From 3ac14b9dfbd345e891d48d89f6c2fa519848f0f4 Mon Sep 17 00:00:00 2001 From: Guangguan Wang Date: Mon, 3 Jun 2024 11:00:18 +0800 Subject: [PATCH 1/2] net/smc: set rmb's SG_MAX_SINGLE_ALLOC limitation only when CONFIG_ARCH_NO_SG_CHAIN is defined 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 Co-developed-by: Wen Gu Signed-off-by: Wen Gu Signed-off-by: David S. Miller --- 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; } From 2f4b101c542e102c680d136fc6dca081e3fbda4a Mon Sep 17 00:00:00 2001 From: Guangguan Wang Date: Mon, 3 Jun 2024 11:00:19 +0800 Subject: [PATCH 2/2] net/smc: change SMCR_RMBE_SIZES from 5 to 15 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 Co-developed-by: Wen Gu Signed-off-by: Wen Gu Signed-off-by: David S. Miller --- 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.