Re: [PATCH 2/2] block: Convert BDI proportion calculations to flexible proportions

[Fengguang Wu <fengguang.wu@intel.com>]

On Fri, May 04, 2012 at 12:39:20AM +0200, Jan Kara wrote:
> Convert calculations of proportion of writeback each bdi does to new flexible
> proportion code. That allows us to use aging period of fixed wallclock time
> which gives better proportion estimates given the hugely varying throughput of
> different devices.
> 
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---
>  include/linux/backing-dev.h |    6 ++--
>  mm/backing-dev.c            |    5 +--
>  mm/page-writeback.c         |   80 ++++++++++++++++++++----------------------
>  3 files changed, 43 insertions(+), 48 deletions(-)

> +static void vm_completions_period(struct work_struct *work);
> +/* Work for aging of vm_completions */
> +static DECLARE_DEFERRED_WORK(vm_completions_period_work, vm_completions_period);

> +
> +static void vm_completions_period(struct work_struct *work)
> +{
> +	fprop_new_period(&vm_completions);
> +	schedule_delayed_work(&vm_completions_period_work,
> +			      VM_COMPLETIONS_PERIOD_LEN);
> +}
> +

Is it possible to optimize away the periodic work when there are no
disk writes?

Thanks,
Fengguang

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