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SubjectRe: dead mem walking ;-)


On Thu, 12 Jul 2001, Dirk Wetter wrote:

>
>
> Hi guys,
>
> On Thu, 12 Jul 2001, Mike Galbraith wrote:
>
> > > > Have you had a chance to try 2.4.7-pre-latest yet? I'd be interested
> > > > in a small sample of vmstat 1 leading into heavy swap with >=pre5 if
> > > > it is still a problem.
> > >
> > > i will definetely check it out and give a report, since the test i did
> > > yesterday the *command* "vmstat 1" in typed in appeared to be :)) more
> > > like "vmstat 180", no kidding.
> >
> > Ok, you have some 'io bound' issues that need to be looked at. Present
> > the data in that light please.
>
> so here is result of my testing: the scenario: vanilla kernel
> 2.4.6, config is CONFIG_HIGHMEM4G=y, it's a dual intel box with 4GB
> mem. the machine was freshly booted before the test with profile=2
> (more detailed data is av. @ www.desy.de/~dirkw/linux-kernel/ )
>
>
>
> a while before the jobs were submitted i did "readprofile | sort -nr | head -10":
> 296497 total 0.3442
> 295348 default_idle 5679.7692
> 300 __rdtsc_delay 10.7143
> 215 si_swapinfo 1.2500
> 138 do_softirq 1.0147
> 107 printk 0.2816
> 28 do_wp_page 0.0272
> 17 schedule 0.0117
> 10 tcp_get_info 0.0077
> 10 filemap_nopage 0.0073
>
> the same after i was able to kill the jobs (see below):
>
> 836552 total 0.9710
> 458757 default_idle 8822.2500
> 361961 __get_swap_page 665.3695
> 6629 si_swapinfo 38.5407
> 1655 do_anonymous_page 5.3734
> 760 file_read_actor 3.0645
> 652 statm_pgd_range 1.6633
> 592 do_softirq 4.3529
> 498 skb_copy_bits 0.5845
> 302 __rdtsc_delay 10.7857


Ok, I've seen that before. __get_swap_page() is horribly innefficient.

The system is _not_ swaping out data, though. Its just aging the
pte's and allocating swap.

And that is what is eating the system performance.

<snip>

Can you please show us the output of /proc/meminfo when the system is
behaving badly ?

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