Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754105Ab0GKNAG (ORCPT ); Sun, 11 Jul 2010 09:00:06 -0400 Received: from mail-gx0-f174.google.com ([209.85.161.174]:58796 "EHLO mail-gx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752452Ab0GKNAE convert rfc822-to-8bit (ORCPT ); Sun, 11 Jul 2010 09:00:04 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=H5UktRhSyiw5vhOrZ0pe0H34cfG4xOu4f8Bxi2xlPW02bMf3PGlft5HOjxrhPDr8A6 Qi0FKuUdyK8Q0/aNQY1ayirTSWO0T8VsxpASta/VaFnqkdqtbjm9ARe0c79MCUMfKX1e aOXIivgkFcO8bVaRBV5iSOFCE3t/hJqnpCJu0= MIME-Version: 1.0 In-Reply-To: References: <20100710154331.GF10080@8bytes.org> Date: Sun, 11 Jul 2010 14:00:03 +0100 Message-ID: Subject: Re: [2.6.35-rc3] select useful number of entries for DMA debugging... From: Daniel J Blueman To: Joerg Roedel Cc: Linus Torvalds , Linux Kernel , Ingo Molnar Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4021 Lines: 90 On 11 July 2010 12:54, Daniel J Blueman wrote: > On 10 July 2010 16:43, Joerg Roedel wrote: >> On Sat, Jul 10, 2010 at 03:52:04PM +0100, Daniel J Blueman wrote: >>> On 9 July 2010 22:33, Linus Torvalds wrote: >>> > On Mon, Jul 5, 2010 at 1:35 AM, Daniel J Blueman >>> > 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. > > I have 4GB. Since this change is specific to x86, I guess the only > corner case we need to protect from this change is developers on small > x86 embedded systems such as MIDs, so lowering the allocated size on > <1GB systems makes sense. How about something like this? If you think ~18800 entries on a 1GB system is better, let me know and I'll quickly respin. The calculation seems reasonable for other arches. When booting 2.6.35-rc3 on some different x86 boxes with DMA debugging enabled, I've seen consistent exhaustion of the allocated entries during boot, giving 'DMA-API: debugging out of memory - disabling'. Increase the default number of entries to allow DMA debugging again, but assign a reasonable lower limit for systems with less memory (eg ~37600 entries on a 1GB system), to prevent excessive use. Signed-off-by: Daniel J Blueman diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c index a4ac764..0766fcf 100644 --- a/arch/x86/kernel/pci-dma.c +++ b/arch/x86/kernel/pci-dma.c @@ -52,7 +52,7 @@ struct device x86_dma_fallback_dev = { EXPORT_SYMBOL(x86_dma_fallback_dev); /* Number of entries preallocated for DMA-API debugging */ -#define PREALLOC_DMA_DEBUG_ENTRIES 32768 +#define PREALLOC_DMA_DEBUG_ENTRIES 65536 int dma_set_mask(struct device *dev, u64 mask) { diff --git a/lib/dma-debug.c b/lib/dma-debug.c index ba8b670..2d1f965 100644 --- a/lib/dma-debug.c +++ b/lib/dma-debug.c @@ -736,6 +736,10 @@ void dma_debug_init(u32 num_entries) if (req_entries) num_entries = req_entries; + else + /* for systems with less memory, limit to a proportional amount of memory */ + /* eg 1GB memory, 4KB pages ~ 37600 entries */ + num_entries = min(num_entries, (unsigned int)(totalram_pages >> (PAGE_SHIFT - 10))); if (prealloc_memory(num_entries) != 0) { pr_err("DMA-API: debugging out of memory error - disabled\n"); -- Daniel J Blueman -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/