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Message-ID: <20140721130629.GA15122@amd.pavel.ucw.cz> Date: Mon, 21 Jul 2014 15:06:29 +0200 From: Pavel Machek <pavel@....cz> To: Joerg Roedel <joro@...tes.org> Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>, Len Brown <len.brown@...el.com>, linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH 0/6 v2] PM / Hibernate: Memory bitmap scalability improvements Hi! > > > The last patch adds touching the soft lockup watchdog in > > > rtree_next_node. This is necessary because the worst case > > > performance (all bits set in the forbidden_pages_map and > > > free_pages_map) is the same as with the old implementation > > > and may still cause soft lockups. Patch 6 avoids this. > > > > Ok, so what about simpler patch? Just touch the watchdog? > > That would just cover the problem that the bitmap data structure and the > algorithm in swsusp_free do not scale well on bigmem machines. And is it a problem? Hibernation of 12TB machine will take 6 hours if you back your swap with SSDs. Does not scale == burns additional 60 seconds of CPU time. I think we can live with that... ...because noone sane will hibernate 12TB machine. > > Additional 70 seconds will be lost in noise if you write 12TB of RAM > > to (even quite fast) disk. > > Sure, but you would still get the soft lockup warnings when swsusp_free > runs in the end. Yes, that's why I propose to apply just patch 6 -- to avoid soft lockup warnings. Best regards, Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- 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/
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