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Thu, 17 Apr 2025 09:12:21 -0700 (PDT) From: "Uladzislau Rezki (Sony)" To: Andrew Morton Cc: linux-mm@kvack.org, LKML , Baoquan He , Christoph Hellwig , Uladzislau Rezki , Oleksiy Avramchenko , Mateusz Guzik Subject: [PATCH 4/4] vmalloc: Align nr_vmalloc_pages and vmap_lazy_nr Date: Thu, 17 Apr 2025 18:12:16 +0200 Message-Id: <20250417161216.88318-4-urezki@gmail.com> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250417161216.88318-1-urezki@gmail.com> References: <20250417161216.88318-1-urezki@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Currently both atomics share one cache-line: ... ffffffff83eab400 b vmap_lazy_nr ffffffff83eab408 b nr_vmalloc_pages ... those are global variables and they are only 8 bytes apart. Since they are modified by different threads this causes a false sharing. This can lead to a performance drop due to unnecessary cache invalidations. After this patch it is aligned to a cache line boundary: ... ffffffff8260a600 d vmap_lazy_nr ffffffff8260a640 d nr_vmalloc_pages ... Cc: Mateusz Guzik Signed-off-by: Uladzislau Rezki (Sony) --- mm/vmalloc.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 77da4613f07ff..54f60d62051da 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -1008,7 +1008,8 @@ static BLOCKING_NOTIFIER_HEAD(vmap_notify_list); static void drain_vmap_area_work(struct work_struct *work); static DECLARE_WORK(drain_vmap_work, drain_vmap_area_work); -static atomic_long_t nr_vmalloc_pages; +static __cacheline_aligned_in_smp atomic_long_t nr_vmalloc_pages; +static __cacheline_aligned_in_smp atomic_long_t vmap_lazy_nr; unsigned long vmalloc_nr_pages(void) { @@ -2117,8 +2118,6 @@ static unsigned long lazy_max_pages(void) return log * (32UL * 1024 * 1024 / PAGE_SIZE); } -static atomic_long_t vmap_lazy_nr = ATOMIC_LONG_INIT(0); - /* * Serialize vmap purging. There is no actual critical section protected * by this lock, but we want to avoid concurrent calls for performance -- 2.39.5