net: mana: add ethtool private flag for full-page RX buffers
Subsystems (6)
v9 cover net: mana: add ethtool private flag for full-page RX buffers
On some ARM64 platforms with 4K PAGE_SIZE, utilizing page_pool fragments for allocation in the RX refill path (~2kB buffer per fragment) causes 15-20% throughput regression under high connection counts (>16 TCP streams at 180+ Gbps). Using full-page buffers on these platforms shows no regression and restores line-rate performance.
This behavior is observed on a single platform; other platforms perform better with page_pool fragments, indicating this is not a page_pool issue but platform-specific.
This series adds an ethtool private flag "full-page-rx" to let the user opt in to one RX buffer per page:
ethtool --set-priv-flags eth0 full-page-rx on
There is no behavioral change by default. The flag can be persisted via udev rule for affected platforms.
Changes in v9:
- Added coorect tree.
Changes in v8:
- Fixed queue_reset_work recovery by restoring port_is_up before scheduling reset so the handler can properly re-attach.
- Simplified "err && schedule_port_reset" to "schedule_port_reset".
Changes in v7:
- Rebased onto net-next.
- Retained private flag approach after David Wei's testing on Grace (ARM64) confirmed that fragment mode outperforms full-page mode on other platforms, validating this is a single-platform workaround rather than a generic issue.
Changes in v6:
- Added missed maintainers.
Changes in v5:
- Split prep refactor into separate patch (patch 1/2)
Changes in v4:
- Dropping the smbios string parsing and add ethtool priv flag to reconfigure the queues with full page rx buffers.
Changes in v3:
- changed u8* to char*
Changes in v2:
- separate reading string index and the string, remove inline.
Dipayaan Roy (2):
net: mana: refactor mana_get_strings() and mana_get_sset_count() to
use switch
net: mana: force full-page RX buffers via ethtool private flag
drivers/net/ethernet/microsoft/mana/mana_en.c | 22 ++- .../ethernet/microsoft/mana/mana_ethtool.c | 178 +++++++++++++++--- include/net/mana/mana.h | 8 + 3 files changed, 177 insertions(+), 31 deletions(-)
Signature · 1 line
2.43.0
PATCH v9 1/2 net: mana: refactor mana_get_strings() and mana_get_sset_count() to use switch
Refactor mana_get_strings() and mana_get_sset_count() from if/else to switch statements in preparation for adding ethtool private flags support which requires handling ETH_SS_PRIV_FLAGS.
No functional change.
--- .../ethernet/microsoft/mana/mana_ethtool.c | 75 ++++++++++++------- 1 file changed, 46 insertions(+), 29 deletions(-)
drivers/net/ethernet/microsoft/mana/mana_ethtool.c +46 -29
@@ -138,53 +138,70 @@ static int mana_get_sset_count(struct net_device *ndev, int stringset)struct mana_port_context *apc =netdev_priv (ndev);unsigned int num_queues = apc->num_queues; -if (stringset !=ETH_SS_STATS ) +switch (stringset) { +case ETH_SS_STATS : +return ARRAY_SIZE (mana_eth_stats) + +ARRAY_SIZE (mana_phy_stats) + +ARRAY_SIZE (mana_hc_stats) + + num_queues * (MANA_STATS_RX_COUNT +MANA_STATS_TX_COUNT ); +default :return -EINVAL ; - -return ARRAY_SIZE (mana_eth_stats) +ARRAY_SIZE (mana_phy_stats) +ARRAY_SIZE (mana_hc_stats) + - num_queues * (MANA_STATS_RX_COUNT +MANA_STATS_TX_COUNT ); + } } -static void mana_get_strings (struct net_device *ndev,u32 stringset,u8 *data) +static void mana_get_strings_stats (struct mana_port_context *apc,u8 **data) { -struct mana_port_context *apc =netdev_priv (ndev);unsigned int num_queues = apc->num_queues;int i, j; -if (stringset !