SMCR_RMBE_SIZES is the upper boundary of SMC-R's snd_buf and rcv_buf.
The maximum bytes of snd_buf and rcv_buf can be calculated by 2^SMCR_
RMBE_SIZES * 16KB. SMCR_RMBE_SIZES = 5 means the upper boundary is 512KB.
TCP's snd_buf and rcv_buf max size is configured by net.ipv4.tcp_w/rmem[2]
whose default value is 4MB or 6MB, is much larger than SMC-R's upper
boundary.
In some scenarios, such as Recommendation System, the communication
pattern is mainly large size send/recv, where the size of snd_buf and
rcv_buf greatly affects performance. Due to the upper boundary
disadvantage, SMC-R performs poor than TCP in those scenarios. So it
is time to enlarge the upper boundary size of SMC-R's snd_buf and rcv_buf,
so that the SMC-R's snd_buf and rcv_buf can be configured to larger size
for performance gain in such scenarios.
The SMC-R rcv_buf's size will be transferred to peer by the field
rmbe_size in clc accept and confirm message. The length of the field
rmbe_size is four bits, which means the maximum value of SMCR_RMBE_SIZES
is 15. In case of frequently adjusting the value of SMCR_RMBE_SIZES
in different scenarios, set the value of SMCR_RMBE_SIZES to the maximum
value 15, which means the upper boundary of SMC-R's snd_buf and rcv_buf
is 512MB. As the real memory usage is determined by the value of
net.smc.w/rmem, not by the upper boundary, set the value of SMCR_RMBE_SIZES
to the maximum value has no side affects.
Guangguan Wang (2):
net/smc: set rmb's SG_MAX_SINGLE_ALLOC limitation only when
CONFIG_ARCH_NO_SG_CHAIN is defined
net/smc: change SMCR_RMBE_SIZES from 5 to 15
net/smc/smc_core.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
--
2.24.3 (Apple Git-128)
SMCR_RMBE_SIZES is the upper boundary of SMC-R's snd_buf and rcv_buf.
The maximum bytes of snd_buf and rcv_buf can be calculated by 2^SMCR_
RMBE_SIZES * 16KB. SMCR_RMBE_SIZES = 5 means the upper boundary is 512KB.
TCP's snd_buf and rcv_buf max size is configured by net.ipv4.tcp_w/rmem[2]
whose default value is 4MB or 6MB, is much larger than SMC-R's upper
boundary.
In some scenarios, such as Recommendation System, the communication
pattern is mainly large size send/recv, where the size of snd_buf and
rcv_buf greatly affects performance. Due to the upper boundary
disadvantage, SMC-R performs poor than TCP in those scenarios. So it
is time to enlarge the upper boundary size of SMC-R's snd_buf and rcv_buf,
so that the SMC-R's snd_buf and rcv_buf can be configured to larger size
for performance gain in such scenarios.
The SMC-R rcv_buf's size will be transferred to peer by the field
rmbe_size in clc accept and confirm message. The length of the field
rmbe_size is four bits, which means the maximum value of SMCR_RMBE_SIZES
is 15. In case of frequently adjusting the value of SMCR_RMBE_SIZES
in different scenarios, set the value of SMCR_RMBE_SIZES to the maximum
value 15, which means the upper boundary of SMC-R's snd_buf and rcv_buf
is 512MB. As the real memory usage is determined by the value of
net.smc.w/rmem, not by the upper boundary, set the value of SMCR_RMBE_SIZES
to the maximum value has no side affects.
