I'm a bit surprised why about ~100K message size not flushing multiple
times, unless there are concurrent calls here? (using 16K frame).
Otherwise the 3 flushes per server unary should be expected if the message
isn't large.
A couple of reasons/problems I've seen:
* Write flush comes from the directly from the app's message send.
* possible fix: defer message writes to a separate writer go-routine
queue for batching (on top of other changes, seen some benefits in
streaming QPS with this)
* Must be sure that headers get sent regardless of message (
* Currently flushes after each not stuck waiting for http2 flow control
window to enlarge).
* must also be sure that steady progress is made when sending a large
message to a receiver with a small http2 flow control window.
* https://github.com/grpc/grpc-go/pull/973 addresses this by flushing
only when necessary
On Thursday, January 19, 2017 at 6:57:41 PM UTC-8, Zeymo Wang wrote:
>
>
> streaming call ,
>
> I find at least one request 3 times flush on streaming server , end header
> flush + end data flush + end status flush ,how can reduce ?
> data just less 100k,not separate data frame
>
> On Friday, January 20, 2017 at 1:33:28 AM UTC+8, apo...@google.com wrote:
>>
>> This looks like an issue that has been seen in grpc-go earlier. What
>> types of calls are these - unary? or streaming?
>>
>> Indeed for unary calls, each call is currently flushing writes after
>> sending headers and status for each call. The message portions of unary and
>> streaming calls (split up into separate http2 data frames if it's large)
>> both have some but only small amounts of batching of syscall.Writes.
>>
>> There has been some work towards reducing this but I think the issue is
>> probably somewhat expected for latest update. (There's one experimental
>> solution to reducing unary call flushes in
>> https://github.com/grpc/grpc-go/pull/973)
>>
>> On Thursday, January 19, 2017 at 1:25:36 AM UTC-8, Zeymo Wang wrote:
>>>
>>> I fork grpc-go uses as gateway just enioy h2c benifit (also remove pb
>>> IDL feature),which I implement 0-RTT TLS( cgo invoke libsodium) repalce the
>>> standard TLS and handle request just do http request to upstream; In
>>> benchmark of bidirectional streaming rpc ,high cpu usage under not much
>>> heavy load (maxConcurrencyStream = 100 or 1000 ,the same), according to "go
>>> tool pprof ", I find syscall.wirte consume much cpu and RT ( maybe cgo
>>> performance?). At least 3 time call system.wrtie (flush) will cause this
>>> problem (header + data + status)?Is orignal grpc have this issue?how to
>>> resolve or reduce invoke syscall.write？or waiting go add syscall.writev?
>>>
>>>
>>> <https://lh3.googleusercontent.com/-0TCAcilsguw/WICDnBBHKBI/AAAAAAAAB_k/2OtJVaBq9ykgXPKboM43S8PWR1OXT59oQCEw/s1600/perf.jpg>
>>>
>>>
>>> <https://lh3.googleusercontent.com/-2HXrQl6GgH0/WICENZODGQI/AAAAAAAAB_o/VUTPcgod4wQsI8Csoh7rVSBwcEe-n3yqQCLcB/s1600/strace.jpg>
>>>
>>>
>>>
>>>
>>> <https://lh3.googleusercontent.com/-IV3cZmIFYso/WICD8niuwnI/AAAAAAAAB_g/liXcah0inB4RQJxujk57SYxfzmjaVCvgQCEw/s1600/pprof.png>
>>>
>>>
>>>
>>>
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