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Wen Gu says: ==================== net/smc: SMC intra-OS shortcut with loopback-ism This patch set acts as the second part of the new version of [1] (The first part can be referred from [2]), the updated things of this version are listed at the end. - Background SMC-D is now used in IBM z with ISM function to optimize network interconnect for intra-CPC communications. Inspired by this, we try to make SMC-D available on the non-s390 architecture through a software-implemented Emulated-ISM device, that is the loopback-ism device here, to accelerate inter-process or inter-containers communication within the same OS instance. - Design This patch set includes 3 parts: - Patch #1: some prepare work for loopback-ism. - Patch #2-#7: implement loopback-ism device and adapt SMC-D for it. loopback-ism now serves only SMC and no userspace interfaces exposed. - Patch #8-#11: memory copy optimization for intra-OS scenario. The loopback-ism device is designed as an ISMv2 device and not be limited to a specific net namespace, ends of both inter-process connection (1/1' in diagram below) or inter-container connection (2/2' in diagram below) can find the same available loopback-ism and choose it during the CLC handshake. Container 1 (ns1) Container 2 (ns2) +-----------------------------------------+ +-------------------------+ | +-------+ +-------+ +-------+ | | +-------+ | | | App A | | App B | | App C | | | | App D |<-+ | | +-------+ +---^---+ +-------+ | | +-------+ |(2') | | |127.0.0.1 (1')| |192.168.0.11 192.168.0.12| | | (1)| +--------+ | +--------+ |(2) | | +--------+ +--------+ | | `-->| lo |-` | eth0 |<-` | | | lo | | eth0 | | +---------+--|---^-+---+-----|--+---------+ +-+--------+---+-^------+-+ | | | | Kernel | | | | +----+-------v---+-----------v----------------------------------+---+----+ | | TCP | | | | | | | +--------------------------------------------------------------+ | | | | +--------------+ | | | smc loopback | | +---------------------------+--------------+-----------------------------+ loopback-ism device creates DMBs (shared memory) for each connection peer. Since data transfer occurs within the same kernel, the sndbuf of each peer is only a descriptor and point to the same memory region as peer DMB, so that the data copy from sndbuf to peer DMB can be avoided in loopback-ism case. Container 1 (ns1) Container 2 (ns2) +-----------------------------------------+ +-------------------------+ | +-------+ | | +-------+ | | | App C |-----+ | | | App D | | | +-------+ | | | +-^-----+ | | | | | | | | (2) | | | (2') | | | | | | | | +---------------|-------------------------+ +----------|--------------+ | | Kernel | | +---------------|-----------------------------------------|--------------+ | +--------+ +--v-----+ +--------+ +--------+ | | |dmb_desc| |snd_desc| |dmb_desc| |snd_desc| | | +-----|--+ +--|-----+ +-----|--+ +--------+ | | +-----|--+ | +-----|--+ | | | DMB C | +---------------------------------| DMB D | | | +--------+ +--------+ | | | | +--------------+ | | | smc loopback | | +---------------------------+--------------+-----------------------------+ - Benchmark Test * Test environments: - VM with Intel Xeon Platinum 8 core 2.50GHz, 16 GiB mem. - SMC sndbuf/DMB size 1MB. * Test object: - TCP: run on TCP loopback. - SMC lo: run on SMC loopback-ism. 1. ipc-benchmark (see [3]) - ./<foo> -c 1000000 -s 100 TCP SMC-lo Message rate (msg/s) 84991 151293(+78.01%) 2. sockperf - serv: <smc_run> sockperf sr --tcp - clnt: <smc_run> sockperf { tp | pp } --tcp --msg-size={ 64000 for tp | 14 for pp } -i 127.0.0.1 -t 30 TCP SMC-lo Bandwidth(MBps) 5033.569 7987.732(+58.69%) Latency(us) 5.986 3.398(-43.23%) 3. nginx/wrk - serv: <smc_run> nginx - clnt: <smc_run> wrk -t 8 -c 1000 -d 30 http://127.0.0.1:80 TCP SMC-lo Requests/s 187951.76 267107.90(+42.12%) 4. redis-benchmark - serv: <smc_run> redis-server - clnt: <smc_run> redis-benchmark -h 127.0.0.1 -q -t set,get -n 400000 -c 200 -d 1024 TCP SMC-lo GET(Requests/s) 86132.64 118133.49(+37.15%) SET(Requests/s) 87374.40 122887.86(+40.65%) Change log: v7->v6 - Patch #2: minor: remove unnecessary 'return' of inline smc_loopback_exit(). - Patch #10: minor: directly return 0 instead of 'rc' in smcd_cdc_msg_send(). - all: collect the Reviewed-by tags. v6->RFC v5 Link: https://lore.kernel.org/netdev/20240414040304.54255-1-guwen@linux.alibaba.com/ - Patch #2: make the use of CONFIG_SMC_LO cleaner. - Patch #5: mark some smcd_ops that loopback-ism doesn't support as optional and check for the support when they are called. - Patch #7: keep loopback-ism at the beginning of the SMC-D device list. - Some expression