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    Subject[RFC PATCH net-next v4 00/11] net/smc: SMC intra-OS shortcut with loopback-ism
    Date
    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. Noted that loopback-ism now
    serves only SMC and no userspace interface 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) 81433 143938(+76.75%)

    2. sockperf

    - serv: <smc_run> taskset -c <cpu> sockperf sr --tcp
    - clnt: <smc_run> taskset -c <cpu> sockperf { tp | pp } --tcp --msg-size={ 64000 for tp | 14 for pp } -i 127.0.0.1 -t 30

    TCP SMC-lo
    Bandwidth(MBps) 4903.07 7978.69(+62.73%)
    Latency(us) 6.095 3.539(-41.94%)

    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 161665.67 244272.41(+51.10%)

    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) 88790.23 117474.30(+32.31%)
    SET(Requests/s) 87508.20 118623.96(+35.57%)


    Change log:

    RFC v4->v3:
    - 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/

    Wen Gu (11):
    net/smc: decouple ism_client from SMC-D DMB registration
    net/smc: introduce loopback-ism for SMC intra-OS shortcut
    net/smc: implement ID-related operations of loopback-ism
    net/smc: implement some unsupported operations of loopback-ism
    net/smc: implement DMB-related operations of loopback-ism
    net/smc: ignore loopback-ism when dumping SMC-D devices
    net/smc: register loopback-ism into SMC-D device list
    net/smc: add operations to merge sndbuf with peer DMB
    net/smc: attach or detach ghost sndbuf to peer DMB
    net/smc: adapt cursor update when sndbuf and peer DMB are merged
    net/smc: implement DMB-merged operations of loopback-ism

    drivers/s390/net/ism_drv.c | 2 +-
    include/net/smc.h | 7 +-
    net/smc/Kconfig | 13 ++
    net/smc/Makefile | 2 +-
    net/smc/af_smc.c | 28 ++-
    net/smc/smc_cdc.c | 52 ++++-
    net/smc/smc_core.c | 61 ++++-
    net/smc/smc_core.h | 1 +
    net/smc/smc_ism.c | 60 ++++-
    net/smc/smc_ism.h | 10 +
    net/smc/smc_loopback.c | 462 +++++++++++++++++++++++++++++++++++++
    net/smc/smc_loopback.h | 52 +++++
    12 files changed, 724 insertions(+), 26 deletions(-)
    create mode 100644 net/smc/smc_loopback.c
    create mode 100644 net/smc/smc_loopback.h

    --
    2.32.0.3.g01195cf9f


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