[SRU][J:linux-azure][PATCH 2/2] net: mana: Use page pool fragments for RX buffers instead of full pages to improve memory efficiency.
John Cabaj
john.cabaj at canonical.com
Fri Dec 5 15:54:10 UTC 2025
From: Dipayaan Roy <dipayanroy at linux.microsoft.com>
BugLink: https://bugs.launchpad.net/bugs/2133750
This patch enhances RX buffer handling in the mana driver by allocating
pages from a page pool and slicing them into MTU-sized fragments, rather
than dedicating a full page per packet. This approach is especially
beneficial on systems with large base page sizes like 64KB.
Key improvements:
- Proper integration of page pool for RX buffer allocations.
- MTU-sized buffer slicing to improve memory utilization.
- Reduce overall per Rx queue memory footprint.
- Automatic fallback to full-page buffers when:
* Jumbo frames are enabled (MTU > PAGE_SIZE / 2).
* The XDP path is active, to avoid complexities with fragment reuse.
Testing on VMs with 64KB pages shows around 200% throughput improvement.
Memory efficiency is significantly improved due to reduced wastage in page
allocations. Example: We are now able to fit 35 rx buffers in a single 64kb
page for MTU size of 1500, instead of 1 rx buffer per page previously.
Tested:
- iperf3, iperf2, and nttcp benchmarks.
- Jumbo frames with MTU 9000.
- Native XDP programs (XDP_PASS, XDP_DROP, XDP_TX, XDP_REDIRECT) for
testing the XDP path in driver.
- Memory leak detection (kmemleak).
- Driver load/unload, reboot, and stress scenarios.
Reviewed-by: Jacob Keller <jacob.e.keller at intel.com>
Reviewed-by: Saurabh Sengar <ssengar at linux.microsoft.com>
Reviewed-by: Haiyang Zhang <haiyangz at microsoft.com>
Signed-off-by: Dipayaan Roy <dipayanroy at linux.microsoft.com>
Link: https://patch.msgid.link/20250814140410.GA22089@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net
Signed-off-by: Paolo Abeni <pabeni at redhat.com>
(backported from commit 730ff06d3f5cc2ce0348414b78c10528b767d4a3 linux-next)
[john-cabaj: leaving out page pool queue_idx specifier, as it doesn't appear
explicitly requried unless PP_FLAG_ALLOW_UNREADABLE_NETMEM flag is set, while
the MANA driver has flags set to PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV. It was
also determined that the PP_FLAG_PAGE_FRAG needs to be added to the flags set,
so that change has been manually made here. Also removing mana_en_need_log()
function added context from upstream fbe346ce9d62: "net: mana: Handle Reset
Request from MANA NIC" as it's not relevant. Finally, page_pool_free_va()
was introduced in the 6.7 kernel, so rather replacing with the contents of
the inline call]
Signed-off-by: John Cabaj <john.cabaj at canonical.com>
---
.../net/ethernet/microsoft/mana/mana_bpf.c | 46 +++++-
drivers/net/ethernet/microsoft/mana/mana_en.c | 150 ++++++++++++------
include/net/mana/mana.h | 4 +
3 files changed, 149 insertions(+), 51 deletions(-)
diff --git a/drivers/net/ethernet/microsoft/mana/mana_bpf.c b/drivers/net/ethernet/microsoft/mana/mana_bpf.c
index 23b1521c0df96..426852939338c 100644
--- a/drivers/net/ethernet/microsoft/mana/mana_bpf.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_bpf.c
@@ -174,6 +174,7 @@ static int mana_xdp_set(struct net_device *ndev, struct bpf_prog *prog,
struct mana_port_context *apc = netdev_priv(ndev);
struct bpf_prog *old_prog;
struct gdma_context *gc;
+ int err;
gc = apc->ac->gdma_dev->gdma_context;
@@ -195,11 +196,45 @@ static int mana_xdp_set(struct net_device *ndev, struct bpf_prog *prog,
*/
apc->bpf_prog = prog;
- if (old_prog)
- bpf_prog_put(old_prog);
+ if (apc->port_is_up) {
+ /* Re-create rxq's after xdp prog was loaded or unloaded.
