Increase st_blksize to 64k

Brian Ford
Tue Jan 2 19:49:00 GMT 2007

On Tue, 2 Jan 2007, Christopher Faylor wrote:

> I don't see how replacing the constant "S_BLKSIZE" with what seems to be
> an unrelated getpagesize () makes a lot of sense.

The st_blksize field represents the preferred I/O size (in bytes) for the
corresponding file system.  Generally, this is the same as, or a multiple
of the system page size for efficient cache management.  As such, I see
nothing unusual about using that function.

The following document confirms my suspicion that at least NTFS buffered
I/O is done in 64k chunks:

I believe this is a close enough parallel to the allocation granularity to
justify using it directly.

> Assuming that this is a good idea, should S_BLKSIZE be changed directly?

No, S_BLKSIZE represents the actual size of a physical block on disk,
and/or the size of the block units reported in the stat structure.
S_BLKSIZE has historically been 512 bytes.

These are actually two different things.

Brian Ford
Lead Realtime Software Engineer
VITAL - Visual Simulation Systems
FlightSafety International
the best safety device in any aircraft is a well-trained crew...

More information about the Cygwin-patches mailing list