Commit f13fc107 authored Dec 27, 2019 by Jesper Dangaard Brouer Committed by David S. Miller Jan 02, 2020

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@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 44768dec

net/core/page_pool.c

+9 −0

Original line number	Diff line number	Diff line
		@@ -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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