[PATCH net-next 0/2] net: mana: Avoid queue struct allocation failure under memory fragmentation

[PATCH net-next 0/2] net: mana: Avoid queue struct allocation failure under memory fragmentation

[Aditya Garg]

The MANA driver can fail to load on systems with high memory
utilization because several allocations in the queue setup paths
require large physically contiguous blocks via kmalloc. Under memory
fragmentation these high-order allocations may fail, preventing the
driver from creating queues at probe time or when reconfiguring
channels, ring parameters or MTU at runtime.

Allocation sizes that are problematic:

  mana_create_txq -> tx_qp flat array (sizeof(mana_tx_qp) = 35528):
    16 queues (default): 35528 * 16 =  ~555 KB contiguous
    64 queues (max):     35528 * 64 = ~2220 KB contiguous

  mana_create_rxq -> rxq struct with flex array
  (sizeof(mana_rxq) = 35712, rx_oobs=296 per entry):
    depth 1024 (default): 35712 + 296 * 1024 =  ~331 KB per queue
    depth 8192 (max):     35712 + 296 * 8192 = ~2403 KB per queue

  mana_pre_alloc_rxbufs -> rxbufs_pre and das_pre arrays:
    16 queues, depth 1024 (default): 16 * 1024 * 8 =  128 KB each
    64 queues, depth 8192 (max):     64 * 8192 * 8 = 4096 KB each

This series addresses the issue by:
  1. Converting the tx_qp flat array into an array of pointers with
     per-queue kvzalloc (~35 KB each), replacing a single contiguous
     allocation that can reach ~2.2 MB at 64 queues.
  2. Switching rxbufs_pre, das_pre, and rxq allocations to
     kvmalloc/kvzalloc so the allocator can fall back to vmalloc
     when contiguous memory is unavailable.

Throughput testing confirms no regression. Since kvmalloc falls
back to vmalloc under memory fragmentation, all kvmalloc calls
were temporarily replaced with vmalloc to simulate the fallback
path (iperf3, GBits/sec):

                 Physically contiguous         vmalloc region
  Connections      TX          RX              TX          RX
  --------------------------------------------------------------
  1                47.2        46.9            46.8        46.6
  16               181         181             181         181
  32               181         181             181         181
  64               181         181             181         181

Aditya Garg (2):
  net: mana: Use per-queue allocation for tx_qp to reduce allocation
    size
  net: mana: Use kvmalloc for large RX queue and buffer allocations

 .../net/ethernet/microsoft/mana/mana_bpf.c    |  2 +-
 drivers/net/ethernet/microsoft/mana/mana_en.c | 61 +++++++++++--------
 .../ethernet/microsoft/mana/mana_ethtool.c    |  2 +-
 include/net/mana/mana.h                       |  2 +-
 4 files changed, 39 insertions(+), 28 deletions(-)

-- 
2.43.0

[PATCH net-next 1/2] net: mana: Use per-queue allocation for tx_qp to reduce allocation size

[Aditya Garg]

Convert tx_qp from a single contiguous array allocation to per-queue
individual allocations. Each mana_tx_qp struct is approximately 35KB.
With many queues (e.g., 32/64), the flat array requires a single
contiguous allocation that can fail under memory fragmentation.

Change mana_tx_qp *tx_qp to mana_tx_qp **tx_qp (array of pointers),
allocating each queue's mana_tx_qp individually via kvzalloc. This
reduces each allocation to ~35KB and provides vmalloc fallback,
avoiding allocation failure due to fragmentation.

Signed-off-by: Aditya Garg <gargaditya@linux.microsoft.com>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
---
 .../net/ethernet/microsoft/mana/mana_bpf.c    |  2 +-
 drivers/net/ethernet/microsoft/mana/mana_en.c | 49 ++++++++++++-------
 .../ethernet/microsoft/mana/mana_ethtool.c    |  2 +-
 include/net/mana/mana.h                       |  2 +-
 4 files changed, 33 insertions(+), 22 deletions(-)

diff --git a/drivers/net/ethernet/microsoft/mana/mana_bpf.c b/drivers/net/ethernet/microsoft/mana/mana_bpf.c
index 7697c9b52ed3..b5e9bb184a1d 100644
--- a/drivers/net/ethernet/microsoft/mana/mana_bpf.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_bpf.c
@@ -68,7 +68,7 @@ int mana_xdp_xmit(struct net_device *ndev, int n, struct xdp_frame **frames,
 		count++;
 	}
 
