[PATCH 03/14]: libxenlight, 8MB slack for PV domains

[PATCH 03/14]: libxenlight, 8MB slack for PV domains

[Andres Lagar-Cavilla]

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Contemplate 8MB of slack for PV domains, since they
do ballooning (or flipping network rx) and need
some extra room in their pfn space.

Signed-off-by: Andres Lagar-Cavilla <andres@lagarcavilla.com>


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# HG changeset patch
# User Andres Lagar-Cavilla <andres@lagarcavilla.com>
# Date 1259252810 18000
# Node ID 5b7eed595f810af6a78aa17f28bfbdc0e5d11413
# Parent  eba3584b89d66e702fe9c193c0391b379b9248a0
Contemplate 8MB of slack for PV domains, since they
do ballooning (or flipping network rx) and need 
some extra room in their pfn space.

Signed-off-by: Andres Lagar-Cavilla <andres@lagarcavilla.com>

diff -r eba3584b89d6 -r 5b7eed595f81 libxl_dom.c
--- a/libxl_dom.c
+++ b/libxl_dom.c
@@ -53,7 +53,8 @@ int build_pre(struct libxl_ctx *ctx, uin
         xc_set_hvm_param(ctx->xch, domid, HVM_PARAM_VPT_ALIGN, (unsigned long) info->vpt_align);
     xc_domain_max_vcpus(ctx->xch, domid, info->max_vcpus);
     xc_domain_setmaxmem(ctx->xch, domid, info->max_memkb + info->video_memkb);
-    xc_domain_set_memmap_limit(ctx->xch, domid, info->max_memkb);
+    xc_domain_set_memmap_limit(ctx->xch, domid, 
+            (info->hvm) ? info->max_memkb : (info->max_memkb + (8*1024)));
 
     if (info->hvm) {
         unsigned long shadow;

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Re: [PATCH 03/14]: libxenlight, 8MB slack for PV domains

[Vincent Hanquez]

On Mon, Nov 30, 2009 at 07:10:58PM +0000, Andres Lagar-Cavilla wrote:
> Contemplate 8MB of slack for PV domains, since they
> do ballooning (or flipping network rx) and need
> some extra room in their pfn space.
> 
> Signed-off-by: Andres Lagar-Cavilla <andres@lagarcavilla.com>

this probably should be in the build structure. not magically adding 8 mb without the
toolstack knowing, otherwise no toolstack can provide more or less slacks on a
per domain basis. And it make precise memory handling a nightmare, and thus
dynamic memory handling too. in some way this parameter is just like the
shadow_memory one in the hvm build structure.

-- 
Vincent

Re: [PATCH 03/14]: libxenlight, 8MB slack for PV domains

[Andres Lagar-Cavilla]

The 8mb slack is not real memory allocated. It's extra room in the pfn 
space. The memory's domain allocation remains capped at the amount 
intended. I haven't seen anyone in xen-devel for five years needing more 
slack than that ') Particularly since the network rx flipping path 
stopped being the default
Andres
Vincent Hanquez wrote:
> On Mon, Nov 30, 2009 at 07:10:58PM +0000, Andres Lagar-Cavilla wrote:
>   
>> Contemplate 8MB of slack for PV domains, since they
>> do ballooning (or flipping network rx) and need
>> some extra room in their pfn space.
>>
>> Signed-off-by: Andres Lagar-Cavilla <andres@lagarcavilla.com>
>>     
>
> this probably should be in the build structure. not magically adding 8 mb without the
> toolstack knowing, otherwise no toolstack can provide more or less slacks on a
> per domain basis. And it make precise memory handling a nightmare, and thus
> dynamic memory handling too. in some way this parameter is just like the
> shadow_memory one in the hvm build structure.
>
>