out_of_memory called to often

[Jason Li]

Hi,

We are running an embedded linux (2.4.19) with no swap
sapce. And we haven't applied any rmap yet.

Currely when the system runs low (reached the
pages_low water-mark), kswapd kicks in. But soon after
kswapd kicks in, the out_of_memory is called due to
swapd not being able to reclaim enough pages from the
page cache from each run of it. I don't understand why
sometimes swapd can't reclaim the SWAP_CLUSTER_MAX
number of pages.

We know there are still some number of cache pages
that can be reclaimed if we run the following c
program:

int main() {
 int i, j;
 char *tmp[10000]

 for (i=0; i<NUMBER_OF_PAGES_LEFT_BEFORE_pages_low;
i++) tmp[i]=malloc(4k);
 for (i=0; i<NUMBER_OF_PAGES_LEFT_BEFORE_pages_low;
i++) free(tmp[i]);
}
To solve this problem, I am trying to make a
conditional call to the out_of_memory() -- only if the
pages_min is reached, then the out_of_memory() can be
called.

If we can solve the swapd livelock problem, is this a
feasible solution? If you have a better idea, can you
please share with us?

Any input will be greatly appreciated.

Thanks very much in advance! Please include my email
address in your reply.

-Jason

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