On 11/28/12 9:59 AM, Zack Weinberg wrote:
A gnumake flag that obsessive mozconfig tweakers may want to test is
--load-average (-l).
I played with this a bit in the past. My experience was that the load
average reacts much too slowly to new processes, so Make would fire off
a huge batch of compilation processes (hundreds of them!), driving the
computer deeply into swap. Tens of minutes later, that batch would all
finish at the same time and Make would spawn a new batch. Overall
results were disastrously bad.
I wondered if that would happen. At least, builds also involve a _wee_
bit of IO, and so it seemed possible the flag could in a negative
feedback loop... EG, start with 1 process doing mostly IO --> spawn more
because the CPU load is low --> IO saturates, throughput drops --> IO's
hopeless, CPU drops because everything's waiting on drive heads
frantically swinging back and forth --> hey, low load, spawn moar!
I can't imagine -l is useful to
*anyone* with the behavior it currently has. It does what it does
largely because that was the only gauge available back in the days of
System V, I think.
It sounded to me like it was more intended for use on shared build
systems of yore... "I would like to run an astounding 3 parallel tasks,
but be nice when assignments are due and the system load is over 50."
Justin
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