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Message-ID: <20190215224412.16881.89296.stgit@localhost.localdomain> Date: Fri, 15 Feb 2019 14:44:12 -0800 From: Alexander Duyck <alexander.duyck@...il.com> To: netdev@...r.kernel.org, davem@...emloft.net Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, jannh@...gle.com Subject: [net PATCH 1/2] mm: Use fixed constant in page_frag_alloc instead of size + 1 From: Alexander Duyck <alexander.h.duyck@...ux.intel.com> This patch replaces the size + 1 value introduced with the recent fix for 1 byte allocs with a constant value. The idea here is to reduce code overhead as the previous logic would have to read size into a register, then increment it, and write it back to whatever field was being used. By using a constant we can avoid those memory reads and arithmetic operations in favor of just encoding the maximum value into the operation itself. Fixes: 2c2ade81741c ("mm: page_alloc: fix ref bias in page_frag_alloc() for 1-byte allocs") Signed-off-by: Alexander Duyck <alexander.h.duyck@...ux.intel.com> --- mm/page_alloc.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index ebb35e4d0d90..37ed14ad0b59 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -4857,11 +4857,11 @@ void *page_frag_alloc(struct page_frag_cache *nc, /* Even if we own the page, we do not use atomic_set(). * This would break get_page_unless_zero() users. */ - page_ref_add(page, size); + page_ref_add(page, PAGE_FRAG_CACHE_MAX_SIZE); /* reset page count bias and offset to start of new frag */ nc->pfmemalloc = page_is_pfmemalloc(page); - nc->pagecnt_bias = size + 1; + nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1; nc->offset = size; } @@ -4877,10 +4877,10 @@ void *page_frag_alloc(struct page_frag_cache *nc, size = nc->size; #endif /* OK, page count is 0, we can safely set it */ - set_page_count(page, size + 1); + set_page_count(page, PAGE_FRAG_CACHE_MAX_SIZE + 1); /* reset page count bias and offset to start of new frag */ - nc->pagecnt_bias = size + 1; + nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1; offset = size - fragsz; }
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