Re: Exaggerated swap usage && -aa lockup

Javier Marcet
2002-11-30T13:54:44Z

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* Rik van Riel <riel@conectiva.com.br> [021130 02:57]:

>> root # vmstat 1
>> procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
>> r b swpd free buff cache si so bi bo in cs us sy id wa
>> 0 1 265048 5248 32248 119108 6 15 65 62 252 585 21 6 73 0
>> 1 6 266648 4480 32316 120300 0 4656 2152 4652 1348 821 13 8 79 0
>> 1 0 265052 4496 31036 120184 8 336 1668 340 1226 765 15 7 78 0
>> 0 1 265052 4496 31112 121564 4 0 3152 0 1198 894 18 8 74 0
>> 1 0 265052 4504 31076 123112 0 0 3024 8576 1229 857 17 7 76 0
> ^^^^^^^^^^^^^^^^^^^

>Looks like my guess was right after all. The amount of swap
>IO is maybe 10% of the amount of filesystem IO in your vmstat
>snippet above.

[...]

>Two things could be happening here:

>1) the kernel decides to cache the wrong things in the
> page cache

>and/or

>2) the IO scheduler is giving worse latencies now

>If the problem is (1) it might get resolved by using the -rmap
>or -aa kernels. If the problem is (2) you'll want Andrew Morton's
>read_latency patch (which I'll port to 2.4.20 real soon now).

I tend to believe is (1). I was using 2.4.20-jam0 (-aa derived) all this
morning. It seemed to behave better than 2.4.20-rc4-ac1 on this point. I
compiled a couple apps without problems, had different apps and servers
running while both si & so and bi & bo were low. However, when I was
uncompressing mozilla-1.2.tar.gz the system locked up, just as
2.4.20-rc2aa1 did days before. ALT-SYSRQ allowed me to reboot, but I did
not take note of any kernel dump...

I am now running 2.5.47-ac6 and things are _way_ better in any aspect.
I'll post some vmstat output later when the system has been running for
a while. So far it has already uncompressed mozilla's source with no
slowdown or lockup.

--
Javier Marcet <jmarcet@pobox.com>

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