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Message-ID: <76b53c2d-5596-44da-b759-e5e94571d401@linux.ibm.com>
Date: Fri, 16 Feb 2024 15:09:42 +0100
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Subject: Re: [PATCH net-next 00/15] net/smc: implement loopback-ism used by
 SMC-D
Content-Language: en-GB
To: Wen Gu <guwen@linux.alibaba.com>, wintera@linux.ibm.com, hca@linux.ibm.com,
        gor@linux.ibm.com, agordeev@linux.ibm.com, davem@davemloft.net,
        edumazet@google.com, kuba@kernel.org, pabeni@redhat.com,
        jaka@linux.ibm.com, Gerd Bayer <gbayer@linux.ibm.com>
Cc: borntraeger@linux.ibm.com, svens@linux.ibm.com, alibuda@linux.alibaba.com,
        tonylu@linux.alibaba.com, linux-s390@vger.kernel.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20240111120036.109903-1-guwen@linux.alibaba.com>
From: Wenjia Zhang <wenjia@linux.ibm.com>
In-Reply-To: <20240111120036.109903-1-guwen@linux.alibaba.com>
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On 11.01.24 13:00, Wen Gu wrote:
> 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 virtual 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-#2: some prepare work for loopback-ism.
>   - Patch #3-#9: implement loopback-ism device.
>   - Patch #10-#15: memory copy optimization for loopback scenario.
> 
> The loopback-ism device is designed as a 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.
>        - /sys/devices/virtual/smc/loopback-ism/dmb_copy is set to default 0,
>          which means sndbuf and DMB are merged and no data copied between them.
>        - /sys/devices/virtual/smc/loopback-ism/dmb_type is set to default 0,
>          which means DMB is physically contiguous buffer.
> 
>   * Test object:
>        - TCP: run on TCP loopback.
>        - SMC lo: run on SMC loopback device.
> 
> 1. ipc-benchmark (see [3])
> 
>   - ./<foo> -c 1000000 -s 100
> 
>                              TCP                  SMC-lo
> Message
> rate (msg/s)              80636                  149515(+85.42%)
> 
> 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)         4909.36                 8197.57(+66.98%)
> Latency(us)               6.098                   3.383(-44.52%)
> 
> 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           181685.74                246447.77(+35.65%)
> 
> 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)       85855.34                118553.64(+38.09%)
> SET(Requests/s)       86824.40                125944.58(+45.06%)
> 
> 
> Change log:
> 
> v1->RFC:
> - 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 (15):
>    net/smc: improve SMC-D device dump for virtual ISM
>    net/smc: decouple specialized struct from SMC-D DMB registration
>    net/smc: introduce virtual ISM device loopback-ism
>    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: register loopback-ism into SMC-D device list
>    net/smc: introduce loopback-ism runtime switch
>    net/smc: introduce loopback-ism statistics attributes
>    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: introduce loopback-ism DMB type control
>    net/smc: introduce loopback-ism DMB data copy control
>    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          |  58 ++-
>   net/smc/smc_cdc.h          |   1 +
>   net/smc/smc_core.c         |  61 +++-
>   net/smc/smc_core.h         |   1 +
>   net/smc/smc_ism.c          |  71 +++-
>   net/smc/smc_ism.h          |   5 +
>   net/smc/smc_loopback.c     | 718 +++++++++++++++++++++++++++++++++++++
>   net/smc/smc_loopback.h     |  88 +++++
>   13 files changed, 1026 insertions(+), 29 deletions(-)
>   create mode 100644 net/smc/smc_loopback.c
>   create mode 100644 net/smc/smc_loopback.h
> 
Hi Wen,

Thank you for the patience again!

You can find the comments under the corresponding patches respectively.
About the file hierarchy in sysfs and the names, we still have some 
thoughts. We need to investigate a bit more time on it.

Thanks,
Gerd & Wenjia