX and XDP_REDIRECT will not work on this interface"); efx->n_xdp_channels = 0; efx->xdp_tx_per_channel = 0; efx->xdp_tx_queue_count = 0; -- cgit v1.2.3