linux-kernel - Re: [PATCH 1/3] swiotlb: Warn on allocation failure in swiotlb_alloc

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Date:	Wed, 3 Dec 2014 11:26:52 +0100
From:	Joerg Roedel <jroedel@...e.de>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:	Joerg Roedel <joro@...tes.org>, Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] swiotlb: Warn on allocation failure in
 swiotlb_alloc_coherent

On Tue, Dec 02, 2014 at 01:46:15PM -0500, Konrad Rzeszutek Wilk wrote:
> On Tue, Dec 02, 2014 at 03:41:22PM +0100, Joerg Roedel wrote:
> > On Mon, Dec 01, 2014 at 03:28:03PM -0500, Konrad Rzeszutek Wilk wrote:
> > > On Fri, Nov 28, 2014 at 12:29:07PM +0100, Joerg Roedel wrote:
> > > > From: Joerg Roedel <jroedel@...e.de>
> > > > 
> > > > Print a warning when all allocation tries have been failed
> > > > and the function is about to return NULL. This prepares for
> > > > calling the function with __GFP_NOWARN to suppress
> > > > allocation failure warnings before all fall-backs have
> > > > failed.
> > > 
> > > This can be quite noisy. Especially the dump-stack.
> > 
> > Well, this is as noisy as the dump_stack()s from the page-allocator when
> > the first allocation try fails. The goal of the first two patches in
> 
> Right, on the first allocation. Subsequent allocations won't be so noisy
> in the page-allocator (I think?).

>From the code in mm/page_alloc.c (function warn_alloc_failed) it doesn't
look like a one-time warning. The dmesg I have seen from a failing
kernel also shows a lot of these messages.

So having the warning at the end of swiotlb_alloc_coherent won't be any
more noisy than the (removed) warnings from the page allocator.


	Joerg

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