Re: large scale (audio) file I/O on OS X : help or insight requested
Re: large scale (audio) file I/O on OS X : help or insight requested
- Subject: Re: large scale (audio) file I/O on OS X : help or insight requested
- From: Hamilton Feltman <email@hidden>
- Date: Wed, 11 Mar 2015 22:10:17 -0700
On Mar 11, 2015, at 9:07 PM, Paul Davis < email@hidden> wrote:
Either something is wrong with the test, or logic is background caching. We’ve just proven that this drive can't do more than 50 tracks, with a 64kb read size. It doesn’t matter what the os is using. It is physically impossible for the drive to seek any faster when reading that blocksize. The only possiblity is that more time is being taken, i.e. background caching.
Logic is background caching as soon as the song is opened? You could test this by closing logic, clearing the file cache, opening logic and immediately starting playback while watching the trace. If it’s still reading in 64kb blocks, it’s going to stall, there are no two ways about it.
We didn’t see it in the results you posted. But this would still be a separate issue from the raw drive speeds. One possibility, if the filesystem is doing the readahead (thereby increasing the block size), it’s possible that the OS is ejecting the cached readahead pages when under memory pressure.
Regards, Hamilton
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