Re: [PATCH v2] mm/vmap: Add a notifier for when we run out of vmap address space
From: Chris Wilson
Date: Thu Mar 17 2016 - 09:42:10 EST
On Thu, Mar 17, 2016 at 01:34:59PM +0000, Chris Wilson wrote:
> vmaps are temporary kernel mappings that may be of long duration.
> Reusing a vmap on an object is preferrable for a driver as the cost of
> setting up the vmap can otherwise dominate the operation on the object.
> However, the vmap address space is rather limited on 32bit systems and
> so we add a notification for vmap pressure in order for the driver to
> release any cached vmappings.
> The interface is styled after the oom-notifier where the callees are
> passed a pointer to an unsigned long counter for them to indicate if they
> have freed any space.
> v2: Guard the blocking notifier call with gfpflags_allow_blocking()
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: David Rientjes <rientjes@xxxxxxxxxx>
> Cc: Roman Peniaev <r.peniaev@xxxxxxxxx>
> Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
> Cc: linux-mm@xxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> include/linux/vmalloc.h | 4 ++++
> mm/vmalloc.c | 27 +++++++++++++++++++++++++++
> 2 files changed, 31 insertions(+)
> diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
> index d1f1d338af20..edd676b8e112 100644
> --- a/include/linux/vmalloc.h
> +++ b/include/linux/vmalloc.h
> @@ -187,4 +187,8 @@ pcpu_free_vm_areas(struct vm_struct **vms, int nr_vms)
> #define VMALLOC_TOTAL 0UL
> +struct notitifer_block;
Chris Wilson, Intel Open Source Technology Centre