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. 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: Frits Hoogland <frits.hoogland@xxxxxxxxx<mailto:frits.hoogland@xxxxxxxxx>>
Datum Samstag, 14. Apr. 2018, 4:51 PM
An: Noveljic Nenad
<nenad.noveljic@xxxxxxxxxxxx<mailto:nenad.noveljic@xxxxxxxxxxxx>>
Cc: ORACLE-L (oracle-l@xxxxxxxxxxxxx)
<oracle-l@xxxxxxxxxxxxx<mailto:oracle-l@xxxxxxxxxxxxx>>
Betreff: Re: portfs and port_send_event
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<http://fritshoogland.wordpress.com/>
frits.hoogland@xxxxxxxxx<mailto:frits.hoogland@xxxxxxxxx>
Mobile: +31 6 14180860
On 12 Apr 2018, at 10:39, Noveljic Nenad
<nenad.noveljic@xxxxxxxxxxxx<mailto:nenad.noveljic@xxxxxxxxxxxx>> 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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