Re: [linux-audio-dev] Performance and SCSI
Paul, I was trying to understand why the performance you get is so much better than what Benno and I get, and I'm now fairly convinced it's the hardware. Your SCSI adapters can reorder IO in order to minimize seeking, so the metadata updates when using O_SYNC don't kill performance as they do in the case of IDE drives. I wouldn't be surprised to find out that it delays writing if a read has been requested either, so you don't get big delays when bdflush runs. I'm sure that the low latencies and large buffers on your drives don't hurt any either :) The upshot of this is that for a SCSI drive, good performance is easy to get irrespective of how you do your I/O. For IDE drives, the kernel and app need to work together to try to do what the adapter is giving you automatically. Karl.
Re: [linux-audio-dev] Performance and SCSI
I was trying to understand why the performance you get is so much better than what Benno and I get, and I'm now fairly convinced it's the hardware. [ ... ] yes, but a WARNING: anyone thinking of moving to 2.3.99pre5 or above: there appears to be a serious bug that will kill ardour's performance (as well as Benno's test programs). I've posted a followup on linux-kernel to the person who first noticed it. Basically, writing a few hundred MB causes the box to slow to a crawl as memory utilization goes through the roof. This was not the case in 2.3.51. Right now, I cannot run Benno's hdtest program (it will never complete), and ardour cannot record more than a minute or so of a handful of tracks without a dropout. Again, this appears to be a new bug introduced in 2.3.99 somewhere. --p
