RE: [Firebird-devel] Code Cleanup SUPERSERVER_V2

[Blas R. S. <bl...@pu...>]

Hello

At 01/02/2003 17:16 +0300, Dmitry Yemanov wrote:
>Blas,
>
>> Perhaps we are talking about different thinks. I understand
>> that synchronous io means that the writing method does not
>> return until the data is send to the disk device, whether in
>> asynchronous mode the write method returns as soon as the OS
>> take the information, usually to put in some kind of cache.
>
>I was talking about async operations from the server's POV, i.e. when API
>routines return immediately after putting the I/O request to the OS queue
>(i.e. deferred I/O). After that the server should wait for event to be sure
>the data is written somewhere. This is supported only in SS_V2. You were
>talking about system level synchronization, when the data are either on disk
>or somewhere in the way. This is obviously related to all this "forced
>writes" talk. Yep, a bit different things.

OK. But it seems SUPERSERVER_V2 needs low level synchronous io operations to work.

I make a comparison between winnt.cpp and unix.cpp and I found some relations between low level syncronization and SUPERSERVER_V2 switch.

For instance, PIO_force_write in unix.cpp works only if not SUPERSERVER_V2 and in winnt.cpp works always. The comment in unix.cpp say that SUPERSERVER_V2 works always in synchronous mode so "forced_writes" is a no-op. What happen in winnt?.

As you can see forced writes and SUPERSERVER_V2 are related in the code, although perhaps it can be isolated in the theory.

I think winnt.cpp and unix.cpp code must be synchronized :-) the two sources don't need to be so different. I think things will easier if  windows and *nix works in the same or similar way.

Regards
Blas Rodriguez Somoza