Re: [Xen-devel] Issues with Xenpaging in Xen-4.2.1

[sahilsuneja <sahilsuneja@xxxxxxxxx>]

sahilsuneja wrote
> Hi,
> 
> I know Xenpaging is still at an experimental stage, but I still wanted to
> test it out. Sadly, I could not get it to work reliably.
> 
> I have an AMD RVI enabled linux 3.2 host, and I am using linux 2.6.35-22
> HVM guests. After booting a few guests normally upto the host RAM limit, I
> do the following to enable paging for a few guests:
/
>>/usr/lib/xen/bin/xenpaging -f /var/lib/xen/xenpaging/pagefile-hvm-guest -d
1 &
>>xenstore-write /local/domain/1/memory/target-tot_pages $((1024*512))
/
> 
> (here '1' is the dom_id and pagefile-hvm-guest is the backing paging file
> for the hvm guest)
> 
> I am then able to boot more VMs and I can see the corresponding pagefiles
> increase in size for the xenpaging enabled guests.
> 
> The problem is when I go back to the guests on which I enabled xenpaging,
> I see the following errors when I run any basic commands like vim, top,
> less /proc/meminfo:
/
> xc: error: Error populating page 100: Internal error
> xc: error: Error loading 100 during page-in (22 = Invalid argument):
> Internal error
/
> 
> This happens even when there is paged-out memory from other guests to be
> had, and the system is not out of RAM for paging in guest's memory.
> 
> It seems like a page-in error on gfn 100, but that is strange as, from I
> what I gathered from the xenpaging code, policy_default.c starts paging
> only after half of the guest's gfns : current_gfn = max_pages / 2 (inside
> policy_default.c: policy_init())
> 
> I was expecting there to be other stability issues rather that this kind
> of an error.
> 
> Could someone please help me understand this and let me know if I am doing
> something incorrectly. 
> 
> Also, there do not seem to be any interesting messages in xm dmesg or in
> /var/log/xen*.
> 
> Thanks,
> 
> Sahil Suneja
> Ph.D. Student
> University of Toronto





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