From: Trevor Higgins <plan9fullfrontal@qs.co.nz>
To: 9front@9front.org
Subject: Re: [9front] Bug in time cmd?
Date: Wed, 11 Mar 2020 17:15:02 +1300 [thread overview]
Message-ID: <c7cd60b0-508f-c57d-bfd0-99c138e74d88@qs.co.nz> (raw)
In-Reply-To: <218E628908F4F406572E19D8F6D873AA@eigenstate.org>
On 03/11/2020 03:33 PM, ori@eigenstate.org wrote:
>> On 03/11/2020 01:11 PM, Alex Musolino wrote:
>>
>>> These figures come from the Waitmsg structure returned by wait(2). The
>>> 'u' time is the total user time of the child process *and descendants*.
>>> Given that you likely have a multiprocessor and mk will parallelise its
>>> work according to the NPROC environemnt variable, that ought to explain
>>> how you are able to achieve 14s of user time in only 6s real time.
>> Ok, setting NROC=1 verifies the result I am seeing.
>> While I understand the info, I have to think what this actually means as
>> a measurement.
>> I guess it is telling me that 16 threads only makes a 2x speed
>> improvement. Which seems to correlate
>> with the fact that the load on the CPU never gets very high. Utilization
>> is poor.
>>
> out of curiosity, are you running on a machine with 16 physical cores?
>
Only across two cpus. I only have one cpu running plan9. So it is 8cores
16 threads. How you count cores I stopped trying to figure out long
ago. Even assuming threads added no time saving, then 8 -> 2 is still
poor utilization. Under Linux , core threads make a measurable
difference to performance.
--
We need another plan
next prev parent reply other threads:[~2020-03-11 4:15 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-11 0:11 Alex Musolino
2020-03-11 2:28 ` Trevor Higgins
2020-03-11 2:33 ` ori
2020-03-11 4:15 ` Trevor Higgins [this message]
2020-03-11 4:45 ` ori
-- strict thread matches above, loose matches on Subject: below --
2020-03-10 23:39 Trevor Higgins
2020-03-13 16:55 ` [9front] " Ethan Gardener
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