processes not getting fair share of available disk I/O (was:
Re: TCP parameters and interpreting tcpdump output )
freebsd at sopwith.solgatos.com
Thu Nov 23 09:36:36 PST 2006
> > > > hw.ata.wc=3D3D0
> > > ^^^^^^^^^^^
> > > "Make my hard drive go reeeeally slow please (just in case I crash)" :)
> > Slower, yes, but not *that* slow.
> > Normal ls : 0.032 second. Two processes using same disk, multiply by two,
> > so 0.064 second. Maybe the multiplier is more than 2, call it 10x, so
> > 0.32 second. But I'm seeing a factor of over 9100x.
> Humour me and turn it back on, then see what happens.
Where is the knob to turn the write cache on/off on a per-drive basis
in FreeBSD? I can do this in NetBSD, but the only knob I can find in
FreeBSD affects all drives, and requires a reboot.
Humour me and read the Subject line. The ls does not get its fair share
of disk I/O.
Both times are with the disk's write cache in write-through mode.
I'm not comparing times with the write cache in different modes.
I'm comparing ls by itself against ls competing with cp.
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