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Message-ID: <20250904211254.1057445-2-pasic@linux.ibm.com>
Date: Thu, 4 Sep 2025 23:12:52 +0200
From: Halil Pasic <pasic@...ux.ibm.com>
To: Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Simon Horman <horms@...nel.org>,
"D. Wythe" <alibuda@...ux.alibaba.com>,
Dust Li <dust.li@...ux.alibaba.com>,
Sidraya Jayagond <sidraya@...ux.ibm.com>,
Wenjia Zhang <wenjia@...ux.ibm.com>,
Mahanta Jambigi <mjambigi@...ux.ibm.com>,
Tony Lu <tonylu@...ux.alibaba.com>, Wen Gu <guwen@...ux.alibaba.com>,
netdev@...r.kernel.org, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-rdma@...r.kernel.org,
linux-s390@...r.kernel.org
Cc: Halil Pasic <pasic@...ux.ibm.com>
Subject: [PATCH net-next 1/2] net/smc: make wr buffer count configurable
Think SMC_WR_BUF_CNT_SEND := SMC_WR_BUF_CNT used in send context and
SMC_WR_BUF_CNT_RECV := 3 * SMC_WR_BUF_CNT used in recv context. Those
get replaced with lgr->max_send_wr and lgr->max_recv_wr respective.
While at it let us also remove a confusing comment that is either not
about the context in which it resides (describing
qp_attr.cap.max_send_wr and qp_attr.cap.max_recv_wr) or not applicable
any more when these values become configurable .
Signed-off-by: Halil Pasic <pasic@...ux.ibm.com>
Reviewed-by: Wenjia Zhang <wenjia@...ux.ibm.com>
---
Documentation/networking/smc-sysctl.rst | 37 +++++++++++++++++++++++++
net/smc/smc.h | 2 ++
net/smc/smc_core.h | 4 +++
net/smc/smc_ib.c | 7 ++---
net/smc/smc_llc.c | 2 ++
net/smc/smc_sysctl.c | 22 +++++++++++++++
net/smc/smc_wr.c | 32 +++++++++++----------
net/smc/smc_wr.h | 2 --
8 files changed, 86 insertions(+), 22 deletions(-)
diff --git a/Documentation/networking/smc-sysctl.rst b/Documentation/networking/smc-sysctl.rst
index a874d007f2db..c687092329e3 100644
--- a/Documentation/networking/smc-sysctl.rst
+++ b/Documentation/networking/smc-sysctl.rst
@@ -71,3 +71,40 @@ smcr_max_conns_per_lgr - INTEGER
acceptable value ranges from 16 to 255. Only for SMC-R v2.1 and later.
Default: 255
+
+smcr_max_send_wr - INTEGER
+ So called work request buffers are SMCR link (and RDMA queue pair) level
+ resources necessary for performing RDMA operations. Since up to 255
+ connections can share a link group and thus also a link and the number
+ of the work request buffers is decided when the link is allocated,
+ depending on the workload it can a bottleneck in a sense that threads
+ have to wait for work request buffers to become available. Before the
+ introduction of this control the maximal number of work request buffers
+ available on the send path used to be hard coded to 16. With this control
+ it becomes configurable. The acceptable range is between 2 and 2048.
+
+ Please be aware that all the buffers need to be allocated as a physically
+ continuous array in which each element is a single buffer and has the size
+ of SMC_WR_BUF_SIZE (48) bytes. If the allocation fails we give up much
+ like before having this control.
+ this control.
+
+ Default: 16
+
+smcr_max_recv_wr - INTEGER
+ So called work request buffers are SMCR link (and RDMA queue pair) level
+ resources necessary for performing RDMA operations. Since up to 255
+ connections can share a link group and thus also a link and the number
+ of the work request buffers is decided when the link is allocated,
+ depending on the workload it can a bottleneck in a sense that threads
+ have to wait for work request buffers to become available. Before the
+ introduction of this control the maximal number of work request buffers
+ available on the receive path used to be hard coded to 16. With this control
+ it becomes configurable. The acceptable range is between 2 and 2048.
