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Date: Fri, 12 Jan 2024 16:50:01 +0100
From: Jiri Pirko <jiri@...nulli.us>
To: Wen Gu <guwen@...ux.alibaba.com>
Cc: wintera@...ux.ibm.com, wenjia@...ux.ibm.com, hca@...ux.ibm.com,
gor@...ux.ibm.com, agordeev@...ux.ibm.com, davem@...emloft.net,
edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
jaka@...ux.ibm.com, borntraeger@...ux.ibm.com, svens@...ux.ibm.com,
alibuda@...ux.alibaba.com, tonylu@...ux.alibaba.com,
linux-s390@...r.kernel.org, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 00/15] net/smc: implement loopback-ism used by
SMC-D
Fri, Jan 12, 2024 at 01:32:14PM CET, guwen@...ux.alibaba.com wrote:
>
>
>On 2024/1/12 17:10, Jiri Pirko wrote:
>> Fri, Jan 12, 2024 at 09:29:35AM CET, guwen@...ux.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
>> > > >
>> > > >
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