From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from g1t0026.austin.hp.com ([15.216.28.33]) by merlin.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1UExvt-0005MZ-Bt for kexec@lists.infradead.org; Mon, 11 Mar 2013 08:18:10 +0000 Message-ID: <513D9338.20402@hp.com> Date: Mon, 11 Mar 2013 16:18:00 +0800 From: Jingbai Ma MIME-Version: 1.0 Subject: Re: [RFC PATCH 0/5] crash dump bitmap: scan memory pages in kernel to speedup kernel dump process References: <20130307145808.29098.41592.stgit@k.asiapacific.hpqcorp.net> <20130307152108.GC2790@redhat.com> <87k3piri3e.fsf@xmission.com> <20130308155216.GB8219@redhat.com> In-Reply-To: <20130308155216.GB8219@redhat.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Vivek Goyal Cc: kexec@lists.infradead.org, linux-kernel@vger.kernel.org, mingo@redhat.com, kumagai-atsushi@mxc.nes.nec.co.jp, "Eric W. Biederman" , hpa@zytor.com, yinghai@kernel.org, Jingbai Ma On 03/08/2013 11:52 PM, Vivek Goyal wrote: > On Thu, Mar 07, 2013 at 01:54:45PM -0800, Eric W. Biederman wrote: >> Vivek Goyal writes: >> >>> On Thu, Mar 07, 2013 at 10:58:18PM +0800, Jingbai Ma wrote: >>>> This patch intend to speedup the memory pages scanning process in >>>> selective dump mode. >>>> >>>> Test result (On HP ProLiant DL980 G7 with 1TB RAM, makedumpfile >>>> v1.5.3): >>>> >>>> Total scan Time >>>> Original kernel >>>> + makedumpfile v1.5.3 cyclic mode 1958.05 seconds >>>> Original kernel >>>> + makedumpfile v1.5.3 non-cyclic mode 1151.50 seconds >>>> Patched kernel >>>> + patched makedumpfile v1.5.3 17.50 seconds >>>> >>>> Traditionally, to reduce the size of dump file, dumper scans all memory >>>> pages to exclude the unnecessary memory pages after capture kernel >>>> booted, and scan it in userspace code (makedumpfile). >>> >>> I think this is not a good idea. It has several issues. >> >> Actually it does not appear to be doing any work in the first kernel. > > Looks like patch3 in series is doing that. > > machine_crash_shutdown(&fixed_regs); > + generate_crash_dump_bitmap(); > machine_kexec(kexec_crash_image); > > So this bitmap seems to be being set just before transitioning into > second kernel. > > I am sure you would not like this extra code in this path. :-) I was thought this function code is pretty simple, could be called here safely. If it's not proper for here, how about before the function machine_crash_shutdown(&fixed_regs)? Furthermore, could you explain the real risks to execute more codes here? Thanks! > > Thanks > Vivek -- Jingbai Ma (jingbai.ma@hp.com) _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec