Re: [GIT PULL] x86, percpu: implement and use reserved percpu alloc

Ingo Molnar
2009-03-06T08:06:59Z

* 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.
>
> 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(-)

Pulled, thanks Tejun!

Ingo