From: Keir Fraser <keir@xen.org>
To: Olaf Hering <olaf@aepfle.de>, xen-devel@lists.xensource.com
Subject: Re: [PATCH 12/17] xenpaging: handle HVMCOPY_gfn_paged_out in copy_from/to_user
Date: Wed, 15 Dec 2010 11:35:21 +0000 [thread overview]
Message-ID: <C92E5879.2906B%keir@xen.org> (raw)
In-Reply-To: <20101206205912.343173055@aepfle.de>
On 06/12/2010 20:59, "Olaf Hering" <olaf@aepfle.de> wrote:
> mem_event_put_request(d, &req);
> +
> + if ( req.flags & MEM_EVENT_FLAG_VCPU_PAUSED )
> + {
> + wait_event(d->wq, mfn_valid(gfn_to_mfn(p2m, gfn, &p2mt)) &&
> !p2m_is_paging(p2mt));
> + }
> +
This I find interesting. Do you not race the xenpaging daemon satisfying
your page-in request, but then very quickly paging it out again? In which
case you might never wake up!
I think the condition you wait on should be for a response to your paging
request. A wake_up() alone is not really sufficient; you need some kind of
explicit flagging to the vcpu too. Could the paging daemon stick a response
in a shared ring, or otherwise explicitly flag to this vcpu that it's
request has been fully satisfied and it's time to wake up and retry its
operation? Well, really that's a rhetorical question, because that is
exactly what you need to implement for this waitqueue strategy to work
properly!
-- Keir
next prev parent reply other threads:[~2010-12-15 11:35 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-06 20:59 [PATCH 00/17] xenpaging changes for xen-unstable Olaf Hering
2010-12-06 20:59 ` [PATCH 01/17] xenpaging: close xch handle in xenpaging_init error path Olaf Hering
2010-12-14 18:52 ` Ian Jackson
2010-12-06 20:59 ` [PATCH 02/17] xenpaging: remove perror usage " Olaf Hering
2010-12-06 20:59 ` [PATCH 03/17] xenpaging: print DPRINTF ouput if XENPAGING_DEBUG is in environment Olaf Hering
2010-12-06 20:59 ` [PATCH 04/17] xenpaging: print number of evicted pages Olaf Hering
2010-12-06 20:59 ` [PATCH 05/17] xenpaging: remove duplicate xc_interface_close call Olaf Hering
2010-12-06 20:59 ` [PATCH 06/17] xenpaging: do not use DPRINTF/ERROR if xch handle is unavailable Olaf Hering
2010-12-06 20:59 ` [PATCH 07/17] xenpaging: update xch usage Olaf Hering
2010-12-06 20:59 ` [PATCH 08/17] xenpaging: make vcpu_sleep_nosync() optional in mem_event_check_ring() Olaf Hering
2010-12-06 20:59 ` [PATCH 09/17] xenpaging: update machine_to_phys_mapping[] during page deallocation Olaf Hering
2010-12-06 20:59 ` [PATCH 10/17] xenpaging: update machine_to_phys_mapping[] during page-in Olaf Hering
2010-12-14 22:58 ` Olaf Hering
2010-12-15 10:47 ` Tim Deegan
2010-12-06 20:59 ` [PATCH 11/17] xenpaging: drop paged pages in guest_remove_page Olaf Hering
2010-12-06 20:59 ` [PATCH 12/17] xenpaging: handle HVMCOPY_gfn_paged_out in copy_from/to_user Olaf Hering
2010-12-07 9:27 ` Jan Beulich
2010-12-07 9:45 ` Olaf Hering
2010-12-15 11:35 ` Keir Fraser [this message]
2010-12-15 13:51 ` Olaf Hering
2010-12-15 14:08 ` Keir Fraser
2010-12-06 20:59 ` [PATCH 13/17] xenpaging: page only pagetables for debugging Olaf Hering
2010-12-06 20:59 ` [PATCH 14/17] xenpaging: prevent page-out of first 16MB Olaf Hering
2010-12-06 20:59 ` [PATCH 15/17] xenpaging: start xenpaging via config option Olaf Hering
2010-12-06 20:59 ` [PATCH 16/17] xenpaging: add dynamic startup delay for xenpaging Olaf Hering
2010-12-06 20:59 ` [PATCH 17/17] xenpaging: (sparse) documenation Olaf Hering
2010-12-06 21:16 ` [PATCH 00/17] xenpaging changes for xen-unstable Olaf Hering
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