On Wed, 2007-04-04 at 13:29 -0500, Jon Nelson wrote: > On Wed, 4 Apr 2007, Bill Anderson wrote: > > > I noticed that the default elevator applies to everything, including USB > > memory sticks. I thought the block device driver would change the I/O > > scheduler to something more appropriate for a memory stick, such as the noop > > scheduler. I switched to the noop scheduler for just the memory stick, and > > there was an improvement in performance. I haven't done a detailed > > statistical > > analysis to verify my empirical impression. > > > > I have a few questions: > > 1) Is there a reason for the block device driver not changing the I/O > > scheduler to noop? > > 2) How do I modify HAL to change the I/O scheduler when it detects that a > > hotplug for a memory stick? > > I can't answer (1), and (2) is probably pretty easy. > However, let me offer an alternative: > > set the *default* I/O scheduler (there /are/ several schedulers, you > know) to noop and then at boot time re-set your HDD (or whatever local > devices you want to change back) to "anticipatory" (or whatever you > use).
Perhaps this is related to an issue I am starting to look in to. I have a system with a number of PCI I/O cards (firewire, video, SCSI, network) as well as the good old serial ports (16550-based - not PCI). In some system loads (not excessive) I see that the serial port driver starts to report data overruns. I also see missing characters in GPS data read over the serial port at this time. I am trying to see why these overruns are happening. The serial port is operating at 38400. The 16550 can only buffer 16 characters in hardware. So the device driver must service the hardware within that time or data will be lost (handshake issues aside - eventually some buffer can get full). Could it be that some device driver has a higher priority and is blocking the serial port driver from servicing the hardware? I am running whatever default priorities are in SUSE 10.0. Am I looking in the right direction?. -- Roger Oberholtzer OPQ Systems / Ramböll RST Ramböll Sverige AB Kapellgränd 7 P.O. Box 4205 SE-102 65 Stockholm, Sweden Tel: Int +46 8-615 60 20 Fax: Int +46 8-31 42 23 -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
