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

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Message-ID: <5506B04D.1070506@lge.com>
Date:	Mon, 16 Mar 2015 19:28:29 +0900
From:	Gioh Kim <gioh.kim@....com>
To:	Roman Pen <r.peniaev@...il.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Nick Piggin <npiggin@...nel.dk>,
	Eric Dumazet <edumazet@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	David Rientjes <rientjes@...gle.com>,
	WANG Chao <chaowang@...hat.com>,
	Fabian Frederick <fabf@...net.be>,
	Christoph Lameter <cl@...ux.com>,
	Rob Jones <rob.jones@...ethink.co.uk>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH 0/3] [RFC] mm/vmalloc: fix possible exhaustion of vmalloc
 space



2015-03-13 ПРШФ 9:12ПЁ Roman Pen РЬ(АЁ) ОД Бл:
> 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@...ux-foundation.org>
> Cc: Nick Piggin <npiggin@...nel.dk>
> Cc: Eric Dumazet <edumazet@...gle.com>
> Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
> Cc: David Rientjes <rientjes@...gle.com>
> Cc: WANG Chao <chaowang@...hat.com>
> Cc: Fabian Frederick <fabf@...net.be>
> Cc: Christoph Lameter <cl@...ux.com>
> Cc: Gioh Kim <gioh.kim@....com>
> Cc: Rob Jones <rob.jones@...ethink.co.uk>
> Cc: linux-mm@...ck.org
> Cc: linux-kernel@...r.kernel.org
> Cc: stable@...r.kernel.org
> 
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