Re: [Xen-devel] [PATCH 5/6] xen: RTDS: rearrange members of control structures

[Meng Xu <mengxu@xxxxxxxxxxxxx>]

On Fri, Jun 23, 2017 at 6:55 AM, Dario Faggioli
<dario.faggioli@xxxxxxxxxx> wrote:
>
> Nothing changed in `pahole` output, in terms of holes
> and padding, but some fields have been moved, to put
> related members in same cache line.
>
> Signed-off-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
> ---
> Cc: Meng Xu <mengxu@xxxxxxxxxxxxx>
> Cc: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
> ---
>  xen/common/sched_rt.c |   13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/xen/common/sched_rt.c b/xen/common/sched_rt.c
> index 1b30014..39f6bee 100644
> --- a/xen/common/sched_rt.c
> +++ b/xen/common/sched_rt.c
> @@ -171,11 +171,14 @@ static void repl_timer_handler(void *data);
>  struct rt_private {
>      spinlock_t lock;            /* the global coarse-grained lock */
>      struct list_head sdom;      /* list of availalbe domains, used for dump 
> */
> +
>      struct list_head runq;      /* ordered list of runnable vcpus */
>      struct list_head depletedq; /* unordered list of depleted vcpus */
> +
> +    struct timer *repl_timer;   /* replenishment timer */
>      struct list_head replq;     /* ordered list of vcpus that need 
> replenishment */
> +
>      cpumask_t tickled;          /* cpus been tickled */
> -    struct timer *repl_timer;   /* replenishment timer */
>  };
>
>  /*
> @@ -185,10 +188,6 @@ struct rt_vcpu {
>      struct list_head q_elem;     /* on the runq/depletedq list */
>      struct list_head replq_elem; /* on the replenishment events list */
>
> -    /* Up-pointers */
> -    struct rt_dom *sdom;
> -    struct vcpu *vcpu;
> -
>      /* VCPU parameters, in nanoseconds */
>      s_time_t period;
>      s_time_t budget;
> @@ -198,6 +197,10 @@ struct rt_vcpu {
>      s_time_t last_start;         /* last start time */
>      s_time_t cur_deadline;       /* current deadline for EDF */
>
> +    /* Up-pointers */
> +    struct rt_dom *sdom;
> +    struct vcpu *vcpu;
> +
>      unsigned flags;              /* mark __RTDS_scheduled, etc.. */
>  };
>

Reviewed-by: Meng Xu <mengxu@xxxxxxxxxxxxx>

BTW, Dario, I'm wondering if you used any tool to give hints about how
to arrange the fields in a structure or you just did it manually?

Thanks,

Meng

-----------
Meng Xu
PhD Candidate in Computer and Information Science
University of Pennsylvania
http://www.cis.upenn.edu/~mengxu/

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