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Date: Fri, 12 Jan 2024 16:50:01 +0100
From: Jiri Pirko <jiri@resnulli.us>
To: Wen Gu <guwen@linux.alibaba.com>
Cc: wintera@linux.ibm.com, wenjia@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, 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
Subject: Re: [PATCH net-next 00/15] net/smc: implement loopback-ism used by
 SMC-D
Message-ID: <ZaFfqZbgpVtVt4XM@nanopsycho>
References: <20240111120036.109903-1-guwen@linux.alibaba.com>
 <ZaAAJDiQ3bPGGRFK@nanopsycho>
 <2d8e7aeb-06da-434c-b7fe-6c1bd2e0674a@linux.alibaba.com>
 <ZaEB-b-W9Jt77T98@nanopsycho>
 <d7f9684e-4115-4b04-9e92-dbb841a52935@linux.alibaba.com>
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In-Reply-To: <d7f9684e-4115-4b04-9e92-dbb841a52935@linux.alibaba.com>

Fri, Jan 12, 2024 at 01:32:14PM CET, guwen@linux.alibaba.com wrote:
>
>
>On 2024/1/12 17:10, Jiri Pirko wrote:
>> Fri, Jan 12, 2024 at 09:29:35AM CET, guwen@linux.alibaba.com wrote:
>> > 
>> > 
>
><...>
>
>> > > > 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,
>> > > 
>> > > Exposing any configuration knobs and statistics over sysfs for
>> > > softdevices does not look correct at all :/ Could you please avoid
>> > > sysfs?
>> > > 
>> > 
>> > In previous reviews and calls, we think loopback-ism needs to be more
>> > like a device and be visible under /sys/devices.
>> > 
>> > Would you mind explaining why using sysfs for loopback-ism is not correct?
>> > since I saw some other configurations or statistics exists under /sys/devices,
>> > e.g. /sys/devices/virtual/net/lo. Thank you!
>> 
>> You have smc_netlink.c exposing clear netlink api for the subsystem.
>> Can't you extend it to contain the configuration knobs and expose stats
>> instead of sysfs?
>> 
>
>Thank you for the suggestion. I've also considered this approach.
>
>But I didn't choose to extend the smc netlink because for now smc netlink
>are used for SMC protocol related attributes, for example:
>
>SMC_NETLINK_GET_SYS_INFO:     SMC version, release, v2-capable..
>SMC_NETLINK_GET_LGR_SMC{R|D}: SMC-{R|D} link group inform (lgr id, lgr conn num, lgr role..)
>SMC_NETLINK_GET_LINK_SMCR:    SMC-R link inform (link id, link state, conn cnt..)
>SMC_NETLINK_GET_DEV_SMCD:     SMC-D device generic inform (user cnt, pci_fid, pci_chid, pci_vendor..)
>SMC_NETLINK_GET_DEV_SMCR:     SMC-R device generic inform (dev name, port pnet_id, port valid, port state..)
>SMC_NETLINK_GET_STATS:        SMC generic stats (RMB cnt, Tx size, Rx size, RMB size...)
>
>And the knobs and stats in this patchset are loopback-ism device specific
>attributes, for example:
>
>active:        loopback-ism runtime switch
>dmb_type:      type of DMB provided by loopback-ism
>dmb_copy:      support for DMB merge of loopback-ism
>xfer_bytes:    data transferred by loopback-ism
>dmbs_cnt:      DMB num provided by loopback-ism
>
>The layer will be:
>
>               +--------------------------------------+
>               |                                      |
>               |             SMC protocol             |
>               |  (attrs by netlink in smc_netlink.c) |
>               |                                      |
>               +--------------------------------------+
>             ------------------smcd_ops------------------
>     +---------------+  +---------------------+  +--------------+
>     | loopback-ism  |  |  s390 firmware ISM  |  | Possible     |
>     +---------------+  |                     |  | other        |
>     (attrs by sysfs    |                     |  | virtual ISM  |
>    in smc_loopback.c)  |                     |  |              |
>                        |                     |  |              |
>                        +---------------------+  +--------------+

So nest it:
SMC_NETLINK_BACKEND_GET_INFO
SMC_NETLINK_BACKEND_GET_STATS
?
I mean, isn't it better to have the backend knobs and stats in one place
under same netlink commands and attributes than random sysfs path ?


>
>So I choose to use current way to provide this lower layer loopback-ism
>device's attributes, restrict loopback-ism specific code to smc_loopback.c
>and try to make a clear layer architecture.
>
>Thanks,
>Wen Gu
>> 
>> > 
>> > 
>> > 
>> > Thanks again,
>> > Wen Gu
>> > 
>> > > 
>> > > >          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
>> > > > 
>> > > > -- 
>> > > > 2.32.0.3.g01195cf9f
>> > > > 
>> > > >