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Re: [Xen-devel] [PATCH] xen: increase static dmesg buffer to 64K

To: Keir Fraser <keir.xen@xxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] xen: increase static dmesg buffer to 64K
From: Olaf Hering <olaf@xxxxxxxxx>
Date: Mon, 18 Jul 2011 10:45:12 +0200
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, Jan Beulich <JBeulich@xxxxxxxxxx>
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On Mon, Jul 18, Keir Fraser wrote:

> On 18/07/2011 09:16, "Olaf Hering" <olaf@xxxxxxxxx> wrote:
> > I think conring_size= should be evaluated very early. Is there a way to
> > allocate a range of mfns very early which can then be used for the dmesg
> > buffer?
> Are you actually losing messages because you can't allocate the larger
> console ring early enough? It seems a bit unlikely, but possible I suppose.

Yes, I was booting with conring_size=, but the bulk of messages were
already printed at that point. My 80 cpu testbox had 24K in dmesg buffer
with my patch.

> Anyhow, the normal memory allocator is available plenty early enough. You'd
> just need to do the allocation earlier than console_init_postirq(). Sometime
> soon after the call to end_boot_allocator() would work nicely.

I will put that on my TODO list, and look at your and Jans suggestion to
move the dmesg buffer allocation earlier.


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