[PATCH] Re: latancy test of -ac22-riel

["John Fremlin" <vii@penguinpowered.com>]

Roger Larsson <roger.larsson@norran.net> writes:

[...]

> I retried running with normal prio - then I get stalls
> of > 350ms...

I think some stalls are most probably due to try_to_free_pages below

page_alloc.c::__alloc_pages
	/*
	 * Uhhuh. All the zones have been critical, which means that
	 * we'd better do some synchronous swap-out. kswapd has not
	 * been able to cope..
	 */
	if (!(current->flags & PF_MEMALLOC)) {
		if (!try_to_free_pages(gfp_mask)) {
			if (!(gfp_mask & __GFP_HIGH))
				goto fail;
		}
		goto fail;
	}

That is, it happens in times of high memory stress and when I comment
it out the pauses go away but I'm not sure that this is a good
long-term solution ;-) though IMHO the behaviour without it (VM
killing process) is better than the behaviour with it (paging until
power is cycled).

[...]

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