"Drivers have been made to behave when using a bigger than 128KB maximum IO transfer size"

Samuel J. Greear sjg at evilcode.net
Tue May 13 08:02:45 PDT 2014

Running up MAXPHYS will not have the same effect on DragonFly as it does on
FreeBSD, for a variety of reasons but mostly due to better optimized
read-ahead. (That is to say, DragonFly should work better out of the box).


On Tue, May 13, 2014 at 3:02 AM, Wojciech Puchar <
wojtek at wojtek.tensor.gdynia.pl> wrote:

> (x86_64/amd64) by default.
>> I experimented for a while with the ahci driver; bigger values helped to
>> increase linear (dd) performance by up to 20% with fast SSDs but it was
>> unclear
>> at the time if it would have improved regular filesystem operations.
> it should when performing parallel reads/writes on multiple large files.
> prevents seeking. in freebsd it makes enormous difference.
>> Even though all storage drivers compile fine with bigger MAXPHYS values
>> it's
>> also possible some will have issues at runtime.
>> --
>> Francois Tigeot
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