+
+ Please be aware that all the buffers need to be allocated as a physically
+ continuous array in which each element is a single buffer and has the size
+ of SMC_WR_BUF_SIZE (48) bytes. If the allocation fails we give up much
+ like before having this control.
+
+ Default: 48
diff --git a/net/smc/smc.h b/net/smc/smc.h
index 2c9084963739..ffe48253fa1f 100644
--- a/net/smc/smc.h
+++ b/net/smc/smc.h
@@ -33,6 +33,8 @@
extern struct proto smc_proto;
extern struct proto smc_proto6;
+extern unsigned int smc_ib_sysctl_max_send_wr;
+extern unsigned int smc_ib_sysctl_max_recv_wr;
extern struct smc_hashinfo smc_v4_hashinfo;
extern struct smc_hashinfo smc_v6_hashinfo;
diff --git a/net/smc/smc_core.h b/net/smc/smc_core.h
index 48a1b1dcb576..b883f43fc206 100644
--- a/net/smc/smc_core.h
+++ b/net/smc/smc_core.h
@@ -361,6 +361,10 @@ struct smc_link_group {
/* max conn can be assigned to lgr */
u8 max_links;
/* max links can be added in lgr */
+ u16 max_send_wr;
+ /* number of WR buffers on send */
+ u16 max_recv_wr;
+ /* number of WR buffers on recv */
};
struct { /* SMC-D */
struct smcd_gid peer_gid;
diff --git a/net/smc/smc_ib.c b/net/smc/smc_ib.c
index 0052f02756eb..e8d35c22c525 100644
--- a/net/smc/smc_ib.c
+++ b/net/smc/smc_ib.c
@@ -669,11 +669,6 @@ int smc_ib_create_queue_pair(struct smc_link *lnk)
.recv_cq = lnk->smcibdev->roce_cq_recv,
.srq = NULL,
.cap = {
- /* include unsolicited rdma_writes as well,
- * there are max. 2 RDMA_WRITE per 1 WR_SEND
- */
- .max_send_wr = SMC_WR_BUF_CNT * 3,
- .max_recv_wr = SMC_WR_BUF_CNT * 3,
.max_send_sge = SMC_IB_MAX_SEND_SGE,
.max_recv_sge = lnk->wr_rx_sge_cnt,
.max_inline_data = 0,
@@ -683,6 +678,8 @@ int smc_ib_create_queue_pair(struct smc_link *lnk)
};
int rc;
+ qp_attr.cap.max_send_wr = 3 * lnk->lgr->max_send_wr;
+ qp_attr.cap.max_recv_wr = lnk->lgr->max_recv_wr;
lnk->roce_qp = ib_create_qp(lnk->roce_pd, &qp_attr);
rc = PTR_ERR_OR_ZERO(lnk->roce_qp);
if (IS_ERR(lnk->roce_qp))
diff --git a/net/smc/smc_llc.c b/net/smc/smc_llc.c
index f865c58c3aa7..91c936bf7336 100644
--- a/net/smc/smc_llc.c
+++ b/net/smc/smc_llc.c
@@ -2157,6 +2157,8 @@ void smc_llc_lgr_init(struct smc_link_group *lgr, struct smc_sock *smc)
init_waitqueue_head(&lgr->llc_msg_waiter);
init_rwsem(&lgr->llc_conf_mutex);
lgr->llc_testlink_time = READ_ONCE(net->smc.sysctl_smcr_testlink_time);
+ lgr->max_send_wr = (u16)(READ_ONCE(smc_ib_sysctl_max_send_wr));
+ lgr->max_recv_wr = (u16)(READ_ONCE(smc_ib_sysctl_max_recv_wr));
}
/* called after lgr was removed from lgr_list */
