| To: | Li Yaqiong <liyaq04@xxxxxxxxxx> |
|---|---|
| Subject: | Re: [Xen-devel] About shadow flag(PG_refcounts) |
| From: | Tim Deegan <Tim.Deegan@xxxxxxxxxx> |
| Date: | 2009年1月12日 09:51:54 +0000 |
| Cc: | xen-devel@xxxxxxxxxxxxxxxxxxx |
| Delivery-date: | 2009年1月12日 01:52:27 -0800 |
| Envelope-to: | www-data@xxxxxxxxxxxxxxxxxxx |
| In-reply-to: | <E15C0579851F417EA9A7E0BD17CBD05B@xxxxxxxxxxxxx> |
| List-help: | <mailto:xen-devel-request@lists.xensource.com?subject=help> |
| List-id: | Xen developer discussion <xen-devel.lists.xensource.com> |
| List-post: | <mailto:xen-devel@lists.xensource.com> |
| List-subscribe: | <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe> |
| List-unsubscribe: | <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe> |
| References: | <E15C0579851F417EA9A7E0BD17CBD05B@xxxxxxxxxxxxx> |
| Sender: | xen-devel-bounces@xxxxxxxxxxxxxxxxxxx |
| User-agent: | Mutt/1.5.17 (2007年11月01日) |
Hi, At 11:15 +0800 on 12 Jan (1231758914), Li Yaqiong wrote: > Hi > In Xen source code, a flag called PG_refcounts is used. Its > explanation is "Refcounts based on shadow tables instead of guest > tables". I can't understand it. Who can explain this flags in detail? If this flag is zero, the shadow pagetables do not do reference counting of the pages that they map (because the normal PV pagetable operations will have done it already when the guest registered its pagetables). If the flag is one, the shadow pagetables _do_ reference-count every mapping they make of a guest page (for example in HVM guests, where there's no other reference counting of the guest's use of memory). Cheers, Tim. -- Tim Deegan <Tim.Deegan@xxxxxxxxxx> Principal Software Engineer, Citrix Systems (R&D) Ltd. [Company #02300071, SL9 0DZ, UK.] _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
| <Prev in Thread] | Current Thread | [Next in Thread> |
|---|---|---|
| ||
| Previous by Date: | Re: [Xen-devel] Two shadow page tables for HVM , Tim Deegan |
|---|---|
| Next by Date: | Re: [Xen-devel] Clocksources and other mysteries , Keir Fraser |
| Previous by Thread: | [Xen-devel] About shadow flag(PG_refcounts) , Li Yaqiong |
| Next by Thread: | [Xen-devel] Clocksources and other mysteries , Carsten Schiers |
| Indexes: | [Date] [Thread] [Top] [All Lists] |