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From: ebiederm@xmission.com (Eric W. Biederman)
To: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
Cc: vgoyal@redhat.com, cpw@sgi.com,
	kumagai-atsushi@mxc.nes.nec.co.jp, lisa.mitchell@hp.com,
	heiko.carstens@de.ibm.com, akpm@linux-foundation.org,
	kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
	zhangyanfei@cn.fujitsu.com
Subject: Re: [PATCH v3 18/21] vmcore: check if vmcore objects satify mmap()'s page-size boundary requirement
Date: Tue, 19 Mar 2013 15:38:45 -0700	[thread overview]
Message-ID: <877gl3koay.fsf@xmission.com> (raw)
In-Reply-To: <20130316040228.15064.28019.stgit@localhost6.localdomain6> (HATAYAMA Daisuke's message of "Sat, 16 Mar 2013 13:02:29 +0900")

HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com> writes:

> If there's some vmcore object that doesn't satisfy page-size boundary
> requirement, remap_pfn_range() fails to remap it to user-space.
>
> Objects that posisbly don't satisfy the requirement are ELF note
> segments only. The memory chunks corresponding to PT_LOAD entries are
> guaranteed to satisfy page-size boundary requirement by the copy from
> old memory to buffer in 2nd kernel done in later patch.
>
> This patch doesn't copy each note segment into the 2nd kernel since
> they amount to so large in total if there are multiple CPUs. For
> example, current maximum number of CPUs in x86_64 is 5120, where note
> segments exceed 1MB with NT_PRSTATUS only.

So you require the first kernel to reserve an additional 20MB, instead
of just 1.6MB.  336 bytes versus 4096 bytes.

That seems like completely the wrong tradeoff in memory consumption,
filesize, and backwards compatibility.

Eric

  parent reply	other threads:[~2013-03-19 22:38 UTC|newest]