=ETH_SS_STATS ) -return ;for (i =0 ; i <ARRAY_SIZE (mana_eth_stats); i++) -ethtool_puts (&data, mana_eth_stats[i].name); +ethtool_puts (data, mana_eth_stats[i].name);for (i =0 ; i <ARRAY_SIZE (mana_hc_stats); i++) -ethtool_puts (&data, mana_hc_stats[i].name); +ethtool_puts (data, mana_hc_stats[i].name);for (i =0 ; i <ARRAY_SIZE (mana_phy_stats); i++) -ethtool_puts (&data, mana_phy_stats[i].name); +ethtool_puts (data, mana_phy_stats[i].name);for (i =0 ; i < num_queues; i++) { -ethtool_sprintf (&data,"rx_%d_packets" , i); -ethtool_sprintf (&data,"rx_%d_bytes" , i); -ethtool_sprintf (&data,"rx_%d_xdp_drop" , i); -ethtool_sprintf (&data,"rx_%d_xdp_tx" , i); -ethtool_sprintf (&data,"rx_%d_xdp_redirect" , i); -ethtool_sprintf (&data,"rx_%d_pkt_len0_err" , i); +ethtool_sprintf (data,"rx_%d_packets" , i); +ethtool_sprintf (data,"rx_%d_bytes" , i); +ethtool_sprintf (data,"rx_%d_xdp_drop" , i); +ethtool_sprintf (data,"rx_%d_xdp_tx" , i); +ethtool_sprintf (data,"rx_%d_xdp_redirect" , i); +ethtool_sprintf (data,"rx_%d_pkt_len0_err" , i);for (j =0 ; j <MANA_RXCOMP_OOB_NUM_PPI -1 ; j++) -ethtool_sprintf (&data,"rx_%d_coalesced_cqe_%d" , i, j +2 ); +ethtool_sprintf (data, +"rx_%d_coalesced_cqe_%d" , + i, + j +2 ); }for (i =0 ; i < num_queues; i++) { -ethtool_sprintf (&data,"tx_%d_packets" , i); -ethtool_sprintf (&data,"tx_%d_bytes" , i); -ethtool_sprintf (&data,"tx_%d_xdp_xmit" , i); -ethtool_sprintf (&data,"tx_%d_tso_packets" , i); -ethtool_sprintf (&data,"tx_%d_tso_bytes" , i); -ethtool_sprintf (&data,"tx_%d_tso_inner_packets" , i); -ethtool_sprintf (&data,"tx_%d_tso_inner_bytes" , i); -ethtool_sprintf (&data,"tx_%d_long_pkt_fmt" , i); -ethtool_sprintf (&data,"tx_%d_short_pkt_fmt" , i); -ethtool_sprintf (&data,"tx_%d_csum_partial" , i); -ethtool_sprintf (&data,"tx_%d_mana_map_err" , i); +ethtool_sprintf (data,"tx_%d_packets" , i); +ethtool_sprintf (data,"tx_%d_bytes" , i); +ethtool_sprintf (data,"tx_%d_xdp_xmit" , i); +ethtool_sprintf (data,"tx_%d_tso_packets" , i); +ethtool_sprintf (data,"tx_%d_tso_bytes" , i); +ethtool_sprintf (data,"tx_%d_tso_inner_packets" , i); +ethtool_sprintf (data,"tx_%d_tso_inner_bytes" , i); +ethtool_sprintf (data,"tx_%d_long_pkt_fmt" , i); +ethtool_sprintf (data,"tx_%d_short_pkt_fmt" , i); +ethtool_sprintf (data,"tx_%d_csum_partial" , i); +ethtool_sprintf (data,"tx_%d_mana_map_err" , i); + } +} + +static void mana_get_strings (struct net_device *ndev,u32 stringset,u8 *data) +{ +struct mana_port_context *apc =netdev_priv (ndev); + +switch (stringset) { +case ETH_SS_STATS : +mana_get_strings_stats (apc, &data); +break ; +default : +break ; } }
Signature · 1 line
2.43.0
PATCH v9 2/2 net: mana: force full-page RX buffers via ethtool private flag
In reply to Dipayaan RoyOn some ARM64 platforms with 4K PAGE_SIZE, page_pool fragment allocation in the RX refill path can cause 15-20% throughput regression under high connection counts (>16 TCP streams).
Add an ethtool private flag "full-page-rx" that allows the user to force one RX buffer per page, bypassing the page_pool fragment path. This restores line-rate (180+ Gbps) performance on affected platforms.
Usage:
ethtool --set-priv-flags eth0 full-page-rx on
There is no behavioral change by default. The flag must be explicitly enabled by the user or udev rule.
The existing single-buffer-per-page logic for XDP and jumbo frames is consolidated into a new helper mana_use_single_rxbuf_per_page() which is now the single decision point for both the automatic and user-controlled paths.
