linux-kernel - Re: [PATCH 08/27] mm, vmscan: Simplify the logic deciding whether kswapd sleeps

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Date:	Wed, 22 Jun 2016 17:30:41 +0200
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Mel Gorman <mgorman@...hsingularity.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux-MM <linux-mm@...ck.org>
Cc:	Rik van Riel <riel@...riel.com>,
	Johannes Weiner <hannes@...xchg.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 08/27] mm, vmscan: Simplify the logic deciding whether
 kswapd sleeps

On 06/21/2016 04:15 PM, Mel Gorman wrote:
> kswapd goes through some complex steps trying to figure out if it
> should stay awake based on the classzone_idx and the requested order.
> It is unnecessarily complex and passes in an invalid classzone_idx to
> balance_pgdat().  What matters most of all is whether a larger order has
> been requsted and whether kswapd successfully reclaimed at the previous
> order. This patch irons out the logic to check just that and the end result
> is less headache inducing.
>
> Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>
> Acked-by: Johannes Weiner <hannes@...xchg.org>

Acked-by: Vlastimil Babka <vbabka@...e.cz>

I'm just not entirely convinced that the direct full sleep bypass is worth the 
added complexity. I can even imagine it being counter productive in some 
situations. But it's not a big issue.