On Tue 14-11-17 16:56:49, Josef Bacik wrote:
> From: Josef Bacik <jba...@fb.com>
>
> The flexible proportion stuff has been used to track how many pages we
> are writing out over a period of time, so counts everything in single
> increments. If we wanted to use another base value we need to be able
> to adjust the batch size to fit our the units we'll be using for the
> proportions.
>
> Signed-off-by: Josef Bacik <jba...@fb.com>
Frankly, I had to look into the code to understand what the patch is about.
Can we rephrase the changelog like:
Currently flexible proportion code is using fixed per-cpu counter batch size
since all the counters use only increment / decrement to track number of
pages which completed writeback. When we start tracking amount of done
writeback in different units, we need to update per-cpu counter batch size
accordingly. Make counter batch size configurable on a per-proportion
domain basis to allow for this.
Honza
> ---
> include/linux/flex_proportions.h | 4 +++-
> lib/flex_proportions.c | 11 +++++------
> 2 files changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/flex_proportions.h
> b/include/linux/flex_proportions.h
> index 0d348e011a6e..853f4305d1b2 100644
> --- a/include/linux/flex_proportions.h
> +++ b/include/linux/flex_proportions.h
> @@ -20,7 +20,7 @@
> */
> #define FPROP_FRAC_SHIFT 10
> #define FPROP_FRAC_BASE (1UL << FPROP_FRAC_SHIFT)
> -
> +#define FPROP_BATCH_SIZE (8*(1+ilog2(nr_cpu_ids)))
> /*
> * ---- Global proportion definitions ----
> */
> @@ -31,6 +31,8 @@ struct fprop_global {
> unsigned int period;
> /* Synchronization with period transitions */
> seqcount_t sequence;
> + /* batch size */
> + s32 batch_size;
> };
>
> int fprop_global_init(struct fprop_global *p, gfp_t gfp);
> diff --git a/lib/flex_proportions.c b/lib/flex_proportions.c
> index 2cc1f94e03a1..5552523b663a 100644
> --- a/lib/flex_proportions.c
> +++ b/lib/flex_proportions.c
> @@ -44,6 +44,7 @@ int fprop_global_init(struct fprop_global *p, gfp_t gfp)
> if (err)
> return err;
> seqcount_init(&p->sequence);
> + p->batch_size = FPROP_BATCH_SIZE;
> return 0;
> }
>
> @@ -166,8 +167,6 @@ void fprop_fraction_single(struct fprop_global *p,
> /*
> * ---- PERCPU ----
> */
> -#define PROP_BATCH (8*(1+ilog2(nr_cpu_ids)))
> -
> int fprop_local_init_percpu(struct fprop_local_percpu *pl, gfp_t gfp)
> {
> int err;
> @@ -204,11 +203,11 @@ static void fprop_reflect_period_percpu(struct
> fprop_global *p,
> if (period - pl->period < BITS_PER_LONG) {
> s64 val = percpu_counter_read(&pl->events);
>
> - if (val < (nr_cpu_ids * PROP_BATCH))
> + if (val < (nr_cpu_ids * p->batch_size))
> val = percpu_counter_sum(&pl->events);
>
> percpu_counter_add_batch(&pl->events,
> - -val + (val >> (period-pl->period)), PROP_BATCH);
> + -val + (val >> (period-pl->period)), p->batch_size);
> } else
> percpu_counter_set(&pl->events, 0);
> pl->period = period;
> @@ -219,7 +218,7 @@ static void fprop_reflect_period_percpu(struct
> fprop_global *p,
> void __fprop_inc_percpu(struct fprop_global *p, struct fprop_local_percpu
> *pl)
> {
> fprop_reflect_period_percpu(p, pl);
> - percpu_counter_add_batch(&pl->events, 1, PROP_BATCH);
> + percpu_counter_add_batch(&pl->events, 1, p->batch_size);
> percpu_counter_add(&p->events, 1);
> }
>
> @@ -267,6 +266,6 @@ void __fprop_inc_percpu_max(struct fprop_global *p,
> return;
> } else
> fprop_reflect_period_percpu(p, pl);
> - percpu_counter_add_batch(&pl->events, 1, PROP_BATCH);
> + percpu_counter_add_batch(&pl->events, 1, p->batch_size);
> percpu_counter_add(&p->events, 1);
> }
> --
> 2.7.5
>
--
Jan Kara <j...@suse.com>
SUSE Labs, CR
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