diff --git a/net/smc/smc_sysctl.c b/net/smc/smc_sysctl.c
index 2fab6456f765..01da1297e150 100644
--- a/net/smc/smc_sysctl.c
+++ b/net/smc/smc_sysctl.c
@@ -29,6 +29,10 @@ static int links_per_lgr_min = SMC_LINKS_ADD_LNK_MIN;
static int links_per_lgr_max = SMC_LINKS_ADD_LNK_MAX;
static int conns_per_lgr_min = SMC_CONN_PER_LGR_MIN;
static int conns_per_lgr_max = SMC_CONN_PER_LGR_MAX;
+unsigned int smc_ib_sysctl_max_send_wr = 16;
+unsigned int smc_ib_sysctl_max_recv_wr = 48;
+static unsigned int smc_ib_sysctl_max_wr_min = 2;
+static unsigned int smc_ib_sysctl_max_wr_max = 2048;
static struct ctl_table smc_table[] = {
{
@@ -99,6 +103,24 @@ static struct ctl_table smc_table[] = {
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_ONE,
},
+ {
+ .procname = "smcr_max_send_wr",
+ .data = &smc_ib_sysctl_max_send_wr,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = &smc_ib_sysctl_max_wr_min,
+ .extra2 = &smc_ib_sysctl_max_wr_max,
+ },
+ {
+ .procname = "smcr_max_recv_wr",
+ .data = &smc_ib_sysctl_max_recv_wr,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = &smc_ib_sysctl_max_wr_min,
+ .extra2 = &smc_ib_sysctl_max_wr_max,
+ },
};
int __net_init smc_sysctl_net_init(struct net *net)
diff --git a/net/smc/smc_wr.c b/net/smc/smc_wr.c
index b04a21b8c511..85ebc65f1546 100644
--- a/net/smc/smc_wr.c
+++ b/net/smc/smc_wr.c
@@ -34,6 +34,7 @@
#define SMC_WR_MAX_POLL_CQE 10 /* max. # of compl. queue elements in 1 poll */
#define SMC_WR_RX_HASH_BITS 4
+
static DEFINE_HASHTABLE(smc_wr_rx_hash, SMC_WR_RX_HASH_BITS);
static DEFINE_SPINLOCK(smc_wr_rx_hash_lock);
@@ -547,9 +548,9 @@ void smc_wr_remember_qp_attr(struct smc_link *lnk)
IB_QP_DEST_QPN,
&init_attr);
- lnk->wr_tx_cnt = min_t(size_t, SMC_WR_BUF_CNT,
+ lnk->wr_tx_cnt = min_t(size_t, lnk->lgr->max_send_wr,
lnk->qp_attr.cap.max_send_wr);
- lnk->wr_rx_cnt = min_t(size_t, SMC_WR_BUF_CNT * 3,
+ lnk->wr_rx_cnt = min_t(size_t, lnk->lgr->max_recv_wr,
lnk->qp_attr.cap.max_recv_wr);
}
@@ -741,50 +742,51 @@ int smc_wr_alloc_lgr_mem(struct smc_link_group *lgr)
int smc_wr_alloc_link_mem(struct smc_link *link)
{
/* allocate link related memory */
- link->wr_tx_bufs = kcalloc(SMC_WR_BUF_CNT, SMC_WR_BUF_SIZE, GFP_KERNEL);
+ link->wr_tx_bufs = kcalloc(link->lgr->max_send_wr,
+ SMC_WR_BUF_SIZE, GFP_KERNEL);
if (!link->wr_tx_bufs)
goto no_mem;
- link->wr_rx_bufs = kcalloc(SMC_WR_BUF_CNT * 3, link->wr_rx_buflen,
+ link->wr_rx_bufs = kcalloc(link->lgr->max_recv_wr, SMC_WR_BUF_SIZE,
GFP_KERNEL);
if (!link->wr_rx_bufs)
goto no_mem_wr_tx_bufs;
- link->wr_tx_ibs = kcalloc(SMC_WR_BUF_CNT, sizeof(link->wr_tx_ibs[0]),
