Re: portfs and port_send_event

Yes, you‘ve hit the nail on the head - the Solaris port event framework is meant to be a more efficient substitute for semaphores and polling event completion. Sadly, its documentation leaves something to be desired.

Actually, I was wondering whether it’s possible to figure out who is posting whom by looking into the port event function parameters. In doing so, I didn‘t have any particular problem in mind, I was rather doing it just for fun, so to speak.

Meanwhile, I watched Tanel Porder‘s hacking session recording https://blog.tanelpoder.com/2018/01/11/secret-hacking-session-oracle-background-process-communication-exotic-wait-events-and-some-tracing-too/ and learned that the message exchange between processes is being captured in x$trace. Of course, this is a much better place to look for this kind of information than analyzing low level OS calls.

Best regards,

Nenad

http://nenadnoveljic.com/blog/

Von meinem iPad gesendet

> Am 14.04.2018 um 16:51 schrieb Frits Hoogland <frits.hoogland_at_gmail.com>:
>
> I am not familiar with these functions.
> It seems this port event framework is a solaris only thing, used as a substitute for semaphores, obviously because oracle thinks they have better performance or scale better. (actually they seem to say it’s mostly a substitute for polling event completion).
> There are multiple blogposts explaining them, telling essentially that.
>
> What is it that you need to know?
> port_send_event seems to send something, the address is probably a pointer to a struct, and I am quite sure a foreground that has committed is the receiver of it, because that is what the function of sskgpwpost does.
> So that would be equivalent of semop on linux, posting the semaphore on which a foreground is sleeping, waiting for the logwriter to get notified the redo write has finished.
>
> I don’t know the port event framework, but if you look at what happens when multiple processes need posting on a semaphore on linux, another function (sskgpwvectorpost) is executed and still all processes are posted serially, maybe the event framework can post them all at once. Again, I don’t know the port event framework, this might not be true, but this is the one of the problems that the port event framework is documented to solve.
>
> And the database implemented a solution for this already, which is “polling mode”, which doesn’t require any communication from the logwriter to a waiting foreground after writing, because the foreground checks writing progress itself.
>
> Frits Hoogland
>
> http://fritshoogland.wordpress.com
> frits.hoogland_at_gmail.com
> Mobile: +31 6 14180860
>

>> On 12 Apr 2018, at 10:39, Noveljic Nenad <nenad.noveljic_at_vontobel.com> wrote:
>> 
>> Is somebody familiar with the specification of Oracle Solaris kernel functions portfs and port_send_event?
>>  
>> These functions are a part of the Solaris Event Completion framework. This framework seems to be used instead of semaphores for posting messages between processes on the Solaris implementation of Oracle.
>>  
>> Here is an example of a call stack within the lgwr process:
>>  
>> port_send_event(FFFFA22B765EFBA8)
>>               libc.so.1`_portfs+0xa
>>               oracle`sskgpwpost+0xf0
>>               oracle`kslpsprns+0x19c
>>               oracle`kcrfw_slave_queue_insert+0x361
>>               oracle`kcrfw_redo_write_driver+0x73e
>>               oracle`ksbabs+0x15c4
>>               oracle`ksbrdp+0x4ce
>>               oracle`opirip+0x2cd
>>               oracle`opidrv+0x24a
>>               oracle`sou2o+0x64
>>               oracle`opimai_real+0x9f
>>               oracle`ssthrdmain+0x21d
>>               oracle`main+0x94
>>               oracle`0xabcb95b
>>  
>> While the other port_* functions are well documented (see https://docs.oracle.com/cd/E86824_01/html/E54766/port-send-3c.html#scrolltoc ) these two are completely missing despite being heavily used.
>>  
>> Best regards,
>>  
>> Nenad
>>  
>> http://nenadnoveljic.com/blog/
>>  
>>  
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