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Message-ID: <Zc4W8iNOgqI8xrCT@lore-desk>
Date: Thu, 15 Feb 2024 14:51:46 +0100
From: Lorenzo Bianconi <lorenzo@...nel.org>
To: Alexander Lobakin <aleksander.lobakin@...el.com>
Cc: netdev@...r.kernel.org, lorenzo.bianconi@...hat.com, kuba@...nel.org,
davem@...emloft.net, edumazet@...gle.com, pabeni@...hat.com,
hawk@...nel.org, ilias.apalodimas@...aro.org,
linyunsheng@...wei.com, toke@...hat.com
Subject: Re: [RFC net-next] net: page_pool: fix recycle stats for percpu
page_pool allocator
> From: Lorenzo Bianconi <lorenzo@...nel.org>
> Date: Wed, 14 Feb 2024 19:08:40 +0100
>
> > Use global page_pool_recycle_stats percpu counter for percpu page_pool
> > allocator.
> >
> > Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> > ---
> > net/core/page_pool.c | 18 +++++++++++++-----
> > 1 file changed, 13 insertions(+), 5 deletions(-)
> >
> > diff --git a/net/core/page_pool.c b/net/core/page_pool.c
> > index 6e0753e6a95b..1bb83b6e7a61 100644
> > --- a/net/core/page_pool.c
> > +++ b/net/core/page_pool.c
> > @@ -31,6 +31,8 @@
> > #define BIAS_MAX (LONG_MAX >> 1)
> >
> > #ifdef CONFIG_PAGE_POOL_STATS
> > +static DEFINE_PER_CPU(struct page_pool_recycle_stats, pp_recycle_stats);
> > +
> > /* alloc_stat_inc is intended to be used in softirq context */
> > #define alloc_stat_inc(pool, __stat) (pool->alloc_stats.__stat++)
> > /* recycle_stat_inc is safe to use when preemption is possible. */
> > @@ -220,14 +222,19 @@ static int page_pool_init(struct page_pool *pool,
> > pool->has_init_callback = !!pool->slow.init_callback;
> >
> > #ifdef CONFIG_PAGE_POOL_STATS
> > - pool->recycle_stats = alloc_percpu(struct page_pool_recycle_stats);
> > - if (!pool->recycle_stats)
> > - return -ENOMEM;
> > + if (cpuid < 0) {
>
> TBH I don't like the idea of assuming that only system page_pools might
> be created with cpuid >= 0.
> For example, if I have an Rx queue always pinned to one CPU, I might
> want to create a PP for this queue with the cpuid set already to save
> some cycles when recycling. We might also reuse cpuid later for some
> more optimizations or features.
>
> Maybe add a new PP_FLAG indicating that system percpu PP stats should be
> used?
Ack, I like the idea. What about creating a flag to indicate this is a percpu
page_pool instead of relying on cpuid value? Maybe it can be useful in the
future, what do you think?
Regards,
Lorenzo
>
> > + pool->recycle_stats = alloc_percpu(struct page_pool_recycle_stats);
> > + if (!pool->recycle_stats)
> > + return -ENOMEM;
> > + } else {
> > + pool->recycle_stats = &pp_recycle_stats;
> > + }
> > #endif
> >
> > if (ptr_ring_init(&pool->ring, ring_qsize, GFP_KERNEL) < 0) {
> > #ifdef CONFIG_PAGE_POOL_STATS
> > - free_percpu(pool->recycle_stats);
> > + if (cpuid < 0)
> > + free_percpu(pool->recycle_stats);
> > #endif
> > return -ENOMEM;
> > }
> > @@ -251,7 +258,8 @@ static void page_pool_uninit(struct page_pool *pool)
> > put_device(pool->p.dev);
> >
> > #ifdef CONFIG_PAGE_POOL_STATS
> > - free_percpu(pool->recycle_stats);
> > + if (pool->cpuid < 0)
> > + free_percpu(pool->recycle_stats);
> > #endif
> > }
> >
>
> Thanks,
> Olek
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