changes in commit logs and comments. RFC v5->RFC v4: Link: https://lore.kernel.org/netdev/20240324135522.108564-1-guwen@linux.alibaba.com/ - Patch #2: minor changes in description of config SMC_LO and comments. - Patch #10: minor changes in comments and if(smc_ism_support_dmb_nocopy()) check in smcd_cdc_msg_send(). - Patch #3: change smc_lo_generate_id() to smc_lo_generate_ids() and SMC_LO_CHID to SMC_LO_RESERVED_CHID. - Patch #5: memcpy while holding the ldev->dmb_ht_lock. - Some expression changes in commit logs. RFC v4->v3: Link: https://lore.kernel.org/netdev/20240317100545.96663-1-guwen@linux.alibaba.com/ - The merge window of v6.9 is open, so post this series as an RFC. - Patch #6: since some information fed back by smc_nl_handle_smcd_dev() dose not apply to Emulated-ISM (including loopback-ism here), loopback-ism is not exposed through smc netlink for the time being. we may refactor this part when smc netlink interface is updated. v3->v2: Link: https://lore.kernel.org/netdev/20240312142743.41406-1-guwen@linux.alibaba.com/ - Patch #11: use tasklet_schedule(&conn->rx_tsklet) instead of smcd_cdc_rx_handler() to avoid possible recursive locking of conn->send_lock and use {read|write}_lock_bh() to acquire dmb_ht_lock. v2->v1: Link: https://lore.kernel.org/netdev/20240307095536.29648-1-guwen@linux.alibaba.com/ - All the patches: changed the term virtual-ISM to Emulated-ISM as defined by SMCv2.1. - Patch #3: optimized the description of SMC_LO config. Avoid exposing loopback-ism to sysfs and remove all the knobs until future definition clear. - Patch #3: try to make lockdep happy by using read_lock_bh() in smc_lo_move_data(). - Patch #6: defaultly use physical contiguous DMB buffers. - Patch #11: defaultly enable DMB no-copy for loopback-ism and free the DMB in unregister_dmb or detach_dmb when dmb_node->refcnt reaches 0, instead of using wait_event to keep waiting in unregister_dmb. v1->RFC: Link: https://lore.kernel.org/netdev/20240111120036.109903-1-guwen@linux.alibaba.com/ - Patch #9: merge rx_bytes and tx_bytes as xfer_bytes statistics: /sys/devices/virtual/smc/loopback-ism/xfer_bytes - Patch #10: add support_dmb_nocopy operation to check if SMC-D device supports merging sndbuf with peer DMB. - Patch #13 & #14: introduce loopback-ism device control of DMB memory type and control of whether to merge sndbuf and DMB. They can be respectively set by: /sys/devices/virtual/smc/loopback-ism/dmb_type /sys/devices/virtual/smc/loopback-ism/dmb_copy The motivation for these two control is that a performance bottleneck was found when using vzalloced DMB and sndbuf is merged with DMB, and there are many CPUs and CONFIG_HARDENED_USERCOPY is set [4]. The bottleneck is caused by the lock contention in vmap_area_lock [5] which is involved in memcpy_from_msg() or memcpy_to_msg(). Currently, Uladzislau Rezki is working on mitigating the vmap lock contention [6]. It has significant effects, but using virtual memory still has additional overhead compared to using physical memory. So this new version provides controls of dmb_type and dmb_copy to suit different scenarios. - Some minor changes and comments improvements. RFC->old version([1]): Link: https://lore.kernel.org/netdev/1702214654-32069-1-git-send-email-guwen@linux.alibaba.com/ - Patch #1: improve the loopback-ism dump, it shows as follows now: # smcd d FID Type PCI-ID PCHID InUse #LGs PNET-ID 0000 0 loopback-ism ffff No 0 - Patch #3: introduce the smc_ism_set_v2_capable() helper and set smc_ism_v2_capable when ISMv2 or virtual ISM is registered, regardless of whether there is already a device in smcd device list. - Patch #3: loopback-ism will be added into /sys/devices/virtual/smc/loopback-ism/. - Patch #8: introduce the runtime switch /sys/devices/virtual/smc/loopback-ism/active to activate or deactivate the loopback-ism. - Patch #9: introduce the statistics of loopback-ism by /sys/devices/virtual/smc/loopback-ism/{{tx|rx}_tytes|dmbs_cnt}. - Some minor changes and comments improvements. [1] https://lore.kernel.org/netdev/1695568613-125057-1-git-send-email-guwen@linux.alibaba.com/ [2] https://lore.kernel.org/netdev/20231219142616.80697-1-guwen@linux.alibaba.com/ [3] https://github.com/goldsborough/ipc-bench [4] https://lore.kernel.org/all/3189e342-c38f-6076-b730-19a6efd732a5@linux.alibaba.com/ [5] https://lore.kernel.org/all/238e63cd-e0e8-4fbf-852f-bc4d5bc35d5a@linux.alibaba.com/ [6] https://lore.kernel.org/all/20240102184633.748113-1-urezki@gmail.com/ ==================== Link: https://lore.kernel.org/r/20240428060738.60843-1-guwen@linux.alibaba.com Signed-off-by: Paolo Abeni <pabeni@redhat.com>
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