Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:6 as permitted sender) client-ip=2620:137:e000::3:6;
Date:   Tue, 28 Nov 2023 15:34:32 +0800
From:   Baoquan He <bhe@redhat.com>
To:     Shijie Huang <shijie@amperemail.onmicrosoft.com>,
        k-hagio-ab@nec.com
Cc:     Huang Shijie <shijie@os.amperecomputing.com>, lijiang@redhat.com,
        akpm@linux-foundation.org, vgoyal@redhat.com, dyoung@redhat.com,
        kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
        patches@amperecomputing.com
Subject: Re: [PATCH] crash_core: export vmemmap when CONFIG_SPARSEMEM_VMEMMAP
 is enabled
Message-ID: <ZWWYCLb73RYXGcpG@MiWiFi-R3L-srv>
References: <20231127020727.25296-1-shijie@os.amperecomputing.com>
 <ZWQEP4SczFh+GUHq@MiWiFi-R3L-srv>
 <33021b87-4c6a-45fc-a6ae-265765cfcd78@amperemail.onmicrosoft.com>
 <ZWVdxAv/PPHY3Ndl@MiWiFi-R3L-srv>
 <a7d85fee-23cd-4b85-adc6-16980b6e5e02@amperemail.onmicrosoft.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <a7d85fee-23cd-4b85-adc6-16980b6e5e02@amperemail.onmicrosoft.com>
Precedence: bulk

On 11/28/23 at 11:31am, Shijie Huang wrote:
> 
> 在 2023/11/28 11:25, Baoquan He 写道:
> > On 11/27/23 at 11:18am, Shijie Huang wrote:
> > > 在 2023/11/27 10:51, Baoquan He 写道:
> > > > Hi,
> > > > 
> > > > On 11/27/23 at 10:07am, Huang Shijie wrote:
> > > > > In memory_model.h, if CONFIG_SPARSEMEM_VMEMMAP is configed,
> > > > > kernel will use vmemmap to do the __pfn_to_page/page_to_pfn,
> > > > > and kernel will not use the "classic sparse" to do the
> > > > > __pfn_to_page/page_to_pfn.
> > > > > 
> > > > > So export the vmemmap when CONFIG_SPARSEMEM_VMEMMAP is configed.
> > > > > This makes the user applications (crash, etc) get faster
> > > > > pfn_to_page/page_to_pfn operations too.
> > > > Are there Crash or makedupfile patches posted yet to make use of this?
> > > I have patches for Crash to use the 'vmemmap', but after this patch is
> > > merged, I will send it out.
> > > 
> > > (I think Kazu will not merge a crash patch which depends on a kernel patch
> > > which is not merged.)
> > Maybe post these userspace patches too so that Kazu can evaluat if those
> > improvement is necessary?
> 
> No problem.  I will send out them later.

Thank, Shijie. Let's wait and see if Kazu has any comment about these.