-	tx_stats = &apc->tx_qp[q_idx].txq.stats;
+	tx_stats = &apc->tx_qp[q_idx]->txq.stats;
 
 	u64_stats_update_begin(&tx_stats->syncp);
 	tx_stats->xdp_xmit += count;
diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
index 09a53c977545..49ee77b0939a 100644
--- a/drivers/net/ethernet/microsoft/mana/mana_en.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
@@ -355,9 +355,9 @@ netdev_tx_t mana_start_xmit(struct sk_buff *skb, struct net_device *ndev)
 	if (skb_cow_head(skb, MANA_HEADROOM))
 		goto tx_drop_count;
 
-	txq = &apc->tx_qp[txq_idx].txq;
+	txq = &apc->tx_qp[txq_idx]->txq;
 	gdma_sq = txq->gdma_sq;
-	cq = &apc->tx_qp[txq_idx].tx_cq;
+	cq = &apc->tx_qp[txq_idx]->tx_cq;
 	tx_stats = &txq->stats;
 
 	BUILD_BUG_ON(MAX_TX_WQE_SGL_ENTRIES != MANA_MAX_TX_WQE_SGL_ENTRIES);
@@ -614,7 +614,7 @@ static void mana_get_stats64(struct net_device *ndev,
 	}
 
 	for (q = 0; q < num_queues; q++) {
-		tx_stats = &apc->tx_qp[q].txq.stats;
+		tx_stats = &apc->tx_qp[q]->txq.stats;
 
 		do {
 			start = u64_stats_fetch_begin(&tx_stats->syncp);
@@ -2284,21 +2284,26 @@ static void mana_destroy_txq(struct mana_port_context *apc)
 		return;
 
 	for (i = 0; i < apc->num_queues; i++) {
-		debugfs_remove_recursive(apc->tx_qp[i].mana_tx_debugfs);
-		apc->tx_qp[i].mana_tx_debugfs = NULL;
+		if (!apc->tx_qp[i])
+			continue;
+
+		debugfs_remove_recursive(apc->tx_qp[i]->mana_tx_debugfs);
+		apc->tx_qp[i]->mana_tx_debugfs = NULL;
 
-		napi = &apc->tx_qp[i].tx_cq.napi;
-		if (apc->tx_qp[i].txq.napi_initialized) {
+		napi = &apc->tx_qp[i]->tx_cq.napi;
+		if (apc->tx_qp[i]->txq.napi_initialized) {
 			napi_synchronize(napi);
 			napi_disable_locked(napi);
 			netif_napi_del_locked(napi);
-			apc->tx_qp[i].txq.napi_initialized = false;
+			apc->tx_qp[i]->txq.napi_initialized = false;
 		}
-		mana_destroy_wq_obj(apc, GDMA_SQ, apc->tx_qp[i].tx_object);
+		mana_destroy_wq_obj(apc, GDMA_SQ, apc->tx_qp[i]->tx_object);
 
-		mana_deinit_cq(apc, &apc->tx_qp[i].tx_cq);
+		mana_deinit_cq(apc, &apc->tx_qp[i]->tx_cq);
 
-		mana_deinit_txq(apc, &apc->tx_qp[i].txq);
+		mana_deinit_txq(apc, &apc->tx_qp[i]->txq);
+
+		kvfree(apc->tx_qp[i]);
 	}
 
 	kfree(apc->tx_qp);
@@ -2307,7 +2312,7 @@ static void mana_destroy_txq(struct mana_port_context *apc)
 
 static void mana_create_txq_debugfs(struct mana_port_context *apc, int idx)
 {
-	struct mana_tx_qp *tx_qp = &apc->tx_qp[idx];
+	struct mana_tx_qp *tx_qp = apc->tx_qp[idx];
 	char qnum[32];
 
 	sprintf(qnum, "TX-%d", idx);
@@ -2346,7 +2351,7 @@ static int mana_create_txq(struct mana_port_context *apc,
 	int err;
 	int i;
 
