linux-kernel - Re: [2.6.35-rc3] select useful number of entries for DMA debugging...

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20100710154331.GF10080@8bytes.org>
Date:	Sat, 10 Jul 2010 17:43:31 +0200
From:	Joerg Roedel <joro@...tes.org>
To:	Daniel J Blueman <daniel.blueman@...il.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [2.6.35-rc3] select useful number of entries for DMA
	debugging...

On Sat, Jul 10, 2010 at 03:52:04PM +0100, Daniel J Blueman wrote:
> On 9 July 2010 22:33, Linus Torvalds <torvalds@...ux-foundation.org> wrote:
> > On Mon, Jul 5, 2010 at 1:35 AM, Daniel J Blueman
> > <daniel.blueman@...il.com> wrote:
> >> When booting 2.6.35-rc3 on some different x86 boxes with DMA debugging
> >> enabled, I've consistently seen it exhaust the allocated entries during
> >> boot, giving 'DMA-API: debugging out of memory - disabling'.
> >>
> >> Increase number of entries to allow DMA debugging again.
> >
> > Rather than increase the default that gets allocated whenever anybody
> > enables the DMA debugging, I'd really prefer to see people use the
> > kernel command line option if they run out. After all, it's a (pretty
> > esoteric) debug option, and the number of required entries depends on
> > machine configuration. I'd rather not make the default cover a huge
> > number, when you could just add
> >
> >   dma_debug_entries=65536
> >
> > on the kernel boot command line instead for machines that want/need it..
> 
> That said, I am seeing the DMA pool exhaust on a single socket Core i5
> system with Intel graphics and no other adapters - seems like a fairly
> common case. If eg 25% of developers will be using similar to this,
> maybe it's good to make DMA debugging less immediately esoteric?
> 
> On the other hand, I would immediately agree if the exhaustion
> occurred on an atypical setup.

How much memory do you have in this machine? We could probably make the
number of pre-allocated entries dependent on the memory available in the
machine like Ingo suggested some time ago to avoid such problems.

	Joerg

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/