From: Keir Fraser <keir.xen@gmail.com>
To: James Harper <james.harper@bendigoit.com.au>,
xen devel <xen-devel@lists.xensource.com>
Subject: Re: unfair servicing of DomU vbd requests
Date: Thu, 03 Mar 2011 07:29:55 +0000 [thread overview]
Message-ID: <C994F3F3.14124%keir.xen@gmail.com> (raw)
In-Reply-To: <AEC6C66638C05B468B556EA548C1A77D01C55B90@trantor>
On 03/03/2011 02:25, "James Harper" <james.harper@bendigoit.com.au> wrote:
> A user of GPLPV (see thread "blue screen in windows balloon driver") is
> getting a bug check in Windows under extremely high memory usage and
> swapfile thrashing tests across multiple DomU's. Responses to my query
> on the ntdev mailing list say that this would happen if an IO request is
> not completed after 70 seconds during high memory/pagefile pressure,
> which is what is happening.
>
> It appears that Dom0 is not servicing vbd requests from DomU's fairly so
> one or two end up getting stalled while the others are mostly okay. How
> are vbd requests supposed to be serviced? Is there potential for one to
> be overlooked for a long period of time? Is there some settings that
> could be changed to avoid this happening?
Dom0 does round-robin scanning of pending event channels these days, which
helps fairness a fair bit. When a pending event is found, the corresponding
blkfront has a batch of requests pulled down and submitted into Linux's
block subsystem at which point we have no more control over scheduling (it
could generally be configured though -- Linux has an admin mechanism for
that).
-- Keir
> Thanks
>
> James
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel
next prev parent reply other threads:[~2011-03-03 7:29 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-03 2:25 unfair servicing of DomU vbd requests James Harper
2011-03-03 7:29 ` Keir Fraser [this message]
2011-03-03 8:22 ` Ian Campbell
2011-03-03 8:28 ` James Harper
2011-03-03 8:30 ` Keir Fraser
2011-03-03 17:09 ` [GIT/PATCH 0/5] " Ian Campbell
2011-03-03 17:10 ` [PATCH 1/5] xen: events: Process event channels notifications in round-robin order Ian Campbell
2011-03-03 17:10 ` [PATCH 2/5] xen: events: Make last processed event channel a per-cpu variable Ian Campbell
2011-03-09 20:32 ` Konrad Rzeszutek Wilk
2011-03-09 20:40 ` Ian Campbell
2011-03-09 20:47 ` Jeremy Fitzhardinge
2011-03-10 8:30 ` Ian Campbell
2011-03-11 17:46 ` Jeremy Fitzhardinge
2011-03-03 17:10 ` [PATCH 3/5] xen: events: Clean up round-robin evtchn scan Ian Campbell
2011-03-03 17:10 ` [PATCH 4/5] xen: events: Make round-robin scan fairer by snapshotting each l2 word Ian Campbell
2011-03-03 17:10 ` [PATCH 5/5] xen: events: Remove redundant clear of l2i at end of round-robin loop Ian Campbell
2011-03-04 8:40 ` [GIT/PATCH 0/5] Re: unfair servicing of DomU vbd requests John Weekes
2011-03-04 9:15 ` Ian Campbell
2011-03-07 19:33 ` John Weekes
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