-	apc->tx_qp = kzalloc_objs(struct mana_tx_qp, apc->num_queues);
+	apc->tx_qp = kzalloc_objs(struct mana_tx_qp *, apc->num_queues);
 	if (!apc->tx_qp)
 		return -ENOMEM;
 
@@ -2366,10 +2371,16 @@ static int mana_create_txq(struct mana_port_context *apc,
 	gc = gd->gdma_context;
 
 	for (i = 0; i < apc->num_queues; i++) {
-		apc->tx_qp[i].tx_object = INVALID_MANA_HANDLE;
+		apc->tx_qp[i] = kvzalloc_obj(*apc->tx_qp[i]);
+		if (!apc->tx_qp[i]) {
+			err = -ENOMEM;
+			goto out;
+		}
+
+		apc->tx_qp[i]->tx_object = INVALID_MANA_HANDLE;
 
 		/* Create SQ */
-		txq = &apc->tx_qp[i].txq;
+		txq = &apc->tx_qp[i]->txq;
 
 		u64_stats_init(&txq->stats.syncp);
 		txq->ndev = net;
@@ -2387,7 +2398,7 @@ static int mana_create_txq(struct mana_port_context *apc,
 			goto out;
 
 		/* Create SQ's CQ */
-		cq = &apc->tx_qp[i].tx_cq;
+		cq = &apc->tx_qp[i]->tx_cq;
 		cq->type = MANA_CQ_TYPE_TX;
 
 		cq->txq = txq;
@@ -2416,7 +2427,7 @@ static int mana_create_txq(struct mana_port_context *apc,
 
 		err = mana_create_wq_obj(apc, apc->port_handle, GDMA_SQ,
 					 &wq_spec, &cq_spec,
-					 &apc->tx_qp[i].tx_object);
+					 &apc->tx_qp[i]->tx_object);
 
 		if (err)
 			goto out;
@@ -3242,7 +3253,7 @@ static int mana_dealloc_queues(struct net_device *ndev)
 	 */
 
 	for (i = 0; i < apc->num_queues; i++) {
-		txq = &apc->tx_qp[i].txq;
+		txq = &apc->tx_qp[i]->txq;
 		tsleep = 1000;
 		while (atomic_read(&txq->pending_sends) > 0 &&
 		       time_before(jiffies, timeout)) {
@@ -3261,7 +3272,7 @@ static int mana_dealloc_queues(struct net_device *ndev)
 	}
 
 	for (i = 0; i < apc->num_queues; i++) {
-		txq = &apc->tx_qp[i].txq;
+		txq = &apc->tx_qp[i]->txq;
 		while ((skb = skb_dequeue(&txq->pending_skbs))) {
 			mana_unmap_skb(skb, apc);
 			dev_kfree_skb_any(skb);
diff --git a/drivers/net/ethernet/microsoft/mana/mana_ethtool.c b/drivers/net/ethernet/microsoft/mana/mana_ethtool.c
index f2d220b371b5..f5901e4c9816 100644
--- a/drivers/net/ethernet/microsoft/mana/mana_ethtool.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_ethtool.c
@@ -251,7 +251,7 @@ static void mana_get_ethtool_stats(struct net_device *ndev,
 	}
 
 	for (q = 0; q < num_queues; q++) {
-		tx_stats = &apc->tx_qp[q].txq.stats;
+		tx_stats = &apc->tx_qp[q]->txq.stats;
 
 		do {
 			start = u64_stats_fetch_begin(&tx_stats->syncp);
diff --git a/include/net/mana/mana.h b/include/net/mana/mana.h
index a078af283bdd..60b4a4146ea2 100644
--- a/include/net/mana/mana.h
+++ b/include/net/mana/mana.h
@@ -505,7 +505,7 @@ struct mana_port_context {
 	bool tx_shortform_allowed;
 	u16 tx_vp_offset;
 
-	struct mana_tx_qp *tx_qp;
+	struct mana_tx_qp **tx_qp;
 
 	/* Indirection Table for RX & TX. The values are queue indexes */
 	u32 *indir_table;
-- 
2.43.0

[PATCH net-next 2/2] net: mana: Use kvmalloc for large RX queue and buffer allocations

[Aditya Garg]

The RX path allocations for rxbufs_pre, das_pre, and rxq scale with
queue count and queue depth. With high queue counts and depth, these can
exceed what kmalloc can reliably provide from physically contiguous
memory under fragmentation.