+ * Ex: re create rxq's to switch from full pages to smaller
+ * size page fragments when xdp prog is unloaded and
+ * vice-versa.
+ */
+
+ /* Pre-allocate buffers to prevent failure in mana_attach */
+ err = mana_pre_alloc_rxbufs(apc, ndev->mtu, apc->num_queues);
+ if (err) {
+ NL_SET_ERR_MSG_MOD(extack,
+ "XDP: Insufficient memory for tx/rx re-config");
+ return err;
+ }
+
+ err = mana_detach(ndev, false);
+ if (err) {
+ netdev_err(ndev,
+ "mana_detach failed at xdp set: %d\n", err);
+ NL_SET_ERR_MSG_MOD(extack,
+ "XDP: Re-config failed at detach");
+ goto err_dealloc_rxbuffs;
+ }
+
+ err = mana_attach(ndev);
+ if (err) {
+ netdev_err(ndev,
+ "mana_attach failed at xdp set: %d\n", err);
+ NL_SET_ERR_MSG_MOD(extack,
+ "XDP: Re-config failed at attach");
+ goto err_dealloc_rxbuffs;
+ }
- if (apc->port_is_up)
mana_chn_setxdp(apc, prog);
+ mana_pre_dealloc_rxbufs(apc);
+ }
+
+ if (old_prog)
+ bpf_prog_put(old_prog);
if (prog)
ndev->max_mtu = MANA_XDP_MTU_MAX;
@@ -207,6 +242,11 @@ static int mana_xdp_set(struct net_device *ndev, struct bpf_prog *prog,
ndev->max_mtu = gc->adapter_mtu - ETH_HLEN;
return 0;
+
+err_dealloc_rxbuffs:
+ apc->bpf_prog = old_prog;
+ mana_pre_dealloc_rxbufs(apc);
+ return err;
}
int mana_bpf(struct net_device *ndev, struct netdev_bpf *bpf)
diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
index 945c5871025fe..7e6d69d51a35c 100644
--- a/drivers/net/ethernet/microsoft/mana/mana_en.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
@@ -44,6 +44,15 @@ static const struct file_operations mana_dbg_q_fops = {
.read = mana_dbg_q_read,
};
+static void mana_put_rx_page(struct mana_rxq *rxq, struct page *page,
+ bool from_pool)
+{
+ if (from_pool)
+ page_pool_put_full_page(rxq->page_pool, page, false);
+ else
+ put_page(page);
+}
+
/* Microsoft Azure Network Adapter (MANA) functions */
static int mana_open(struct net_device *ndev)
@@ -614,21 +623,40 @@ static void *mana_get_rxbuf_pre(struct mana_rxq *rxq, dma_addr_t *da)
}
/* Get RX buffer's data size, alloc size, XDP headroom based on MTU */
-static void mana_get_rxbuf_cfg(int mtu, u32 *datasize, u32 *alloc_size,
- u32 *headroom)
+static void mana_get_rxbuf_cfg(struct mana_port_context *apc,
+ int mtu, u32 *datasize, u32 *alloc_size,
+ u32 *headroom, u32 *frag_count)
{
- if (mtu > MANA_XDP_MTU_MAX)
- *headroom = 0; /* no support for XDP */
- else
- *headroom = XDP_PACKET_HEADROOM;
+ u32 len, buf_size;
- *alloc_size = SKB_DATA_ALIGN(mtu + MANA_RXBUF_PAD + *headroom);
+ /* Calculate datasize first (consistent across all cases) */
+ *datasize = mtu + ETH_HLEN;
- /* Using page pool in this case, so alloc_size is PAGE_SIZE */
- if (*alloc_size < PAGE_SIZE)
- *alloc_size = PAGE_SIZE;
+ /* For xdp and jumbo frames make sure only one packet fits per page */
+ if (mtu + MANA_RXBUF_PAD > PAGE_SIZE / 2 || mana_xdp_get(apc)) {
+ if (mana_xdp_get(apc)) {
+ *headroom = XDP_PACKET_HEADROOM;
+ *alloc_size = PAGE_SIZE;
+ } else {
