Messages in this thread | | | Date | Sun, 06 Aug 2000 19:19:40 -0500 | From | "Jeffrey E. Hundstad" <> | Subject | Re: Can't get a block out edgewise |
| |
Thanks for your response. Actually the dd command is only a simplified version of the real problem. It appears that any big I/O operation slugs the system. The original problem was big SMB file writes over a 100MB/s link.
I have since found a tuning that seems to keep the system going fairly well. I'm using:
echo "40 100 512 512 2000 3000 5000 1884 2" > /proc/sys/vm/bdflush
-- jeffrey hundstad
Ricky Beam wrote:
> On Thu, 3 Aug 2000, Jeffrey E. Hundstad wrote: > ... > >I open two sessions. In one I say "find /", in the other I say "dd > >if=/dev/zero of=big.file bs=10240K count=3". > > Umm, "block size == 10MEG"?!?! Well, right there is half your problem. > It's going to take some time to 10M zeroed buffer and then handing 10M > in one shot to the driver... the system freezes during the 10M read() > of /dev/zero. It becomes very unresponsive during buffer flushing as > a side effect of the way SCSI command queuing works. (Once the driver > command queue is full, no more commands will be sent to the driver until > the queue is empty. I _HATE_ that -- esp. with a DPT I2O controller that > takes _210_ commands and can take _5 MINUTES_ to execute all of them.) > > >Is there any way to smooth out the performance a bit? I'd like some > >writes to occur then some reads so file I/O doesn't grind to a halt. > > change the bs=## to something smaller. The largest block size the SCSI > layer will handle is 64k (it can theoretically go much higher, but doesn't) > > --Ricky
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/
| |