Thread overview: 76+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-03-16  4:00 [PATCH v3 00/21] kdump, vmcore: support mmap() on /proc/vmcore HATAYAMA Daisuke
2013-03-16  4:00 ` [PATCH v3 01/21] vmcore: reference e_phoff member explicitly to get position of program header table HATAYAMA Daisuke
2013-03-19 21:44   ` Eric W. Biederman
2013-03-21  2:50     ` HATAYAMA Daisuke
2013-03-21  6:11       ` Eric W. Biederman
2013-03-21 14:12       ` Vivek Goyal
2013-03-22  0:25         ` HATAYAMA Daisuke
2013-03-16  4:00 ` [PATCH v3 02/21] vmcore: clean up by removing unnecessary variable HATAYAMA Daisuke
2013-03-16  4:01 ` [PATCH v3 03/21] vmcore: rearrange program headers without assuming consequtive PT_NOTE entries HATAYAMA Daisuke
2013-03-19 21:59   ` Eric W. Biederman
2013-03-16  4:01 ` [PATCH v3 04/21] vmcore, sysfs: export ELF note segment size instead of vmcoreinfo data size HATAYAMA Daisuke
2013-03-16  4:01 ` [PATCH v3 05/21] vmcore: allocate buffer for ELF headers on page-size alignment HATAYAMA Daisuke
2013-03-16  4:01 ` [PATCH v3 06/21] vmcore: round up buffer size of ELF headers by PAGE_SIZE HATAYAMA Daisuke
2013-03-19 22:07   ` Eric W. Biederman
2013-03-16  4:01 ` [PATCH v3 07/21] vmcore, procfs: introduce a flag to distinguish objects copied in 2nd kernel HATAYAMA Daisuke
2013-03-19 19:35   ` Andrew Morton
2013-03-16  4:01 ` [PATCH v3 08/21] vmcore: copy non page-size aligned head and tail pages " HATAYAMA Daisuke
2013-03-19 19:37   ` Andrew Morton
2013-03-19 20:59   ` Eric W. Biederman
2013-03-19 21:22     ` Vivek Goyal
2013-03-19 23:35       ` Eric W. Biederman
2013-03-16  4:01 ` [PATCH v3 09/21] vmcore: modify vmcore clean-up function to free buffer on " HATAYAMA Daisuke
2013-03-16  4:01 ` [PATCH v3 10/21] vmcore: clean up read_vmcore() HATAYAMA Daisuke
2013-03-16  4:01 ` [PATCH v3 11/21] vmcore: read buffers for vmcore objects copied from old memory HATAYAMA Daisuke
2013-03-16  4:01 ` [PATCH v3 12/21] vmcore: allocate per-cpu crash_notes objects on page-size boundary HATAYAMA Daisuke
2013-03-19 21:06   ` Eric W. Biederman
2013-03-19 22:12   ` Eric W. Biederman
2013-03-20 13:48     ` Vivek Goyal
2013-03-20 20:48       ` Eric W. Biederman
2013-03-16  4:02 ` [PATCH v3 13/21] kexec: allocate vmcoreinfo note buffer " HATAYAMA Daisuke
2013-03-19 21:07   ` Eric W. Biederman
2013-03-19 22:12   ` Eric W. Biederman
2013-03-16  4:02 ` [PATCH v3 14/21] kexec, elf: introduce NT_VMCORE_DEBUGINFO note type HATAYAMA Daisuke
2013-03-16  4:02 ` [PATCH v3 15/21] elf: introduce NT_VMCORE_PAD type HATAYAMA Daisuke
2013-03-16  4:02 ` [PATCH v3 16/21] kexec: fill note buffers by NT_VMCORE_PAD notes in page-size boundary HATAYAMA Daisuke
2013-03-19 22:17   ` Eric W. Biederman
2013-03-16  4:02 ` [PATCH v3 17/21] vmcore: check NT_VMCORE_PAD as a mark indicating the end of ELF note buffer HATAYAMA Daisuke
2013-03-19 21:11   ` Eric W. Biederman
2013-03-21  2:59     ` HATAYAMA Daisuke
2013-03-21  3:54       ` Eric W. Biederman
2013-03-21 14:36         ` Vivek Goyal
2013-03-22  0:30           ` HATAYAMA Daisuke
2013-03-22  0:41             ` Eric W. Biederman
2013-03-19 22:20   ` Eric W. Biederman
2013-03-16  4:02 ` [PATCH v3 18/21] vmcore: check if vmcore objects satify mmap()'s page-size boundary requirement HATAYAMA Daisuke
2013-03-19 20:02   ` Andrew Morton
2013-03-19 21:22     ` Eric W. Biederman
2013-03-20 13:51     ` Vivek Goyal
2013-03-19 22:38   ` Eric W. Biederman [this message]
2013-03-20 13:57     ` Vivek Goyal
2013-03-20 20:55       ` Eric W. Biederman
2013-03-21  3:25         ` HATAYAMA Daisuke
2013-03-21  4:18           ` Eric W. Biederman
2013-03-21  6:14             ` HATAYAMA Daisuke
2013-03-21  6:29               ` Eric W. Biederman
2013-03-21  6:46                 ` HATAYAMA Daisuke
2013-03-21  7:07                   ` Eric W. Biederman
2013-03-21 15:21                     ` Vivek Goyal
2013-03-21 15:27                       ` Vivek Goyal
2013-03-22  0:43                         ` HATAYAMA Daisuke
2013-03-22  0:54                         ` Eric W. Biederman
2013-03-22  2:30                           ` HATAYAMA Daisuke
2013-03-21 14:57                 ` Vivek Goyal
2013-03-21  7:22               ` Eric W. Biederman
2013-03-21 14:49                 ` Vivek Goyal
2013-03-22  7:11                   ` HATAYAMA Daisuke
2013-03-21 13:50         ` Vivek Goyal
2013-03-16  4:02 ` [PATCH v3 19/21] vmcore: round-up offset of vmcore object in page-size boundary HATAYAMA Daisuke
2013-03-16  4:02 ` [PATCH v3 20/21] vmcore: count holes generated by round-up operation for vmcore size HATAYAMA Daisuke
2013-03-16  4:02 ` [PATCH v3 21/21] vmcore: introduce mmap_vmcore() HATAYAMA Daisuke
2013-03-19 19:30 ` [PATCH v3 00/21] kdump, vmcore: support mmap() on /proc/vmcore Andrew Morton
2013-03-21  3:52   ` HATAYAMA Daisuke
2013-03-21  6:16     ` Eric W. Biederman
2013-03-21  6:35       ` HATAYAMA Daisuke
2013-03-21  7:14         ` Eric W. Biederman
2013-03-19 23:16 ` Eric W. Biederman

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