- GFP_KERNEL);
+ link->wr_tx_ibs = kcalloc(link->lgr->max_send_wr,
+ sizeof(link->wr_tx_ibs[0]), GFP_KERNEL);
if (!link->wr_tx_ibs)
goto no_mem_wr_rx_bufs;
- link->wr_rx_ibs = kcalloc(SMC_WR_BUF_CNT * 3,
+ link->wr_rx_ibs = kcalloc(link->lgr->max_recv_wr,
sizeof(link->wr_rx_ibs[0]),
GFP_KERNEL);
if (!link->wr_rx_ibs)
goto no_mem_wr_tx_ibs;
- link->wr_tx_rdmas = kcalloc(SMC_WR_BUF_CNT,
+ link->wr_tx_rdmas = kcalloc(link->lgr->max_send_wr,
sizeof(link->wr_tx_rdmas[0]),
GFP_KERNEL);
if (!link->wr_tx_rdmas)
goto no_mem_wr_rx_ibs;
- link->wr_tx_rdma_sges = kcalloc(SMC_WR_BUF_CNT,
+ link->wr_tx_rdma_sges = kcalloc(link->lgr->max_send_wr,
sizeof(link->wr_tx_rdma_sges[0]),
GFP_KERNEL);
if (!link->wr_tx_rdma_sges)
goto no_mem_wr_tx_rdmas;
- link->wr_tx_sges = kcalloc(SMC_WR_BUF_CNT, sizeof(link->wr_tx_sges[0]),
+ link->wr_tx_sges = kcalloc(link->lgr->max_send_wr, sizeof(link->wr_tx_sges[0]),
GFP_KERNEL);
if (!link->wr_tx_sges)
goto no_mem_wr_tx_rdma_sges;
- link->wr_rx_sges = kcalloc(SMC_WR_BUF_CNT * 3,
+ link->wr_rx_sges = kcalloc(link->lgr->max_recv_wr,
sizeof(link->wr_rx_sges[0]) * link->wr_rx_sge_cnt,
GFP_KERNEL);
if (!link->wr_rx_sges)
goto no_mem_wr_tx_sges;
- link->wr_tx_mask = bitmap_zalloc(SMC_WR_BUF_CNT, GFP_KERNEL);
+ link->wr_tx_mask = bitmap_zalloc(link->lgr->max_send_wr, GFP_KERNEL);
if (!link->wr_tx_mask)
goto no_mem_wr_rx_sges;
- link->wr_tx_pends = kcalloc(SMC_WR_BUF_CNT,
+ link->wr_tx_pends = kcalloc(link->lgr->max_send_wr,
sizeof(link->wr_tx_pends[0]),
GFP_KERNEL);
if (!link->wr_tx_pends)
goto no_mem_wr_tx_mask;
- link->wr_tx_compl = kcalloc(SMC_WR_BUF_CNT,
+ link->wr_tx_compl = kcalloc(link->lgr->max_send_wr,
sizeof(link->wr_tx_compl[0]),
GFP_KERNEL);
if (!link->wr_tx_compl)
@@ -905,7 +907,7 @@ int smc_wr_create_link(struct smc_link *lnk)
goto dma_unmap;
}
smc_wr_init_sge(lnk);
- bitmap_zero(lnk->wr_tx_mask, SMC_WR_BUF_CNT);
+ bitmap_zero(lnk->wr_tx_mask, lnk->lgr->max_send_wr);
init_waitqueue_head(&lnk->wr_tx_wait);
rc = percpu_ref_init(&lnk->wr_tx_refs, smcr_wr_tx_refs_free, 0, GFP_KERNEL);
if (rc)
diff --git a/net/smc/smc_wr.h b/net/smc/smc_wr.h
index f3008dda222a..aa4533af9122 100644
--- a/net/smc/smc_wr.h
+++ b/net/smc/smc_wr.h
@@ -19,8 +19,6 @@
#include "smc.h"
#include "smc_core.h"
-#define SMC_WR_BUF_CNT 16 /* # of ctrl buffers per link */
-
#define SMC_WR_TX_WAIT_FREE_SLOT_TIME (10 * HZ)
#define SMC_WR_TX_SIZE 44 /* actual size of wr_send data (<=SMC_WR_BUF_SIZE) */
--
2.48.1
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