From 415446185b939dcdcd6a483e705c805ab961e54c Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=C3=8D=C3=B1igo=20Huguet?= Date: Thu, 9 Sep 2021 11:28:45 +0200 Subject: [PATCH 1/2] sfc: fallback for lack of xdp tx queues MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit If there are not enough resources to allocate one TX queue per core for XDP TX it was completely disabled. This patch implements a fallback solution for sharing the available queues using __netif_tx_lock for synchronization. In the normal case that there is one TX queue per CPU, no locking is done, as it was before. With this fallback solution, XDP TX will work in much more cases that were failing, specially in machines with many CPUs. It's hard for XDP users to know what features are supported across different NICs and configurations, so they will benefit on having wider support. Signed-off-by: Íñigo Huguet Signed-off-by: David S. Miller --- drivers/net/ethernet/sfc/efx_channels.c | 54 ++++++++++++++++++++----- drivers/net/ethernet/sfc/net_driver.h | 8 ++++ drivers/net/ethernet/sfc/tx.c | 21 ++++++---- 3 files changed, 64 insertions(+), 19 deletions(-) diff --git a/drivers/net/ethernet/sfc/efx_channels.c b/drivers/net/ethernet/sfc/efx_channels.c index e5b0d795c301..e7849f1260a1 100644 --- a/drivers/net/ethernet/sfc/efx_channels.c +++ b/drivers/net/ethernet/sfc/efx_channels.c @@ -166,32 +166,46 @@ static int efx_allocate_msix_channels(struct efx_nic *efx, * We need a channel per event queue, plus a VI per tx queue. * This may be more pessimistic than it needs to be. */ - if (n_channels + n_xdp_ev > max_channels) { + if (n_channels >= max_channels) { + efx->xdp_txq_queues_mode = EFX_XDP_TX_QUEUES_DISABLED; 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; + "XDP_TX and XDP_REDIRECT will not work on this interface\n"); } else if (n_channels + n_xdp_tx > efx->max_vis) { + efx->xdp_txq_queues_mode = EFX_XDP_TX_QUEUES_DISABLED; 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; + "XDP_TX and XDP_REDIRECT will not work on this interface\n"); + } else if (n_channels + n_xdp_ev > max_channels) { + efx->xdp_txq_queues_mode = EFX_XDP_TX_QUEUES_SHARED; + netif_warn(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); + + n_xdp_ev = max_channels - n_channels; + netif_warn(efx, drv, efx->net_dev, + "XDP_TX and XDP_REDIRECT will work with reduced performance (%d cpus/tx_queue)\n", + DIV_ROUND_UP(n_xdp_tx, tx_per_ev * n_xdp_ev)); } else { + efx->xdp_txq_queues_mode = EFX_XDP_TX_QUEUES_DEDICATED; + } + + if (efx->xdp_txq_queues_mode != EFX_XDP_TX_QUEUES_DISABLED) { efx->n_xdp_channels = n_xdp_ev; 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, "Allocating %d TX and %d event queues for XDP\n", - n_xdp_tx, n_xdp_ev); + n_xdp_ev * tx_per_ev, n_xdp_ev); + } else { + efx->n_xdp_channels = 0; + efx->xdp_tx_per_channel = 0; + efx->xdp_tx_queue_count = 0; } if (vec_count < n_channels) { @@ -921,7 +935,25 @@ int efx_set_channels(struct efx_nic *efx) } } } - WARN_ON(xdp_queue_number != efx->xdp_tx_queue_count); + WARN_ON(efx->xdp_txq_queues_mode == EFX_XDP_TX_QUEUES_DEDICATED && + xdp_queue_number != efx->xdp_tx_queue_count); + WARN_ON(efx->xdp_txq_queues_mode != EFX_XDP_TX_QUEUES_DEDICATED && + xdp_queue_number > efx->xdp_tx_queue_count); + + /* If we have less XDP TX queues than CPUs, assign the already existing + * queues to the exceeding CPUs (this means that we will have to use + * locking when transmitting with XDP) + */ + next_queue = 0; + while (xdp_queue_number < efx->xdp_tx_queue_count) { + tx_queue = efx->xdp_tx_queues[next_queue++]; + channel = tx_queue->channel; + 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; + } rc = netif_set_real_num_tx_queues(efx->net_dev, efx->n_tx_channels); if (rc) diff --git a/drivers/net/ethernet/sfc/net_driver.h b/drivers/net/ethernet/sfc/net_driver.h index 9b4b25704271..e731c766f709 100644 --- a/drivers/net/ethernet/sfc/net_driver.h +++ b/drivers/net/ethernet/sfc/net_driver.h @@ -782,6 +782,12 @@ struct efx_async_filter_insertion { #define EFX_RPS_MAX_IN_FLIGHT 8 #endif /* CONFIG_RFS_ACCEL */ +enum efx_xdp_tx_queues_mode { + EFX_XDP_TX_QUEUES_DEDICATED, /* one queue per core, locking not needed */ + EFX_XDP_TX_QUEUES_SHARED, /* each queue used by more than 1 core */ + EFX_XDP_TX_QUEUES_DISABLED /* xdp tx not available */ +}; + /** * struct efx_nic - an Efx NIC * @name: Device name (net device name or bus id before net device registered) @@ -820,6 +826,7 @@ struct efx_async_filter_insertion { * should be allocated for this NIC * @xdp_tx_queue_count: Number of entries in %xdp_tx_queues. * @xdp_tx_queues: Array of pointers to tx queues used for XDP transmit. + * @xdp_txq_queues_mode: XDP TX queues sharing strategy. * @rxq_entries: Size of receive queues requested by user. * @txq_entries: Size of transmit queues requested by user. * @txq_stop_thresh: TX queue fill level at or above which we stop it. @@ -979,6 +986,7 @@ struct efx_nic { unsigned int xdp_tx_queue_count; struct efx_tx_queue **xdp_tx_queues; + enum efx_xdp_tx_queues_mode xdp_txq_queues_mode; unsigned rxq_entries; unsigned txq_entries; diff --git a/drivers/net/ethernet/sfc/tx.c b/drivers/net/ethernet/sfc/tx.c index 0c6650d2e239..c7afd6cda902 100644 --- a/drivers/net/ethernet/sfc/tx.c +++ b/drivers/net/ethernet/sfc/tx.c @@ -430,21 +430,23 @@ int efx_xdp_tx_buffers(struct efx_nic *efx, int n, struct xdp_frame **xdpfs, int cpu; int i; - cpu = raw_smp_processor_id(); + if (unlikely(efx->xdp_txq_queues_mode == EFX_XDP_TX_QUEUES_DISABLED)) + return -EINVAL; + if (unlikely(n && !xdpfs)) + return -EINVAL; + if (unlikely(!n)) + return 0; - if (!efx->xdp_tx_queue_count || - unlikely(cpu >= efx->xdp_tx_queue_count)) + cpu = raw_smp_processor_id(); + if (unlikely(cpu >= efx->xdp_tx_queue_count)) return -EINVAL; tx_queue = efx->xdp_tx_queues[cpu]; if (unlikely(!tx_queue)) return -EINVAL; - if (unlikely(n && !xdpfs)) - return -EINVAL; - - if (!n) - return 0; + if (efx->xdp_txq_queues_mode != EFX_XDP_TX_QUEUES_DEDICATED) + HARD_TX_LOCK(efx->net_dev, tx_queue->core_txq, cpu); /* Check for available space. We should never need multiple * descriptors per frame. @@ -484,6 +486,9 @@ int efx_xdp_tx_buffers(struct efx_nic *efx, int n, struct xdp_frame **xdpfs, if (flush && i > 0) efx_nic_push_buffers(tx_queue); + if (efx->xdp_txq_queues_mode != EFX_XDP_TX_QUEUES_DEDICATED) + HARD_TX_UNLOCK(efx->net_dev, tx_queue->core_txq); + return i == 0 ? -EIO : i; } From 6215b608a8c4d4a478721e14a6faa0dc56e4a693 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=C3=8D=C3=B1igo=20Huguet?