+ *headroom = 0; /* no support for XDP */
+ *alloc_size = SKB_DATA_ALIGN(mtu + MANA_RXBUF_PAD +
+ *headroom);
+ }
- *datasize = mtu + ETH_HLEN;
+ *frag_count = 1;
+ return;
+ }
+
+ /* Standard MTU case - optimize for multiple packets per page */
+ *headroom = 0;
+
+ /* Calculate base buffer size needed */
+ len = SKB_DATA_ALIGN(mtu + MANA_RXBUF_PAD + *headroom);
+ buf_size = ALIGN(len, MANA_RX_FRAG_ALIGNMENT);
+
+ /* Calculate how many packets can fit in a page */
+ *frag_count = PAGE_SIZE / buf_size;
+ *alloc_size = buf_size;
}
int mana_pre_alloc_rxbufs(struct mana_port_context *mpc, int new_mtu, int num_queues)
@@ -640,8 +668,9 @@ int mana_pre_alloc_rxbufs(struct mana_port_context *mpc, int new_mtu, int num_qu
void *va;
int i;
- mana_get_rxbuf_cfg(new_mtu, &mpc->rxbpre_datasize,
- &mpc->rxbpre_alloc_size, &mpc->rxbpre_headroom);
+ mana_get_rxbuf_cfg(mpc, new_mtu, &mpc->rxbpre_datasize,
+ &mpc->rxbpre_alloc_size, &mpc->rxbpre_headroom,
+ &mpc->rxbpre_frag_count);
dev = mpc->ac->gdma_dev->gdma_context->dev;
@@ -1645,8 +1674,11 @@ static void mana_rx_skb(void *buf_va, bool from_pool,
drop:
if (from_pool) {
- page_pool_recycle_direct(rxq->page_pool,
- virt_to_head_page(buf_va));
+ if (rxq->frag_count == 1)
+ page_pool_recycle_direct(rxq->page_pool,
+ virt_to_head_page(buf_va));
+ else
+ page_pool_put_page(rxq->page_pool, virt_to_head_page(buf_va), -1, true);
} else {
WARN_ON_ONCE(rxq->xdp_save_va);
/* Save for reuse */
@@ -1662,33 +1694,46 @@ static void *mana_get_rxfrag(struct mana_rxq *rxq, struct device *dev,
dma_addr_t *da, bool *from_pool)
{
struct page *page;
+ u32 offset;
void *va;
-
*from_pool = false;
- /* Reuse XDP dropped page if available */
- if (rxq->xdp_save_va) {
- va = rxq->xdp_save_va;
- rxq->xdp_save_va = NULL;
- } else {
- page = page_pool_dev_alloc_pages(rxq->page_pool);
- if (!page)
+ /* Don't use fragments for jumbo frames or XDP where it's 1 fragment
+ * per page.
+ */
+ if (rxq->frag_count == 1) {
+ /* Reuse XDP dropped page if available */
+ if (rxq->xdp_save_va) {
+ va = rxq->xdp_save_va;
+ page = virt_to_head_page(va);
+ rxq->xdp_save_va = NULL;
+ } else {
+ page = page_pool_dev_alloc_pages(rxq->page_pool);
+ if (!page)
+ return NULL;
+
+ *from_pool = true;
+ va = page_to_virt(page);
+ }
+
+ *da = dma_map_single(dev, va + rxq->headroom, rxq->datasize,
+ DMA_FROM_DEVICE);
+ if (dma_mapping_error(dev, *da)) {
+ mana_put_rx_page(rxq, page, *from_pool);
return NULL;
+ }
- *from_pool = true;
- va = page_to_virt(page);
+ return va;
}
- *da = dma_map_single(dev, va + rxq->headroom, rxq->datasize,
- DMA_FROM_DEVICE);
- if (dma_mapping_error(dev, *da)) {
- if (*from_pool)
- page_pool_put_full_page(rxq->page_pool, page, false);
- else
- put_page(virt_to_head_page(va));
-
+ page = page_pool_dev_alloc_frag(rxq->page_pool, &offset,
+ rxq->alloc_size);
+ if (!page)
return NULL;
- }
+
+ va = page_to_virt(page) + offset;
+ *da = page_pool_get_dma_addr(page) + offset + rxq->headroom;
