From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f72.google.com (mail-pa0-f72.google.com [209.85.220.72]) by kanga.kvack.org (Postfix) with ESMTP id 034D86B0038 for ; Wed, 9 Nov 2016 04:10:41 -0500 (EST) Received: by mail-pa0-f72.google.com with SMTP id bi5so48810336pad.0 for ; Wed, 09 Nov 2016 01:10:40 -0800 (PST) Received: from mailout3.samsung.com (mailout3.samsung.com. [203.254.224.33]) by mx.google.com with ESMTPS id n9si34302592pad.79.2016.11.09.01.10.40 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 09 Nov 2016 01:10:40 -0800 (PST) Received: from epcpsbgm1new.samsung.com (epcpsbgm1 [203.254.230.26]) by mailout3.samsung.com (Oracle Communications Messaging Server 7.0.5.31.0 64bit (built May 5 2014)) with ESMTP id <0OGD00A7UATQM2A0@mailout3.samsung.com> for linux-mm@kvack.org; Wed, 09 Nov 2016 18:10:38 +0900 (KST) From: Jaewon Kim Subject: [PATCH] [RFC] drivers: dma-coherent: use MEMREMAP_WB instead of MEMREMAP_WC Date: Wed, 09 Nov 2016 18:10:09 +0900 Message-id: <1478682609-26477-1-git-send-email-jaewon31.kim@samsung.com> Sender: owner-linux-mm@kvack.org List-ID: To: brian.starkey@arm.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, jaewon31.kim@samsung.com Commit 6b03ae0d42bf (drivers: dma-coherent: use MEMREMAP_WC for DMA_MEMORY_MA) added MEMREMAP_WC for DMA_MEMORY_MAP. If, however, CPU cache can be used on DMA_MEMORY_MAP, I think MEMREMAP_WC can be changed to MEMREMAP_WB. On my local ARM device, memset in dma_alloc_from_coherent sometimes takes much longer with MEMREMAP_WC compared to MEMREMAP_WB. Test results on AArch64 by allocating 4MB with putting trace_printk right before and after memset. MEMREMAP_WC : 11.0ms, 5.7ms, 4.2ms, 4.9ms, 5.4ms, 4.3ms, 3.5ms MEMREMAP_WB : 0.7ms, 0.6ms, 0.6ms, 0.6ms, 0.6ms, 0.5ms, 0.4 ms Signed-off-by: Jaewon Kim --- drivers/base/dma-coherent.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c index 640a7e6..0512a1d 100644 --- a/drivers/base/dma-coherent.c +++ b/drivers/base/dma-coherent.c @@ -33,7 +33,7 @@ static bool dma_init_coherent_memory( goto out; if (flags & DMA_MEMORY_MAP) - mem_base = memremap(phys_addr, size, MEMREMAP_WC); + mem_base = memremap(phys_addr, size, MEMREMAP_WB); else mem_base = ioremap(phys_addr, size); if (!mem_base) -- 1.9.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org