= Date: Thu, 9 Sep 2021 11:28:46 +0200 Subject: [PATCH 2/2] sfc: last resort fallback for lack of xdp tx queues MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Previous patch addressed the situation of having some free resources for xdp tx but not enough for one tx queue per CPU. This patch address the worst case of not having resources at all for xdp tx. Instead of using queues dedicated to xdp, normal queues used by network stack are shared for both cases, using __netif_tx_lock for synchronization. Also queue stop/restart must be considered in the xdp path to avoid freezing the queue. This is not the ideal situation we might want to be, and a performance penalty is expected both for normal and xdp traffic, but at least XDP will work in all possible situations (with a warning in the logs), improving a bit the pain of not knowing in what situations we can use it and in what situations we cannot. Signed-off-by: Íñigo Huguet Signed-off-by: David S. Miller --- drivers/net/ethernet/sfc/efx_channels.c | 82 ++++++++++++++----------- drivers/net/ethernet/sfc/net_driver.h | 2 +- drivers/net/ethernet/sfc/tx.c | 14 ++++- 3 files changed, 58 insertions(+), 40 deletions(-) diff --git a/drivers/net/ethernet/sfc/efx_channels.c b/drivers/net/ethernet/sfc/efx_channels.c index e7849f1260a1..3dbea028b325 100644 --- a/drivers/net/ethernet/sfc/efx_channels.c +++ b/drivers/net/ethernet/sfc/efx_channels.c @@ -167,19 +167,19 @@ static int efx_allocate_msix_channels(struct efx_nic *efx, * This may be more pessimistic than it needs to be. */ if (n_channels >= max_channels) { - efx->xdp_txq_queues_mode = EFX_XDP_TX_QUEUES_DISABLED; - 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\n"); + efx->xdp_txq_queues_mode = EFX_XDP_TX_QUEUES_BORROWED; + netif_warn(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_warn(efx, drv, efx->net_dev, + "XDP_TX and XDP_REDIRECT might decrease device's performance\n"); } else if (n_channels + n_xdp_tx > efx->max_vis) { - efx->xdp_txq_queues_mode = EFX_XDP_TX_QUEUES_DISABLED; - 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\n"); + efx->xdp_txq_queues_mode = EFX_XDP_TX_QUEUES_BORROWED; + netif_warn(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_warn(efx, drv, efx->net_dev, + "XDP_TX and XDP_REDIRECT might decrease device's performance\n"); } else if (n_channels + n_xdp_ev > max_channels) { efx->xdp_txq_queues_mode = EFX_XDP_TX_QUEUES_SHARED; netif_warn(efx, drv, efx->net_dev, @@ -194,7 +194,7 @@ static int efx_allocate_msix_channels(struct efx_nic *efx, efx->xdp_txq_queues_mode = EFX_XDP_TX_QUEUES_DEDICATED; } - if (efx->xdp_txq_queues_mode != EFX_XDP_TX_QUEUES_DISABLED) { + if (efx->xdp_txq_queues_mode != EFX_XDP_TX_QUEUES_BORROWED) { efx->n_xdp_channels = n_xdp_ev; efx->xdp_tx_per_channel = tx_per_ev; efx->xdp_tx_queue_count = n_xdp_tx; @@ -205,7 +205,7 @@ static int efx_allocate_msix_channels(struct efx_nic *efx, } else { efx->n_xdp_channels = 0; efx->xdp_tx_per_channel = 0; - efx->xdp_tx_queue_count = 0; + efx->xdp_tx_queue_count = n_xdp_tx; } if (vec_count < n_channels) { @@ -872,6 +872,20 @@ rollback: goto out; } +static inline int +efx_set_xdp_tx_queue(struct efx_nic *efx, int xdp_queue_number, + struct efx_tx_queue *tx_queue) +{ + if (xdp_queue_number >= efx->xdp_tx_queue_count) + return -EINVAL; + + netif_dbg(efx, drv, efx->net_dev, "Channel %u TXQ %u is XDP %u, HW %u\n", + tx_queue->channel->channel, tx_queue->label, + xdp_queue_number, tx_queue->queue); + efx->xdp_tx_queues[xdp_queue_number] = tx_queue; + return 0; +} + int efx_set_channels(struct efx_nic *efx) { struct efx_tx_queue *tx_queue; @@ -910,20 +924,9 @@ 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++; - - /* 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) { - 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; + rc = efx_set_xdp_tx_queue(efx, xdp_queue_number, tx_queue); + if (rc == 0) xdp_queue_number++; - } } } else { efx_for_each_channel_tx_queue(tx_queue, channel) { @@ -932,6 +935,17 @@ int efx_set_channels(struct efx_nic *efx) channel->channel, tx_queue->label, tx_queue->queue); } + + /* If XDP is borrowing queues from net stack, it must use the queue + * with no csum offload, which is the first one of the channel + * (note: channel->tx_queue_by_type is not initialized yet) + */ + if (efx->xdp_txq_queues_mode == EFX_XDP_TX_QUEUES_BORROWED) { + tx_queue = &channel->tx_queue[0]; + rc = efx_set_xdp_tx_queue(efx, xdp_queue_number, tx_queue); + if (rc == 0) + xdp_queue_number++; + } } } } @@ -940,19 +954,15 @@ int efx_set_channels(struct efx_nic *efx) WARN_ON(efx->xdp_txq_queues_mode != EFX_XDP_TX_QUEUES_DEDICATED && xdp_queue_number > efx->xdp_tx_queue_count); - /* If we have less XDP TX queues than CPUs, assign the already existing - * queues to the exceeding CPUs (this means that we will have to use - * locking when transmitting with XDP) + /* If we have more CPUs than assigned XDP TX queues, assign the already + * existing queues to the exceeding CPUs */ next_queue = 0; while (xdp_queue_number < efx->xdp_tx_queue_count) { tx_queue = efx->xdp_tx_queues[next_queue++]; - channel = tx_queue->channel; - 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; + rc = efx_set_xdp_tx_queue(efx, xdp_queue_number, tx_queue); + if (rc == 0) + xdp_queue_number++; } rc = netif_set_real_num_tx_queues(efx->net_dev, efx->n_tx_channels); diff --git a/drivers/net/ethernet/sfc/net_driver.h b/drivers/net/ethernet/sfc/net_driver.h index e731c766f709..f6981810039d 100644 --- a/drivers/net/ethernet/sfc/net_driver.h +++ b/drivers/net/ethernet/sfc/net_driver.h @@ -785,7 +785,7 @@ struct efx_async_filter_insertion { enum efx_xdp_tx_queues_mode { EFX_XDP_TX_QUEUES_DEDICATED, /* one queue per core, locking not needed */ EFX_XDP_TX_QUEUES_SHARED, /* each queue used by more than 1 core */ - EFX_XDP_TX_QUEUES_DISABLED /* xdp tx not available */ + EFX_XDP_TX_QUEUES_BORROWED /* queues borrowed from net stack */ }; /** diff --git a/drivers/net/ethernet/sfc/tx.c b/drivers/net/ethernet/sfc/tx.c index c7afd6cda902..d16e031e95f4 100644 --- a/drivers/net/ethernet/sfc/tx.c +++ b/drivers/net/ethernet/sfc/tx.c @@ -428,10 +428,8 @@ int efx_xdp_tx_buffers(struct efx_nic *efx, int n, struct xdp_frame **xdpfs, unsigned int len; int space; int cpu; - int i; + int i = 0; - if (unlikely(efx->xdp_txq_queues_mode == EFX_XDP_TX_QUEUES_DISABLED)) - return -EINVAL; if (unlikely(n && !xdpfs)) return -EINVAL; if (unlikely(!n)) @@ -448,6 +446,15 @@ int efx_xdp_tx_buffers(struct efx_nic *efx, int n, struct xdp_frame **xdpfs, if (efx->xdp_txq_queues_mode != EFX_XDP_TX_QUEUES_DEDICATED) HARD_TX_LOCK(efx->net_dev, tx_queue->core_txq, cpu); + /* If we're borrowing net stack queues we have to handle stop-restart + * or we might block the queue and it will be considered as frozen + */ + if (efx->xdp_txq_queues_mode == EFX_XDP_TX_QUEUES_BORROWED) { + if (netif_tx_queue_stopped(tx_queue->core_txq)) + goto unlock; + efx_tx_maybe_stop_queue(tx_queue); + } + /* Check for available space. We should never need multiple * descriptors per frame. */ @@ -486,6 +493,7 @@ int efx_xdp_tx_buffers(struct efx_nic *efx, int n, struct xdp_frame **xdpfs, if (flush && i > 0) efx_nic_push_buffers(tx_queue); +unlock: if (efx->xdp_txq_queues_mode != EFX_XDP_TX_QUEUES_DEDICATED) HARD_TX_UNLOCK(efx->net_dev, tx_queue->core_txq);