Re: Serial Console and Slow SCSI Disk Access?

[Jeff Gold <jgold@mazunetworks.com>]

Helge Hafting wrote:
> With nothing attached, any write to the serial device might go
> through a lengthy timeout because of flow control.  [...] But I can't
> see why it'd make scsi disks slower. The scsi host adapter 
> initialization writes some messages of course, but there should be no
> more console accesses during a hdparm test run.

This makes sense to me.  When I attach a serial cable and use that to 
login (I've got agetty running), hdparm produces no console messages 
that I can see using minicom.  Still, the disk throughput is around 1.5 
MB/sec for some reason.  When I disable the serial console in grub.conf 
and reboot I get over 70 MB/sec again.

A combination of out-of-tree patches (mainly network related but also 
one to disable PM_TIMERS) seem to eliminate the issue even with the 
serial console enabled, at least for the moment.  That means I no longer 
have a problem, but the whole thing is mysterious to me.

                                        Jeff