+ *from_pool = true;
return va;
}
@@ -1705,9 +1750,9 @@ static void mana_refill_rx_oob(struct device *dev, struct mana_rxq *rxq,
va = mana_get_rxfrag(rxq, dev, &da, &from_pool);
if (!va)
return;
-
- dma_unmap_single(dev, rxoob->sgl[0].address, rxq->datasize,
- DMA_FROM_DEVICE);
+ if (!rxoob->from_pool || rxq->frag_count == 1)
+ dma_unmap_single(dev, rxoob->sgl[0].address, rxq->datasize,
+ DMA_FROM_DEVICE);
*old_buf = rxoob->buf_va;
*old_fp = rxoob->from_pool;
@@ -2113,15 +2158,15 @@ static void mana_destroy_rxq(struct mana_port_context *apc,
if (!rx_oob->buf_va)
continue;
- dma_unmap_single(dev, rx_oob->sgl[0].address,
- rx_oob->sgl[0].size, DMA_FROM_DEVICE);
-
page = virt_to_head_page(rx_oob->buf_va);
- if (rx_oob->from_pool)
- page_pool_put_full_page(rxq->page_pool, page, false);
- else
- put_page(page);
+ if (rxq->frag_count == 1 || !rx_oob->from_pool) {
+ dma_unmap_single(dev, rx_oob->sgl[0].address,
+ rx_oob->sgl[0].size, DMA_FROM_DEVICE);
+ mana_put_rx_page(rxq, page, rx_oob->from_pool);
+ } else {
+ page_pool_put_page(rxq->page_pool, virt_to_head_page(rx_oob->buf_va), -1, true);
+ }
rx_oob->buf_va = NULL;
}
@@ -2227,9 +2272,19 @@ static int mana_create_page_pool(struct mana_rxq *rxq, struct gdma_context *gc)
struct page_pool_params pprm = {};
int ret;
- pprm.pool_size = mpc->rx_queue_size;
+ pprm.pool_size = mpc->rx_queue_size / rxq->frag_count + 1;
pprm.nid = gc->numa_node;
pprm.order = get_order(rxq->alloc_size);
+ pprm.dev = gc->dev;
+
+ /* Let the page pool do the dma map when page sharing with multiple
+ * fragments enabled for rx buffers.
+ */
+ if (rxq->frag_count > 1) {
+ pprm.flags = PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV | PP_FLAG_PAGE_FRAG;
+ pprm.max_len = PAGE_SIZE;
+ pprm.dma_dir = DMA_FROM_DEVICE;
+ }
rxq->page_pool = page_pool_create(&pprm);
@@ -2268,9 +2323,8 @@ static struct mana_rxq *mana_create_rxq(struct mana_port_context *apc,
rxq->rxq_idx = rxq_idx;
rxq->rxobj = INVALID_MANA_HANDLE;
- mana_get_rxbuf_cfg(ndev->mtu, &rxq->datasize, &rxq->alloc_size,
- &rxq->headroom);
-
+ mana_get_rxbuf_cfg(apc, ndev->mtu, &rxq->datasize, &rxq->alloc_size,
+ &rxq->headroom, &rxq->frag_count);
/* Create page pool for RX queue */
err = mana_create_page_pool(rxq, gc);
if (err) {
diff --git a/include/net/mana/mana.h b/include/net/mana/mana.h
index e81e259cf5cf6..8cfd103de0226 100644
--- a/include/net/mana/mana.h
+++ b/include/net/mana/mana.h
@@ -62,6 +62,8 @@ enum TRI_STATE {
#define MANA_STATS_RX_COUNT 5
#define MANA_STATS_TX_COUNT 11
+#define MANA_RX_FRAG_ALIGNMENT 64
+
struct mana_stats_rx {
u64 packets;
u64 bytes;
@@ -325,6 +327,7 @@ struct mana_rxq {
u32 datasize;
u32 alloc_size;
u32 headroom;
+ u32 frag_count;
mana_handle_t rxobj;
@@ -487,6 +490,7 @@ struct mana_port_context {
u32 rxbpre_datasize;
u32 rxbpre_alloc_size;
u32 rxbpre_headroom;
+ u32 rxbpre_frag_count;
struct bpf_prog *bpf_prog;
--
2.43.0
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