--- drivers/net/ethernet/microsoft/mana/mana_en.c | 22 +++- .../ethernet/microsoft/mana/mana_ethtool.c | 103 ++++++++++++++++++ include/net/mana/mana.h | 8 ++ 3 files changed, 131 insertions(+), 2 deletions(-)
drivers/net/ethernet/microsoft/mana/mana_en.c +20 -2
@@ -744,6 +744,25 @@ static void *mana_get_rxbuf_pre(struct mana_rxq *rxq, dma_addr_t *da)return va; } +static bool +mana_use_single_rxbuf_per_page (struct mana_port_context *apc,u32 mtu) +{ +/* On some platforms with 4K PAGE_SIZE, page_pool fragment allocation +* in the RX refill path (~2kB buffer) can cause significant throughput +* regression under high connection counts. Allow user to force one RX +* buffer per page via ethtool private flag to bypass the fragment +* path. +*/ +if (apc->priv_flags &BIT (MANA_PRIV_FLAG_USE_FULL_PAGE_RXBUF )) +return true; + +/* 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)) +return true; + +return false; +} +/* Get RX buffer's data size, alloc size, XDP headroom based on MTU */ static void mana_get_rxbuf_cfg(struct mana_port_context *apc, int mtu, u32 *datasize, u32 *alloc_size,
@@ -754,8 +773,7 @@ static void mana_get_rxbuf_cfg(struct mana_port_context *apc,/* Calculate datasize first (consistent across all cases) */ *datasize = mtu +ETH_HLEN ; -/* 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_use_single_rxbuf_per_page (apc, mtu)) {if (mana_xdp_get (apc)) { *headroom =XDP_PACKET_HEADROOM ; *alloc_size =PAGE_SIZE ;
drivers/net/ethernet/microsoft/mana/mana_ethtool.c +103 -0
137 lines not on this page · raw message
include/net/mana/mana.h +8 -0
@@ -30,6 +30,12 @@ enum TRI_STATE { TRI_STATE_TRUE = 1 }; +/* MANA ethtool private flag bit positions */ +enum mana_priv_flag_bits { +MANA_PRIV_FLAG_USE_FULL_PAGE_RXBUF =0 , +MANA_PRIV_FLAG_MAX , +}; +/* Number of entries for hardware indirection table must be in power of 2 */ #define MANA_INDIRECT_TABLE_MAX_SIZE 512#define MANA_INDIRECT_TABLE_DEF_SIZE 64
@@ -531,6 +537,8 @@ struct mana_port_context {u32 rxbpre_headroom;u32 rxbpre_frag_count; +u32 priv_flags; +struct bpf_prog *bpf_prog;/* Create num_queues EQs, SQs, SQ-CQs, RQs and RQ-CQs, respectively. */
Signature · 1 line
2.43.0
[email protected]
AI reviewRe: [PATCH net-next,v9 2/2] net: mana: force full-page RX buffers via ethtool private flag
Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: - [High] Forcing `apc->port_is_up = true` in the `mana_attach` error path causes a guaranteed NULL pointer…
Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Forcing apc->port_is_up = true in the mana_attach error path causes a guaranteed NULL pointer dereference in the reset worker. --
commit d36beb9b51f56b9797284c9fa1dd515410680980
Author: Dipayaan Roy <[email protected]>
Subject: net: mana: force full-page RX buffers via ethtool private flag
This patch adds an ethtool private flag full-page-rx that allows the user to force one RX buffer per page, bypassing the page_pool fragment path on ARM64 platforms with 4K PAGE_SIZE.
Quoted 4 lines
drivers/net/ethernet/microsoft/mana/mana_ethtool.c +0
-0
[ ... ]
Quoted 1 line
drivers/net/ethernet/microsoft/mana/mana_ethtool.c +0
-0@@ -590,6 +609,88 @@ static int mana_get_link_ksettings(struct net_device *ndev,
[ ... ]
Quoted 2 lines
drivers/net/ethernet/microsoft/mana/mana_ethtool.c +2
-0+static int mana_set_priv_flags (struct net_device *ndev,u32 priv_flags) +{
[ ... ]
drivers/net/ethernet/microsoft/mana/mana_ethtool.c static int mana_get_link_ksettings(struct net_device *ndev, · line 681
Quoted 13 lines
drivers/net/ethernet/microsoft/mana/mana_ethtool.c +13
-0+ err =mana_attach (ndev); +if (err) { +netdev_err (ndev,"mana_attach failed: %d\n" , err); + apc->priv_flags = old_priv_flags; + +/* Restore 'port_is_up' so the reset work handler +* can properly detach/attach. Without this, +* the handler sees port_is_up=false and skips +* queue allocation, leaving the port dead. +*/ + apc->port_is_up = true; + schedule_port_reset = true; + }
Can this cause a NULL pointer dereference in the reset worker?
If mana_attach() fails, its error path cleans up the partially allocated state. Specifically, if mana_alloc_queues() fails, it calls mana_cleanup_port_context(), which frees the tx_qp array and sets apc->tx_qp = NULL.
When apc->port_is_up is forced to true and the reset work is scheduled here:
mana_set_priv_flags()
err = mana_attach(ndev);
if (err) {
...
apc->port_is_up = true;
schedule_port_reset = true;}
The reset worker will eventually call mana_detach(). Because apc->port_is_up is true, mana_detach() will attempt to deallocate the queues:
mana_detach()
apc->port_st_save = apc->port_is_up;
...
if (apc->port_st_save) {
err = mana_dealloc_queues(ndev);If mana_dealloc_queues() unconditionally iterates over apc->num_queues and accesses apc->tx_qp[i], does this lead to an immediate kernel panic since apc->tx_qp was already set to NULL during the earlier cleanup?
Signature · 1 line
Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=2