linux-kernel - Re: [PATCH v2] mm/vmap: Add a notifier for when we run out of vmap address space

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Date:	Thu, 17 Mar 2016 13:41:56 +0000
From:	Chris Wilson <chris@...is-wilson.co.uk>
To:	intel-gfx@...ts.freedesktop.org
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	Roman Peniaev <r.peniaev@...il.com>,
	Mel Gorman <mgorman@...hsingularity.net>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm/vmap: Add a notifier for when we run out of vmap
 address space

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@...is-wilson.co.uk>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: David Rientjes <rientjes@...gle.com>
> Cc: Roman Peniaev <r.peniaev@...il.com>
> Cc: Mel Gorman <mgorman@...hsingularity.net>
> Cc: linux-mm@...ck.org
> Cc: linux-kernel@...r.kernel.org
> ---
>  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
>  #endif
>  
> +struct notitifer_block;
Omg. /o\
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre