Messages in this thread | | | From | Andrey Melnikoff <> | Subject | Re: Serial Console and Slow SCSI Disk Access? | Date | Thu, 22 Jun 2006 20:18:54 +0400 |
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David Lang <dlang@digitalinsight.com> wrote: > On Tue, 20 Jun 2006, Helge Hafting wrote:
> > Jeff Gold wrote: > >> 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. > > I can see one possibility, that I didn't think of yesterday. > > Do the scsi host adapter share its interrupt with the serial line? > > (Boot a kernel that has the problem, and when scsi is slow, do a > > cat /proc/interrupts > > If the scsi and the serial driver share an interrupt, then that is the source > > of the problem.
[skipp]
> I ran into a similar problem (extremely slow scsi performance), but hadn't > reported it as I made a lot of changes at the same time (moved from 2.6.7 to > 2.6.12.3 as well as enabling the serial console). but with this report I wanted > to chime in with a weak 'me-too'. I haven't rebooted without the serial console > yet to confirm this, but I will do so shortly, and try 2.6.17 to see if it has a > similar problem or not.
2.6.17.1 here, MB Intel SCB20, aic7899 onboard. aic7xxx compilled in, serial core compilled in, serial console enabled. With/without serial sonsole - speed 66.0 Mb/s.
Maybe problem related to MB chipset?
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