Messages in this thread | | | Date | Wed, 11 Jul 2001 01:04:07 -0500 | From | Dirk Wetter <> | Subject | Re: dead mem pages |
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Rik,
thx for your answer. :)
Rik van Riel wrote:
>On Tue, 10 Jul 2001, Dirk Wetter wrote: > >>>It would be good to know what these 2.8GB of cached pages are. >>> >>believe me, i would like to know too where all the $$$ memory >>went to. ;-) >> > >Most likely swap cache, that means it is the memory from your >simulations, just removed from the page tables and put in the >swap cache. > but why was the machine actually swapping then? sar definetely showed swap and disk activity as the applications started.
>>>Again on a general note, the 2.4 kernel's VM is new and hence not fully >>>mature. So the short and unhelpful answer to your query is probably that >>>the current VM system is not well tuned for your workload (4.3GB of memory >>>hungry simulations on a 4GB machine). >>> >>concerning the maturity that's also the answer i got from the kernel >>guru's at last USENIX in boston. but ihmo it *should* become soon >>better for the future if Linux intends to become bigger in the server >>business. (my $0.02) >> > >It'll get better as soon as we have the time, for 2.4.7 >the VM statistics have already improved a bit so people >are no longer fooled by large "cached" figures ;) > Rik (and Wayne): it's *not only* the statistics. they were swapping like crazy. the only thing the machines were responding immediately to were icmp packets. no tcp/udp. keystrokes on the console were echoed 2 minutes after i typed the command in. with some patience i managed to execute "top" i caught pictures were kswapd was in the first line having 99% or so of one CPU and the load was between 20 and 30.
> >Actual improvements to the code, if needed at all, will >come with time ... more than $0.02 will get you ;) > not that i don't appreciate very much your work, but i had to learn that improvements are needed: we could swap our 4GB machines to death just by submitting jobs in the size of the ~physical memory to them. but i don't have any doubts that you guys will manage to do neccessary changes:-)
i do the profile tests Marcelo suggested (thx) and come back with some numbers.
tschuess :-)
~dirkw
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