[H-GEN] Clock Time Loss When Copying Files

Bruce Campbell bc at humbug.org.au
Tue Jun 6 22:27:08 EDT 2000


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On Wed, 7 Jun 2000, Frank Brand wrote:

fbrand> On Wed, 07 Jun 2000, you wrote:
fbrand> > On Wed, 7 Jun 2000, Frank Brand wrote:
fbrand> > I wonder if the machine is masking out timer interrupts while doing IO,
fbrand> > and so losing time.  (Is it a slow machine or hard drive?)  In that case
fbrand> > it would be interesting to see what the hardware real-time-clock says
fbrand> > compared to the system clock.  If it is accurate, then you can use it to
fbrand> > reset the system clock at regular intervals, or you could run NTP.
fbrand> 
fbrand> No I would not describe it as slow AMD K6 2 500, 128 Mb RAM
fbrand> 
fbrand> I suspect that the file transfer by network may make it a
fbrand> bit slow if it has to share the network link with other
fbrand> machines. I suspect that you are correct in that it
fbrand> suspends reference to the clock while a long I/O process
fbrand> occurs.

Not quite correct.  There are two things occuring in the above.  One,
reading/writing data from/to an IDE HDD (mucho interrupts).  Two,
transferring data out to the network card.  As you mentioned that it is a
BNC (ie, Coax) network, a valid assumption would be older network cards
(again, mucho interrupts required)

If the network itself is busy, further interrupts may be generated (on
both machines) due to retransmits caused by collisions.  Other machines on
the network alone would not cause a slowdown.

This is why decent servers have SCSI drives, and operate on switched
networks ;)

-- 
  Bruce.                                                         | VP/BOFH
  Infinite Monkeys.  Infinite Keyboards.  I see no Shakespeare.  |  HUMBUG
  Usenet may or may not be an implementation of RFC2795.         |     PAN


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