Re: [PATCH 0/3] [RFC] mm/vmalloc: fix possible exhaustion of vmalloc space

[Gioh Kim <gioh.kim@lge.com>]

2015-03-13 ?AEA 9:12?! Roman Pen AI(?!)  3/4 ' +-U:
> Hello all.
> 
> Recently I came across high fragmentation of vm_map_ram allocator: vmap_block
> has free space, but still new blocks continue to appear.  Further investigation
> showed that certain mapping/unmapping sequence can exhaust vmalloc space.  On
> small 32bit systems that's not a big problem, cause purging will be called soon
> on a first allocation failure (alloc_vmap_area), but on 64bit machines, e.g.
> x86_64 has 45 bits of vmalloc space, that can be a disaster.

I think the problem you comments is already known so that I wrote comments about it as
"it could consume lots of address space through fragmentation".

Could you tell me about your situation and reason why it should be avoided?


> 
> Fixing this I also did some tweaks in allocation logic of a new vmap block and
> replaced dirty bitmap with min/max dirty range values to make the logic simpler.
> 
> I would like to receive comments on the following three patches.
> 
> Thanks.
> 
> Roman Pen (3):
>    mm/vmalloc: fix possible exhaustion of vmalloc space caused by
>      vm_map_ram allocator
>    mm/vmalloc: occupy newly allocated vmap block just after allocation
>    mm/vmalloc: get rid of dirty bitmap inside vmap_block structure
> 
>   mm/vmalloc.c | 94 ++++++++++++++++++++++++++++++++++--------------------------
>   1 file changed, 54 insertions(+), 40 deletions(-)
> 
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Nick Piggin <npiggin@kernel.dk>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> Cc: David Rientjes <rientjes@google.com>
> Cc: WANG Chao <chaowang@redhat.com>
> Cc: Fabian Frederick <fabf@skynet.be>
> Cc: Christoph Lameter <cl@linux.com>
> Cc: Gioh Kim <gioh.kim@lge.com>
> Cc: Rob Jones <rob.jones@codethink.co.uk>
> Cc: linux-mm@kvack.org
> Cc: linux-kernel@vger.kernel.org
> Cc: stable@vger.kernel.org
> 

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