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Date: Sun, 8 Mar 2009 12:37:21 +0800
Message-ID: <386072610903072037q532de253n5697dca04d155710@mail.gmail.com>
Subject: Re: [GIT PULL] x86, percpu: implement and use reserved percpu alloc
From: Bryan Wu <cooloney@kernel.org>
To: Tejun Heo <tj@kernel.org>
Cc: mingo@elte.hu, rusty@rustcorp.com.au, tglx@linutronix.de, x86@kernel.org,
       linux-kernel@vger.kernel.org, hpa@zytor.com, efault@gmx.de,
       jaswinder@kernel.org
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On Fri, Mar 6, 2009 at 2:46 PM, Tejun Heo <tj@kernel.org> wrote:
>
> Hello,
>
> Please pull from the following git vector.
>
> ?git://git.kernel.org/pub/scm/linux/kernel/git/tj/misc.git tj-percpu
>
> This patchset implements reserved percpu alloc from the first chunk
> and uses it for static perpcu variables in modules on x86_64. ?This is
> necessary because x86_64 expects symbols to be relocatable using 32bit
> relocations but dynamic percpu allocation does not guarantee it
> leading to relocation overflow during module load.
>
> This can happen to any of the x86_64 percpu first chunk allocators but
> the embedding allocator is most likely to trigger it as the first
> chunk is located in the normal kernel memory allocation area while all
> the other chunks will be allocated in the vmalloc area which is very
> far from the first chunk.
>
> This type of reservation will be necessary for other architectures too
> where addressing mode used for percpu acess uses offsets with limited
> range to access symbols (e.g. ia64 w/ the magic 64k percpu page).
>
> This problem was first reported and bisected by Mike Galbraith[2].
>
> This patchset is against the current x86/core/percpu[1] and contains
> the following patches.
>
> ?0001-percpu-clean-up-percpu-constants.patch
> ?0002-percpu-cosmetic-renames-in-pcpu_setup_first_chunk.patch
> ?0003-percpu-improve-first-chunk-initial-area-map-handlin.patch
> ?0004-percpu-use-negative-for-auto-for-pcpu_setup_first_c.patch
> ?0005-x86-make-embedding-percpu-allocator-return-excessiv.patch
> ?0006-percpu-add-an-indirection-ptr-for-chunk-page-map-ac.patch
> ?0007-percpu-module-implement-reserved-allocation-and-us.patch
> ?0008-x86-percpu-setup-reserved-percpu-area-for-x86_64.patch
>
> 0001-0004 makes misc updates to percpu in preparation of later
> changes. ?0005 fixes a case where excessive memory can be set aside in
> the first chunk when using the embedding allocator. ?0006-0008
> implement reserved allocation and use it for x86_64.
>
> Bryan Wu, can you please review #0001? ?It contains small change in
> blackfin. ?It's mostly trivial but just in case.
>

Hi Tejun,

Sorry for the delay, it looks fine for me.

-Bryan

> Diffstat follows.
>
> ?arch/blackfin/include/asm/percpu.h | ? 10 -
> ?arch/x86/kernel/setup_percpu.c ? ? | ? 73 +++++++---
> ?include/linux/percpu.h ? ? ? ? ? ? | ? 60 +++-----
> ?kernel/module.c ? ? ? ? ? ? ? ? ? ?| ? ?2
> ?mm/percpu.c ? ? ? ? ? ? ? ? ? ? ? ?| ?267 ++++++++++++++++++++++++++-----------
> ?5 files changed, 274 insertions(+), 138 deletions(-)
>
> Thanks.
>
> --
> tejun
>
> [1] f254f3909efaf59ca2d0f408de2d044dace60706
> [2] http://thread.gmane.org/gmane.linux.kernel/801799
>
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