Re: High bandwidth disk management techniques
Re: High bandwidth disk management techniques
- Subject: Re: High bandwidth disk management techniques
- From: kelly jacklin <email@hidden>
- Date: Mon, 2 May 2005 06:36:55 -0700
This is not at all surprising, as each thread is issuing reads which
compete for the scheduling resources of the disk.
When working on filesystem performance issues, at one point we
experimented around with the CpMac tool to do various threaded
models. The one that we found worked best was to single-thread all
access to files on volumes corresponding to the same _physical_
device, but to have separate threads for each physical device we
encountered.
This was some time ago, back in early 10.2 development, so things
might have changed, and there may be more smarts in the disk
scheduler nowadays, I do not know. If not, then you might take this
approach as well.
kelly
On May 2, 2005, at 5:47 AM, philippe wicker wrote:
Some times ago (OS X 10.2.x) I tried to bench the simultaneous disk
accesses to a number of files. For the little story, these files
were 25 MBytes segment of a MacOS X update. I did that using two
methods. The first one was to sequentially access a 64KByte chunk
in each file. The second method was to trigger the access to each
file in a different thread (one thread dedicated to a given number
of files), this method is a variant of multiple asynchronous reads.
The results were really surprising and unexpected (at least for
me): the "threaded" access gave a twice worse - yes worse -
performance on the internal drive than the "sequential" method, and
an equivalent result on an external FW400 drive.
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Coreaudio-api mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden