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Re: Increase st_blksize to 64k
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:
http://research.microsoft.com/BARC/Sequential_IO/seqio.doc
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...