Signed-off-by: Guangguan Wang <[email protected]>
Co-developed-by: Wen Gu <[email protected]>
Signed-off-by: Wen Gu <[email protected]>
---
net/smc/smc_core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
index acca3b1a068f..3b95828d9976 100644
--- a/net/smc/smc_core.c
+++ b/net/smc/smc_core.c
@@ -2006,7 +2006,7 @@ int smc_conn_create(struct smc_sock *smc, struct smc_init_info *ini)
}
#define SMCD_DMBE_SIZES 6 /* 0 -> 16KB, 1 -> 32KB, .. 6 -> 1MB */
-#define SMCR_RMBE_SIZES 5 /* 0 -> 16KB, 1 -> 32KB, .. 5 -> 512KB */
+#define SMCR_RMBE_SIZES 15 /* 0 -> 16KB, 1 -> 32KB, .. 15 -> 512MB */
/* convert the RMB size into the compressed notation (minimum 16K, see
* SMCD/R_DMBE_SIZES.
--
2.24.3 (Apple Git-128)
SG_MAX_SINGLE_ALLOC is used to limit maximum number of entries that
will be allocated in one piece of scatterlist. When the entries of
scatterlist exceeds SG_MAX_SINGLE_ALLOC, sg chain will be used. From
commit 7c703e54cc71 ("arch: switch the default on ARCH_HAS_SG_CHAIN"),
we can know that the macro CONFIG_ARCH_NO_SG_CHAIN is used to identify
whether sg chain is supported. So, SMC-R's rmb buffer should be limited
by SG_MAX_SINGLE_ALLOC only when the macro CONFIG_ARCH_NO_SG_CHAIN is
defined.
Fixes: a3fe3d01bd0d ("net/smc: introduce sg-logic for RMBs")
Signed-off-by: Guangguan Wang <[email protected]>
Co-developed-by: Wen Gu <[email protected]>
Signed-off-by: Wen Gu <[email protected]>
---
net/smc/smc_core.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
index fafdb97adfad..acca3b1a068f 100644
--- a/net/smc/smc_core.c
+++ b/net/smc/smc_core.c
@@ -2015,7 +2015,6 @@ int smc_conn_create(struct smc_sock *smc, struct smc_init_info *ini)
*/
static u8 smc_compress_bufsize(int size, bool is_smcd, bool is_rmb)
{
- const unsigned int max_scat = SG_MAX_SINGLE_ALLOC * PAGE_SIZE;
u8 compressed;
if (size <= SMC_BUF_MIN_SIZE)
@@ -2025,9 +2024,11 @@ static u8 smc_compress_bufsize(int size, bool is_smcd, bool is_rmb)
compressed = min_t(u8, ilog2(size) + 1,
is_smcd ? SMCD_DMBE_SIZES : SMCR_RMBE_SIZES);
+#ifdef CONFIG_ARCH_NO_SG_CHAIN
if (!is_smcd && is_rmb)
/* RMBs are backed by & limited to max size of scatterlists */
- compressed = min_t(u8, compressed, ilog2(max_scat >> 14));
+ compressed = min_t(u8, compressed, ilog2((SG_MAX_SINGLE_ALLOC * PAGE_SIZE) >> 14));
+#endif
return compressed;
}
--
2.24.3 (Apple Git-128)
Hello:
This series was applied to netdev/net-next.git (main)
by David S. Miller <[email protected]>:
On Mon, 3 Jun 2024 11:00:17 +0800 you wrote:
> SMCR_RMBE_SIZES is the upper boundary of SMC-R's snd_buf and rcv_buf.
> The maximum bytes of snd_buf and rcv_buf can be calculated by 2^SMCR_
> RMBE_SIZES * 16KB. SMCR_RMBE_SIZES = 5 means the upper boundary is 512KB.
> TCP's snd_buf and rcv_buf max size is configured by net.ipv4.tcp_w/rmem[2]
> whose default value is 4MB or 6MB, is much larger than SMC-R's upper
> boundary.
>
> [...]
Here is the summary with links:
- [net-next,v2,1/2] net/smc: set rmb's SG_MAX_SINGLE_ALLOC limitation only when CONFIG_ARCH_NO_SG_CHAIN is defined
https://git.kernel.org/netdev/net-next/c/3ac14b9dfbd3
- [net-next,v2,2/2] net/smc: change SMCR_RMBE_SIZES from 5 to 15
https://git.kernel.org/netdev/net-next/c/2f4b101c542e
You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html