From: Michal Hocko <mhocko@kernel•org>
To: Mahesh J Salgaonkar <mahesh@linux•vnet.ibm.com>
Cc: linuxppc-dev <linuxppc-dev@ozlabs•org>,
Linux Kernel <linux-kernel@vger•kernel.org>,
Hari Bathini <hbathini@linux•vnet.ibm.com>,
Ananth N Mavinakayanahalli <ananth@linux•vnet.ibm.com>,
Srikar Dronamraju <srikar@linux•vnet.ibm.com>,
"Aneesh Kumar K.V" <aneesh.kumar@linux•vnet.ibm.com>,
Anshuman Khandual <khandual@linux•vnet.ibm.com>,
Andrew Morton <akpm@linux-foundation•org>,
Joonsoo Kim <iamjoonsoo.kim@lge•com>,
Ananth Narayan <ananth@in•ibm.com>,
kernelfans@gmail•com
Subject: Re: [RFC PATCH v6 0/4] powerpc/fadump: Improvements and fixes for firmware-assisted dump.
Date: Mon, 16 Jul 2018 10:26:46 +0200 [thread overview]
Message-ID: <20180716082646.GF17280@dhcp22.suse.cz> (raw)
In-Reply-To: <153172096333.29252.4376707071382727345.stgit@jupiter.in.ibm.com>
On Mon 16-07-18 11:32:56, Mahesh J Salgaonkar wrote:
> One of the primary issues with Firmware Assisted Dump (fadump) on Power
> is that it needs a large amount of memory to be reserved. This reserved
> memory is used for saving the contents of old crashed kernel's memory before
> fadump capture kernel uses old kernel's memory area to boot. However, This
> reserved memory area stays unused until system crash and isn't available
> for production kernel to use.
How much memory are we talking about. Regular kernel dump process needs
some reserved memory as well. Why that is not a big problem?
> Instead of setting aside a significant chunk of memory that nobody can use,
> take advantage ZONE_MOVABLE to mark a significant chunk of reserved memory
> as ZONE_MOVABLE, so that the kernel is prevented from using, but
> applications are free to use it.
Why kernel cannot use that memory while userspace can?
[...]
> Documentation/powerpc/firmware-assisted-dump.txt | 18 +++
> arch/powerpc/include/asm/fadump.h | 7 +
> arch/powerpc/kernel/fadump.c | 123 +++++++++++++++++--
> arch/powerpc/platforms/pseries/hotplug-memory.c | 7 +
> include/linux/mmzone.h | 2
> mm/page_alloc.c | 146 ++++++++++++++++++++++
> 6 files changed, 290 insertions(+), 13 deletions(-)
This is quite a large change and you didn't seem to explain why we need
it.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2018-07-16 8:26 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-16 6:02 [RFC PATCH v6 0/4] powerpc/fadump: Improvements and fixes for firmware-assisted dump Mahesh J Salgaonkar
2018-07-16 6:03 ` [RFC PATCH v6 1/4] mm/page_alloc: Introduce an interface to mark reserved memory as ZONE_MOVABLE Mahesh J Salgaonkar
2018-07-16 6:03 ` [RFC PATCH v6 2/4] powerpc/fadump: Reservationless firmware assisted dump Mahesh J Salgaonkar
2018-07-16 6:03 ` [RFC PATCH v6 3/4] powerpc/fadump: throw proper error message on fadump registration failure Mahesh J Salgaonkar
2018-07-16 6:03 ` [RFC PATCH v6 4/4] powerpc/fadump: Do not allow hot-remove memory from fadump reserved area Mahesh J Salgaonkar
2018-07-16 8:26 ` Michal Hocko [this message]
2018-07-17 11:28 ` [RFC PATCH v6 0/4] powerpc/fadump: Improvements and fixes for firmware-assisted dump Mahesh Jagannath Salgaonkar
2018-07-17 11:52 ` Michal Hocko
2018-07-18 16:22 ` Mahesh Jagannath Salgaonkar
2018-07-19 8:08 ` Michal Hocko
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