From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AE0862F6165; Sun, 21 Dec 2025 11:55:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766318127; cv=none; b=GUUl2beQhvp84YzV3UQbHJQyXa9FatJw/gDn+tHYriKOUWHBxAgHdvhFXFJ93OCYYOweHnBFR8XWCSKQ1IP5XJ16ohLfAQ0Dhig5q0gip52qZt1ZurN9lR1zaa8Xix3RSzxEgTz1myTeZlYCXVlg4cXhTDiU4tDNm1Ob7Dk98T4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766318127; c=relaxed/simple; bh=cl0Pp9gIMy9qgGyo+31RVCvJ8tyH3yPUScmFvHzlmzo=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=RjCFmqri88625zKijVbzmzm0tbb7CE34rB7o2XRbxpxVtPdzC5Uuny42NvMdtYClHL4ACtigigGcnmYCacma0uvLrUl6tROWU9cMmp7o8W8GIXxeiYE6y6JZR4hKFnIRhG1Tn+T5oQZIJTgG6lgI7mf72djUhTLg/CJMf8NqQI4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=m4PYcanK; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="m4PYcanK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B4BB9C4CEFB; Sun, 21 Dec 2025 11:55:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1766318127; bh=cl0Pp9gIMy9qgGyo+31RVCvJ8tyH3yPUScmFvHzlmzo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=m4PYcanKwIXIAkG+coVrKkljBDifB1QabUlFnQ3ypVg0NVtQmBnB/6oN9x7PYRhIN 0sVLieQfV0c237oif8izgVL1JTccjIUrFLcqvp/rJkxoXihijgtCOoqM2wpqE+j1aA 4QHvF2jDFuv9hzwc824cIqpLcrP9LDmLWgBb4GY6bvymBDeY4DW131179tHLfTOKVe CnyfUFUdje3+Tr0xR7jKzeHBVsptHeHCmcyUdYOSig3bJ8LweSk0ZGUOrmPz1VWPP6 y6PzTrm9GUKr2OhwTd9GLn0uRJbfLf0pr2+a/MwsAOClEIQwARj/A89uJ0ZJMJbyVC rO7K1fA0KE4hg== Date: Sun, 21 Dec 2025 13:55:23 +0200 From: Leon Romanovsky To: Barry Song <21cnbao@gmail.com> Cc: catalin.marinas@arm.com, m.szyprowski@samsung.com, robin.murphy@arm.com, will@kernel.org, ada.coupriediaz@arm.com, anshuman.khandual@arm.com, ardb@kernel.org, iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, maz@kernel.org, ryan.roberts@arm.com, surenb@google.com, v-songbaohua@oppo.com, zhengtangquan@oppo.com Subject: Re: [PATCH 5/6] dma-mapping: Allow batched DMA sync operations if supported by the arch Message-ID: <20251221115523.GI13030@unreal> References: <20251219053658.84978-1-21cnbao@gmail.com> <20251219053658.84978-6-21cnbao@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20251219053658.84978-6-21cnbao@gmail.com> On Fri, Dec 19, 2025 at 01:36:57PM +0800, Barry Song wrote: > From: Barry Song > > This enables dma_direct_sync_sg_for_device, dma_direct_sync_sg_for_cpu, > dma_direct_map_sg, and dma_direct_unmap_sg to use batched DMA sync > operations when possible. This significantly improves performance on > devices without hardware cache coherence. > > Tangquan's initial results show that batched synchronization can reduce > dma_map_sg() time by 64.61% and dma_unmap_sg() time by 66.60% on an MTK > phone platform (MediaTek Dimensity 9500). The tests were performed by > pinning the task to CPU7 and fixing the CPU frequency at 2.6 GHz, > running dma_map_sg() and dma_unmap_sg() on 10 MB buffers (10 MB / 4 KB > sg entries per buffer) for 200 iterations and then averaging the > results. > > Cc: Catalin Marinas > Cc: Will Deacon > Cc: Marek Szyprowski > Cc: Robin Murphy > Cc: Ada Couprie Diaz > Cc: Ard Biesheuvel > Cc: Marc Zyngier > Cc: Anshuman Khandual > Cc: Ryan Roberts > Cc: Suren Baghdasaryan > Cc: Tangquan Zheng > Signed-off-by: Barry Song > --- > kernel/dma/direct.c | 28 ++++++++++----- > kernel/dma/direct.h | 86 +++++++++++++++++++++++++++++++++++++++------ > 2 files changed, 95 insertions(+), 19 deletions(-) <...> > if (!dev_is_dma_coherent(dev)) > - arch_sync_dma_for_device(paddr, sg->length, > - dir); > + arch_sync_dma_for_device_batch_add(paddr, sg->length, dir); <...> > -static inline dma_addr_t dma_direct_map_phys(struct device *dev, > +#ifdef CONFIG_ARCH_WANT_BATCHED_DMA_SYNC > +static inline void dma_direct_sync_single_for_cpu_batch_add(struct device *dev, > + dma_addr_t addr, size_t size, enum dma_data_direction dir) > +{ > + phys_addr_t paddr = dma_to_phys(dev, addr); > + > + if (!dev_is_dma_coherent(dev)) > + arch_sync_dma_for_cpu_batch_add(paddr, size, dir); > + > + __dma_direct_sync_single_for_cpu(dev, paddr, size, dir); > +} > +#endif > + > +static inline void dma_direct_sync_single_for_cpu(struct device *dev, > + dma_addr_t addr, size_t size, enum dma_data_direction dir) > +{ > + phys_addr_t paddr = dma_to_phys(dev, addr); > + > + if (!dev_is_dma_coherent(dev)) > + arch_sync_dma_for_cpu(paddr, size, dir); > + > + __dma_direct_sync_single_for_cpu(dev, paddr, size, dir); > +} > + I'm wondering why you don't implement this batch‑sync support inside the arch_sync_dma_*() functions. Doing so would minimize changes to the generic kernel/dma/* code and reduce the amount of #ifdef‑based spaghetti. Thanks."