On Fri, 20 Apr 2007 17:51:58 +0200 Peter Zijlstra <[EMAIL PROTECTED]> wrote:
> Add percpu_counter_mod64() to allow large modifications.
>
> Signed-off-by: Peter Zijlstra <[EMAIL PROTECTED]>
> ---
> include/linux/percpu_counter.h | 9 +++++++++
> lib/percpu_counter.c | 28 ++++++++++++++++++++++++++++
> 2 files changed, 37 insertions(+)
>
> Index: linux-2.6/include/linux/percpu_counter.h
> ===================================================================
> --- linux-2.6.orig/include/linux/percpu_counter.h 2007-04-12
> 13:54:55.000000000 +0200
> +++ linux-2.6/include/linux/percpu_counter.h 2007-04-12 14:00:21.000000000
> +0200
> @@ -36,6 +36,7 @@ static inline void percpu_counter_destro
> }
>
> void percpu_counter_mod(struct percpu_counter *fbc, s32 amount);
> +void percpu_counter_mod64(struct percpu_counter *fbc, s64 amount);
> s64 percpu_counter_sum(struct percpu_counter *fbc);
>
> static inline s64 percpu_counter_read(struct percpu_counter *fbc)
> @@ -81,6 +82,14 @@ percpu_counter_mod(struct percpu_counter
> preempt_enable();
> }
>
> +static inline void
> +percpu_counter_mod64(struct percpu_counter *fbc, s64 amount)
> +{
> + preempt_disable();
> + fbc->count += amount;
> + preempt_enable();
> +}
> +
> static inline s64 percpu_counter_read(struct percpu_counter *fbc)
> {
> return fbc->count;
> Index: linux-2.6/lib/percpu_counter.c
> ===================================================================
> --- linux-2.6.orig/lib/percpu_counter.c 2006-07-31 13:07:38.000000000
> +0200
> +++ linux-2.6/lib/percpu_counter.c 2007-04-12 14:17:12.000000000 +0200
> @@ -25,6 +25,34 @@ void percpu_counter_mod(struct percpu_co
> }
> EXPORT_SYMBOL(percpu_counter_mod);
>
> +void percpu_counter_mod64(struct percpu_counter *fbc, s64 amount)
> +{
> + long count;
> + s32 *pcount;
> + int cpu;
> +
> + if (amount >= FBC_BATCH || amount <= -FBC_BATCH) {
> + spin_lock(&fbc->lock);
> + fbc->count += amount;
> + spin_unlock(&fbc->lock);
> + return;
> + }
This is wrong, a little.
If the counter was at -FBC_BATCH/2 and the caller passed in FBC_BATCH, we
could just set the cpu-local counter to FBC_BATCH/2 instead of going for
the lock.
Probably doesn't matter though.
> + cpu = get_cpu();
> + pcount = per_cpu_ptr(fbc->counters, cpu);
> + count = *pcount + amount;
> + if (count >= FBC_BATCH || count <= -FBC_BATCH) {
> + spin_lock(&fbc->lock);
> + fbc->count += count;
> + *pcount = 0;
> + spin_unlock(&fbc->lock);
> + } else {
> + *pcount = count;
> + }
> + put_cpu();
> +}
> +EXPORT_SYMBOL(percpu_counter_mod64);
Bloaty. Surely we won't be needing this on 32-bit kernels? Even monster
PAE has only 64,000,000 pages and won't be using deltas of more than 4
gigapages?
<Does even 64-bit need to handle 4 gigapages in a single hit? /me suspects
another changelog bug>
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