Messages in this thread Patch in this message | | | Date | Tue, 13 Jul 2010 15:11:37 +0100 | Subject | Re: [2.6.35-rc5] select useful number of entries for DMA debugging v3... | From | Daniel J Blueman <> |
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On 12 July 2010 15:39, John Stoffel <john@stoffel.org> wrote: >>>>>> "Daniel" == Daniel J Blueman <daniel.blueman@gmail.com> writes: > > Daniel> On 11 July 2010 12:54, Daniel J Blueman <daniel.blueman@gmail.com> wrote: >>> On 10 July 2010 16:43, Joerg Roedel <joro@8bytes.org> wrote: >>>> On Sat, Jul 10, 2010 at 03:52:04PM +0100, Daniel J Blueman wrote: >>>>> On 9 July 2010 22:33, Linus Torvalds <torvalds@linux-foundation.org> wrote: >>>>> > On Mon, Jul 5, 2010 at 1:35 AM, Daniel J Blueman >>>>> > <daniel.blueman@gmail.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. >>> >>> 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. > > Daniel> How about something like this? If you think ~18800 entries on a 1GB > Daniel> system is better, let me know and I'll quickly respin. The calculation > Daniel> seems reasonable for other arches. > > Daniel> When booting 2.6.35-rc3 on some different x86 boxes with DMA debugging > Daniel> enabled, I've seen consistent exhaustion of the allocated entries during > Daniel> boot, giving 'DMA-API: debugging out of memory - disabling'. > > Daniel> Increase the default number of entries to allow DMA debugging again, but > Daniel> assign a reasonable lower limit for systems with less memory (eg ~37600 > Daniel> entries on a 1GB system), to prevent excessive use. > > Daniel> Signed-off-by: Daniel J Blueman <daniel.blueman@gmail.com> > > Daniel> diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c > Daniel> index a4ac764..0766fcf 100644 > Daniel> --- a/arch/x86/kernel/pci-dma.c > Daniel> +++ b/arch/x86/kernel/pci-dma.c > Daniel> @@ -52,7 +52,7 @@ struct device x86_dma_fallback_dev = { > Daniel> EXPORT_SYMBOL(x86_dma_fallback_dev); > > Daniel> /* Number of entries preallocated for DMA-API debugging */ > Daniel> -#define PREALLOC_DMA_DEBUG_ENTRIES 32768 > Daniel> +#define PREALLOC_DMA_DEBUG_ENTRIES 65536 > > Daniel> int dma_set_mask(struct device *dev, u64 mask) > Daniel> { > Daniel> diff --git a/lib/dma-debug.c b/lib/dma-debug.c > Daniel> index ba8b670..2d1f965 100644 > Daniel> --- a/lib/dma-debug.c > Daniel> +++ b/lib/dma-debug.c > Daniel> @@ -736,6 +736,10 @@ void dma_debug_init(u32 num_entries) > > Daniel> if (req_entries) > Daniel> num_entries = req_entries; > Daniel> + else > Daniel> + /* for systems with less memory, limit to a proportional amount of memory */ > Daniel> + /* eg 1GB memory, 4KB pages ~ 37600 entries */ > Daniel> + num_entries = min(num_entries, (unsigned int)(totalram_pages >> > Daniel> (PAGE_SHIFT - 10))); > > Daniel> if (prealloc_memory(num_entries) != 0) { > Daniel> pr_err("DMA-API: debugging out of memory error - disabled\n"); > > Maybe you could update this to mention the kernel parameter > "dma_debug_entries=xxxxx" so that people could use to increase this > value? It would make it simpler and easier to find it it's logged > nicely?
Good comment. Fixed checkpatch compliance and rediffed against 2.6.35-rc5. Linus/Ingo - is this more acceptable?
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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 ~38000 entries on a 1GB system), to prevent excessive use.
Signed-off-by: Daniel J Blueman <daniel.blueman@gmail.com>
diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c index 4b7e3d8..5ff7f12 100644 --- a/arch/x86/kernel/pci-dma.c +++ b/arch/x86/kernel/pci-dma.c @@ -53,7 +53,7 @@ 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 01e6427..b689ac7 100644 --- a/lib/dma-debug.c +++ b/lib/dma-debug.c @@ -487,7 +487,8 @@ static int prealloc_memory(u32 num_entries) num_free_entries = num_entries; min_free_entries = num_entries;
- pr_info("DMA-API: preallocated %d debug entries\n", num_entries); + pr_info("DMA-API: preallocated %d debug entries; boot with " + "dma_debug_entries=N to change\n", num_entries);
return 0;
@@ -736,6 +737,13 @@ 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 ~ 38000 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/
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