From: David S. Miller Date: Mon, 3 Jun 2024 11:12:42 +0000 (+0100) Subject: Merge branch 'net-smc-snd_buf-rcv_buf' X-Git-Tag: io_uring-6.11-20240722~71^2~267 X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=93e30878f7ecd775cb6e1e5aeed30d947a6cebad;p=linux-block.git Merge branch 'net-smc-snd_buf-rcv_buf' Guangguan Wang says: ==================== net/smc: Change the upper boundary of SMC-R's snd_buf and rcv_buf to 512MB 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: David S. Miller --- 93e30878f7ecd775cb6e1e5aeed30d947a6cebad