> Oleg Bartunov wrote:
>>On Wed, 27 Feb 2002, mlw wrote:
[Greg's ramblings removed]
>>do you consider to work on this issue ?
> Yea, let me think about it. What is your time frame? When I offered to work on
> it, I thought it could be a leasurely thing. I have to get a machine running
> some form of Windows on which to develop and test.
> I want to say yes, and if no one else does it, I will, but I'm not sure what
> your timeframe is. If it is the mystical 7.3, then sure I can do it easily. If
> you need something quickly, I can help, but I don't think I could shoulder the
> whole thing.
It appears that cygipc's shared memory implementation boils down to
pretty much this section of code. As extracted from shm_connect in shm.c:
GFdShm = open(CYGWIN_IPCNT_FILESHM, O_RDWR, 00666 ) ;
shareadrshm = (CYGWIN_IPCNT_SHMSTR *)
mmap(0, sizeof(CYGWIN_IPCNT_SHMSTR), PROT_WRITE|PROT_READ,
MAP_SHARED, GFdShm, 0) ;
if( shareadrshm == (CYGWIN_IPCNT_SHMSTR *) -1 )
close (GFdShm) ;
return (0) ;
So, I guess the question of the day is, how is Cygwin handling mmap()
Perhaps looking to see if Cygwin can support page file access via
INVALID_HANDLE_VALUE to the *assumed* CreateFileMapping call?? I get
the impression that you already understand this, however, I thought I'd
go ahead and toss this out there. By using the INVALID_HANDLE_VALUE
(0xFFFFFFFF) value during's initial mapped file's creation, it is
actually being backed by the VM's page file rather than a distinct file
layered on top of the FS.
As you said earlier, this may provide for less disk contension, however,
I'm doubtful you're going to find a significant speed improvement. Just
the same, I guess a couple percent here and there can add up.
In case you can't tell, I'm somewhat interested in this thread. When
you get ready to do the implementation, I wouldn't mind kicking the code
around a little. Of course, being that pesky voice that says, "what
about this..." can just be plain fun too. ;)
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