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Date: Fri, 27 Dec 2019 18:13:24 +0100 From: Jesper Dangaard Brouer <brouer@...hat.com> To: netdev@...r.kernel.org Cc: Jesper Dangaard Brouer <brouer@...hat.com>, lirongqing@...du.com, linyunsheng@...wei.com, Ilias Apalodimas <ilias.apalodimas@...aro.org>, Saeed Mahameed <saeedm@...lanox.com>, mhocko@...nel.org, peterz@...radead.org, linux-kernel@...r.kernel.org Subject: [net-next v6 PATCH 2/2] page_pool: help compiler remove code in case CONFIG_NUMA=n When kernel is compiled without NUMA support, then page_pool NUMA config setting (pool->p.nid) doesn't make any practical sense. The compiler cannot see that it can remove the code paths. This patch avoids reading pool->p.nid setting in case of !CONFIG_NUMA, in allocation and numa check code, which helps compiler to see the optimisation potential. It leaves update code intact to keep API the same. $ ./scripts/bloat-o-meter net/core/page_pool.o-numa-enabled \ net/core/page_pool.o-numa-disabled add/remove: 0/0 grow/shrink: 0/3 up/down: 0/-113 (-113) Function old new delta page_pool_create 401 398 -3 __page_pool_alloc_pages_slow 439 426 -13 page_pool_refill_alloc_cache 425 328 -97 Total: Before=3611, After=3498, chg -3.13% Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com> --- net/core/page_pool.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/net/core/page_pool.c b/net/core/page_pool.c index 748f0d36f4be..28fe694f9ab2 100644 --- a/net/core/page_pool.c +++ b/net/core/page_pool.c @@ -113,7 +113,12 @@ static struct page *page_pool_refill_alloc_cache(struct page_pool *pool, /* Softirq guarantee CPU and thus NUMA node is stable. This, * assumes CPU refilling driver RX-ring will also run RX-NAPI. */ +#ifdef CONFIG_NUMA pref_nid = (pool->p.nid == NUMA_NO_NODE) ? numa_mem_id() : pool->p.nid; +#else + /* Ignore pool->p.nid setting if !CONFIG_NUMA, helps compiler */ + pref_nid = numa_mem_id(); /* will be zero like page_to_nid() */ +#endif /* Slower-path: Get pages from locked ring queue */ spin_lock(&r->consumer_lock); @@ -200,7 +205,11 @@ static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool, */ /* Cache was empty, do real allocation */ +#ifdef CONFIG_NUMA page = alloc_pages_node(pool->p.nid, gfp, pool->p.order); +#else + page = alloc_pages(gfp, pool->p.order); +#endif if (!page) return NULL;
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