Re: [PATCH net-next 00/15] net/smc: implement loopback-ism used by SMC-D

From: Jiri Pirko
Date: Thu Jan 11 2024 - 09:50:46 EST

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Thu, Jan 11, 2024 at 01:00:21PM CET, guwen@xxxxxxxxxxxxxxxxx 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

Care to provide more details about what ISM and intra-CPC is and what it
it good for?

>on the non-s390 architecture through a software-implemented virtual ISM device,
>that is the loopback-ism device here, to accelerate inter-process or

I see no such device. Is it a netdevice?

If it is "software-implemented", why is it part of smc driver and not
separate soft-device driver? If there is some smc specific code, I guess
there should be some level of separation. Can't this be implemented by
other devices too?

>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?

> 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@xxxxxxxxxxxxxxxxx/
>- 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@xxxxxxxxxxxxxxxxx/
>[2] https://lore.kernel.org/netdev/20231219142616.80697-1-guwen@xxxxxxxxxxxxxxxxx/
>[3] https://github.com/goldsborough/ipc-bench
>[4] https://lore.kernel.org/all/3189e342-c38f-6076-b730-19a6efd732a5@xxxxxxxxxxxxxxxxx/
>[5] https://lore.kernel.org/all/238e63cd-e0e8-4fbf-852f-bc4d5bc35d5a@xxxxxxxxxxxxxxxxx/
>[6] https://lore.kernel.org/all/20240102184633.748113-1-urezki@xxxxxxxxx/
>
>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
>
>

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