Re: [Xen-devel] X86 arch_domain ginormous, sizeof(struct domain) already == PAGE_SIZE

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 29.01.16 at 17:24, <czuzu@xxxxxxxxxxxxxxx> wrote:
> To investigate I compiled the unaltered domain.c & used the pahole tool 
> (part of dwarves package) to obtain the complete layout of the domain 
> structure (& its members).
> What I obtained:
>      * sizeof(struct domain) is already = 4096 bytes (= PAGE_SIZE)
>      * sizeof(struct arch_domain) [x86] = sizeof(domain.arch) = 3328 
> bytes (arch_domain is marked __cacheline_aligned, i.e. aligned to 128 bytes)
>      * sizeof(domain.arch.hvm_domain) = 2224 bytes
>      * sizeof(domain.arch.hvm_domain.pl_time) = 1088 bytes
> 
> => overall, X86 timers-related information occupies the most.
> 
> One could shrink the domain structure by transforming some of its fields 
> to pointers, e.g. I could transform the pl_time field into a pointer and 
> dynamically allocate its data when domain_create is called.

Sounds like a reasonable measure. I wasn't aware we're exactly on
the boundary right now.

Jan


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