What version of protobuf and what language are you using?
Version: 3.18.0
Language: Python (version 3.7.0)

What operating system (Linux, Windows, ...) and version?
gLinux

What did you do?
Run the below script using protobuf version 3.17.3 then run it again using protobuf version 3.18.0 and compare the results. I ran this 30 times per version, each in a fresh python interpreter, and compared the averages.

import proto
from time import time
 
 
class ProtoPlusFixture(proto.Message):
    name = proto.Field(proto.STRING, number=1)
 
init_start = time()
pplus = ProtobufFixture()
init = time() - init_start
 
set_start = time()
pplus.name = "Test"
set_time = time() - set_start
 
print(f"{init * 1000}, {set_time * 1000}")

What did you expect to see
I expect to see the performance to be similar for each version.

What did you see instead?

• 3.18.0 class init avg. = 0.005571047465
• 3.17.3 class init avg. = 0.004593531291
• 3.18.0 field set avg. = 0.02173582713
• 3.17.3 field set avg. = 0.01894632975

That is a 21% regression in class initialization and a 14% regression when setting fields.

Anything else we should know about your project / environment

We have an internal performance framework that shows that these regressions are significant at a larger scale as well, (i.e. reading and writing several fields, processing larger requests with nested fields) and we began seeing degradations around the time that 3.18.0 was published.