From mboxrd@z Thu Jan 1 00:00:00 1970 From: neidhard.kim@lge.com (Jongsung Kim) Date: Tue, 13 Oct 2015 11:06:44 +0900 Subject: [PATCH] ARM:mm: fix kmap_atomic_to_page In-Reply-To: <5778996.I0Vmityi0g@wuerfel> References: <1444129773-12632-1-git-send-email-chanho.min@lge.com> <20151007090121.GC21513@n2100.arm.linux.org.uk> <561B457F.5090104@lge.com> <5778996.I0Vmityi0g@wuerfel> Message-ID: <561C6734.7010509@lge.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 10/12/2015 06:27 PM, Arnd Bergmann wrote: > How about changing the zcomp code to pass the page pointer instead of the kernel space pointer? That would avoid having to do the kmap_atomic, which can itself be expensive on 32-bit machines and should not be needed here if you have a HW DMA engine doing the compression. Arnd Mainline zram uses lzo / lz4 library functions as backend. Using kmap_atomic and passing address look reasonable. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752906AbbJMCH4 (ORCPT ); Mon, 12 Oct 2015 22:07:56 -0400 Received: from LGEAMRELO12.lge.com ([156.147.23.52]:41191 "EHLO lgeamrelo12.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752009AbbJMCHz (ORCPT ); Mon, 12 Oct 2015 22:07:55 -0400 X-Original-SENDERIP: 156.147.1.126 X-Original-MAILFROM: neidhard.kim@lge.com X-Original-SENDERIP: 10.178.37.74 X-Original-MAILFROM: neidhard.kim@lge.com Subject: Re: [PATCH] ARM:mm: fix kmap_atomic_to_page To: Arnd Bergmann , linux-arm-kernel@lists.infradead.org References: <1444129773-12632-1-git-send-email-chanho.min@lge.com> <20151007090121.GC21513@n2100.arm.linux.org.uk> <561B457F.5090104@lge.com> <5778996.I0Vmityi0g@wuerfel> Cc: Russell King - ARM Linux , Nicolas Pitre , Gunho Lee , Chanho Min , linux-kernel@vger.kernel.org From: Jongsung Kim Message-ID: <561C6734.7010509@lge.com> Date: Tue, 13 Oct 2015 11:06:44 +0900 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <5778996.I0Vmityi0g@wuerfel> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/12/2015 06:27 PM, Arnd Bergmann wrote: > How about changing the zcomp code to pass the page pointer instead of the kernel space pointer? That would avoid having to do the kmap_atomic, which can itself be expensive on 32-bit machines and should not be needed here if you have a HW DMA engine doing the compression. Arnd Mainline zram uses lzo / lz4 library functions as backend. Using kmap_atomic and passing address look reasonable.