From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38140 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1726114AbgDPUhl (ORCPT ); Thu, 16 Apr 2020 16:37:41 -0400 Date: Thu, 16 Apr 2020 13:37:36 -0700 From: Minchan Kim Subject: Re: [PATCH 10/28] mm: only allow page table mappings for built-in zsmalloc Message-ID: <20200416203736.GB50092@google.com> References: <20200408115926.1467567-1-hch@lst.de> <20200408115926.1467567-11-hch@lst.de> <20200409160826.GC247701@google.com> <20200409165030.GG20713@hirez.programming.kicks-ass.net> <20200409170813.GD247701@google.com> <20200410023845.GA2354@jagdpanzerIV.localdomain> <20200410231136.GA101325@google.com> <20200411072052.GA31242@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200411072052.GA31242@lst.de> Sender: linux-s390-owner@vger.kernel.org List-ID: To: Christoph Hellwig Cc: Sergey Senozhatsky , Peter Zijlstra , Andrew Morton , "K. Y. Srinivasan" , Haiyang Zhang , Stephen Hemminger , Wei Liu , x86@kernel.org, David Airlie , Daniel Vetter , Laura Abbott , Sumit Semwal , Sakari Ailus , Nitin Gupta , Robin Murphy , Christophe Leroy , linuxppc-dev@lists.ozlabs.org, linux-hyperv@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org, linux-arm-kernel@lists.infradead.org, linux-s390@vger.kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org Hi Christoph, Sorry for the late. On Sat, Apr 11, 2020 at 09:20:52AM +0200, Christoph Hellwig wrote: > Hi Minchan, > > On Fri, Apr 10, 2020 at 04:11:36PM -0700, Minchan Kim wrote: > > It doesn't mean we couldn't use zsmalloc as module any longer. It means > > we couldn't use zsmalloc as module with pgtable mapping whcih was little > > bit faster on microbenchmark in some architecutre(However, I usually temped > > to remove it since it had several problems). However, we could still use > > zsmalloc as module as copy way instead of pgtable mapping. Thus, if someone > > really want to rollback the feature, they should provide reasonable reason > > why it doesn't work for them. "A little fast" wouldn't be enough to exports > > deep internal to the module. > > do you have any data how much faster it is on arm (and does that include > arm64 as well)? Besides the exports which were my prime concern, https://github.com/sjenning/zsmapbench I need to recall the memory. IIRC, it was almost 30% faster at that time in ARM so was not trivial at that time. However, it was story from several years ago. > zsmalloc with pgtable mappings also is the only user of map_kernel_range > outside of vmalloc.c, if it really is another code base for tiny > improvements we could mark map_kernel_range or in fact remove it entirely > and open code it in the remaining callers. I alsh have temped to remove it. Let me have time to revist it in this chance. Thanks.