linux-kernel - Re: [RFC PATCH 1/2] vmscan don't isolate too many pages

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 07 Jul 2009 14:59:29 -0400
From:	Rik van Riel <riel@...hat.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
CC:	LKML <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Minchan Kim <minchan.kim@...il.com>
Subject: Re: [RFC PATCH 1/2] vmscan don't isolate too many pages

KOSAKI Motohiro wrote:

> FAQ
> -------
> Q: Why do you compared zone accumulate pages, not individual zone pages?
> A: If we check individual zone, #-of-reclaimer is restricted by smallest zone.
>    it mean decreasing the performance of the system having small dma zone.

That is a clever solution!  I was playing around a bit with
doing it on a per-zone basis.  Your idea is much nicer.

However, I can see one potential problem with your patch:

+		nr_inactive += zone_page_state(zone, NR_INACTIVE_ANON);
+		nr_inactive += zone_page_state(zone, NR_INACTIVE_FILE);
+		nr_isolated += zone_page_state(zone, NR_ISOLATED_ANON);
+		nr_isolated += zone_page_state(zone, NR_ISOLATED_FILE);
+	}
+
+	return nr_isolated > nr_inactive;

What if we ran out of swap space, or are not scanning the
anon list at all for some reason?

It is possible that there are no inactive_file pages left,
with all file pages already isolated, and your function
still letting reclaimers through.

This means you could still get a spurious OOM.

I guess I should mail out my (ugly) approach, so we can
compare the two :)
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/