From: Anders Blomdell <anders.blomdell@domain.hid>
To: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
Cc: xenomai@xenomai.org,
"Daniel Jacques (Alten)" <jacques.daniel@domain.hid>
Subject: Re: [Xenomai-help] rt_heap and DMA32 zone
Date: Tue, 19 Oct 2010 12:52:48 +0200 [thread overview]
Message-ID: <4CBD7880.1020701@domain.hid> (raw)
In-Reply-To: <4CBD7182.2050500@domain.hid>
On 2010-10-19 12.22, Gilles Chanteperdrix wrote:
> Daniel Jacques (Alten) wrote:
>> Hi,
>>
>> I noticed some allocation failure using kmalloc in case of GFP_DMA32 with big size, even if I modified the CONFIG_FORCE_MAX_ZONEORDER to be coherent with my max size (32MB).
>> I don't know the reason of this failure. I am interesting by any idea about this point ...
>> Meanwhile, to avoid this trouble I performed the following additional patch in ksrc/nucleus/heap.c to force using of __get_free_pages instead of kmalloc in case of GFP_DMA32 flag.
>> Jacques
>
> At this point, the problem seems to be in linux code. So, there should
> be no need to modify xenomai code. Are you sure that kmalloc does not
> fail due to fragmentation?
I have some vague recollection that dmaable allocations larger than 2MB should
be done by pci_alloc_consistent and similar (see Documentation/DMA-mapping.txt
or Documentation/DMA-API-HOWTO.txt in newer kernels)
/Anders
--
Anders Blomdell Email: anders.blomdell@domain.hid
Department of Automatic Control
Lund University Phone: +46 46 222 4625
P.O. Box 118 Fax: +46 46 138118
SE-221 00 Lund, Sweden
prev parent reply other threads:[~2010-10-19 10:52 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <DF9F3A3C150B0646A17FF1487C1B6D5E0380C00C@rennsmail06.eu.thmulti.com>
2010-10-13 7:58 ` [Xenomai-help] rt_heap and DMA32 zone Daniel Jacques (Alten)
2010-10-13 9:36 ` Gilles Chanteperdrix
2010-10-13 10:07 ` Daniel Jacques (Alten)
2010-10-13 12:36 ` Gilles Chanteperdrix
2010-10-13 13:51 ` Daniel Jacques (Alten)
2010-10-13 14:07 ` Gilles Chanteperdrix
2010-10-13 14:18 ` Gilles Chanteperdrix
2010-10-13 14:31 ` Daniel Jacques (Alten)
2010-10-14 22:29 ` Gilles Chanteperdrix
2010-10-19 9:37 ` Daniel Jacques (Alten)
2010-10-19 10:22 ` Gilles Chanteperdrix
2010-10-19 10:52 ` Anders Blomdell [this message]
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