On 2024/2/23 22:13, Wenjia Zhang wrote:
On 20.02.24 03:45, Wen Gu wrote:
On 2024/2/16 22:24, Wenjia Zhang wrote:
On 11.01.24 13:00, Wen Gu wrote:
This introduces some statistics attributes of loopback-ism. They can be
read from /sys/devices/virtual/smc/loopback-ism/{xfer_tytes|dmbs_cnt}.
Signed-off-by: Wen Gu <guwen@xxxxxxxxxxxxxxxxx>
---
net/smc/smc_loopback.c | 74 ++++++++++++++++++++++++++++++++++++++++++
net/smc/smc_loopback.h | 22 +++++++++++++
2 files changed, 96 insertions(+)
I've read the comments from Jiri and your answer. I can understand your thought. However, from the perspective of the
end user, it makes more sense to integetrate the stats info into 'smcd stats'. Otherwise, it would make users
confused to find out with which tool to check which statisic infornation. Sure, some improvement of the smc-tools is
also needed
Thank you Wenjia.
Let's draw an analogy with RDMA devices, which is used in SMC-R. If we want
to check the RNIC status or statistics, we may use rdma statistic command, or
ibv_devinfo command, or check file under /sys/class/infiniband/mlx5_0. These
provide details or attributes related to *devices*.
Since s390 ISM can be used out of SMC, I guess it also has its own way (other
than smc-tools) to check the statistic?
What we can see in smcr stats or smcd stats command is about statistic or
status of SMC *protocol* layer, such as DMB status, Tx/Rx, connections, fallbacks.
If we put the underlying devices's statistics into smc-tools, should we also
put RNIC statistics or s390 ISM statistics into smcr stat or smcd stat? and
for each futures device that can be used by SMC-R/SMC-D, should we update them
into smcr stat and smcd stat? And the attributes of each devices may be different,
should we add entries in smcd stat for each of them?
After considering the above things, I believe that the details of the underlying
device should not be exposed to smc(smc-tools). What do you think?
Thanks!
That is a very good point. It really depends on how we understand *devices* and how we want to use it. The more we are
thinking, the more complicated the thing is getting. I'm trying to find accurate definitions on modeling virtual devices
hoping that would make things eaiser. Unfortunately, it is not easy. Finally, I found this article:
https://lwn.net/Articles/645810/ (Heads up! It is even from nine years ago, I'm not sure how reliable it is.) With the
insight of this article, I'm trying to summarize my thought:
It looks good to put the loopback-ism under the /sys/devices/virtual, especially according to the article
"
... it is simply a place to put things that don't belong anywhere else.
"
Yes, it can also be reflected from the implementation of get_device_parent():
static struct kobject *get_device_parent(struct device *dev,
struct device *parent)
{
<...>
/*
* If we have no parent, we live in "virtual".
* Class-devices with a non class-device as parent, live
* in a "glue" directory to prevent namespace collisions.
*/
if (parent == NULL)
parent_kobj = virtual_device_parent(dev);
else if (parent->class && !dev->class->ns_type) {
subsys_put(sp);
return &parent->kobj;
} else {
parent_kobj = &parent->kobj;
}
<...>
}
However, in practice we use this in the term of simulated ism, which includes not only loopback-ism, but also other
ones. Thus, does it not make sense to classify all of them together? E.g. same bus (just a half-baked idea)
Then the following questions are comig up:
- How should we organize them?
- Should it show up in the smc_rnics?
- How should it be seen from the perspective of the container?
- If we see this loopback-ism as a *device*, should we not only put the device related information under the /sys? Thus,
dmbs_cnt seems ok, but xfer_tytes not. Besides, we have a field in smd stat naming "Data transmitted (Bytes)", which
should be suitable for this information.
Actually I created 'smc' class under /sys/devices/virtual just to place
loopback-ism, since it doesn't seem to belong to a certain class of device
and serves only SMC. Other 'smc devices', e.g. RDMA device, s390 ISM and
other Emulated-ISM like virtio-ism, all belong to a certain class or bus,
so I have no intention of putting them under the same path.
But now looks like that the 'smc' class and /sys/devices/virtual/smc path
will lead people to mistakenly think that there is a class of 'SMC devices',
but in fact these 'SMC devices' belongs to different classes or buses. They
can be used by SMC and any other users. So I think it is better to avoid
creating such 'smc' class.
Alternatively, after referring to other examples in the kernel, I think
another choice is to to put loopback-ism under /sys/devices/virtual/misc/,
for devices which can't fit in a specific class. What do you think?
Thanks a lot!