Switch these from kmalloc to kvmalloc variants so the allocator
transparently falls back to vmalloc when contiguous memory is scarce,
and update the corresponding frees to kvfree.

Signed-off-by: Aditya Garg <gargaditya@linux.microsoft.com>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
---
 drivers/net/ethernet/microsoft/mana/mana_en.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
index 49ee77b0939a..585d891bbbac 100644
--- a/drivers/net/ethernet/microsoft/mana/mana_en.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
@@ -685,11 +685,11 @@ void mana_pre_dealloc_rxbufs(struct mana_port_context *mpc)
 		put_page(virt_to_head_page(mpc->rxbufs_pre[i]));
 	}
 
-	kfree(mpc->das_pre);
+	kvfree(mpc->das_pre);
 	mpc->das_pre = NULL;
 
 out2:
-	kfree(mpc->rxbufs_pre);
+	kvfree(mpc->rxbufs_pre);
 	mpc->rxbufs_pre = NULL;
 
 out1:
@@ -806,11 +806,11 @@ int mana_pre_alloc_rxbufs(struct mana_port_context *mpc, int new_mtu, int num_qu
 	num_rxb = num_queues * mpc->rx_queue_size;
 
 	WARN(mpc->rxbufs_pre, "mana rxbufs_pre exists\n");
-	mpc->rxbufs_pre = kmalloc_array(num_rxb, sizeof(void *), GFP_KERNEL);
+	mpc->rxbufs_pre = kvmalloc_array(num_rxb, sizeof(void *), GFP_KERNEL);
 	if (!mpc->rxbufs_pre)
 		goto error;
 
-	mpc->das_pre = kmalloc_objs(dma_addr_t, num_rxb);
+	mpc->das_pre = kvmalloc_objs(dma_addr_t, num_rxb);
 	if (!mpc->das_pre)
 		goto error;
 
@@ -2527,7 +2527,7 @@ static void mana_destroy_rxq(struct mana_port_context *apc,
 	if (rxq->gdma_rq)
 		mana_gd_destroy_queue(gc, rxq->gdma_rq);
 
-	kfree(rxq);
+	kvfree(rxq);
 }
 
 static int mana_fill_rx_oob(struct mana_recv_buf_oob *rx_oob, u32 mem_key,
@@ -2667,7 +2667,7 @@ static struct mana_rxq *mana_create_rxq(struct mana_port_context *apc,
 
 	gc = gd->gdma_context;
 
-	rxq = kzalloc_flex(*rxq, rx_oobs, apc->rx_queue_size);
+	rxq = kvzalloc_flex(*rxq, rx_oobs, apc->rx_queue_size);
 	if (!rxq)
 		return NULL;
 
-- 
2.43.0

Re: [PATCH net-next 0/2] net: mana: Avoid queue struct allocation failure under memory fragmentation

[Jakub Kicinski]

On Tue, 14 Apr 2026 08:13:28 -0700 Aditya Garg wrote:
> The MANA driver can fail to load on systems with high memory
> utilization because several allocations in the queue setup paths
> require large physically contiguous blocks via kmalloc. Under memory
> fragmentation these high-order allocations may fail, preventing the
> driver from creating queues at probe time or when reconfiguring
> channels, ring parameters or MTU at runtime.

## Form letter - net-next-closed

We have already submitted our pull request with net-next material for v7.1,
and therefore net-next is closed for new drivers, features, code refactoring
and optimizations. We are currently accepting bug fixes only.

Please repost when net-next reopens after Apr 27th.

RFC patches sent for review only are obviously welcome at any time.

See: https://www.kernel.org/doc/html/next/process/maintainer-netdev.html#development-cycle
-- 
pw-bot: defer
pv-bot: closed