Messages in this thread | | | Subject | Re: [PATCH] dma-debug: Kconfig for PREALLOC_DMA_DEBUG_ENTRIES | From | Robin Murphy <> | Date | Fri, 30 Nov 2018 19:39:50 +0000 |
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On 30/11/2018 17:54, Qian Cai wrote: > The amount of DMA mappings from Hisilicon HNS ethernet devices is huge, > so it could trigger "DMA-API: debugging out of memory - disabling". > > hnae_get_handle [1] > hnae_init_queue > hnae_init_ring > hnae_alloc_buffers [2] > debug_dma_map_page > dma_entry_alloc > > [1] for (i = 0; i < handle->q_num; i++) > [2] for (i = 0; i < ring->desc_num; i++) > > On this Huawei TaiShan 2280 aarch64 server, it has reached the limit > already, > > 4 (ports) x 16 (handles) x 1024 (rings) = 65536 > > Added a Kconfig entry for PREALLOC_DMA_DEBUG_ENTRIES, so make it easier > for users to deal with special cases like this. > > Signed-off-by: Qian Cai <cai@gmx.us> > --- > kernel/dma/debug.c | 9 ++------- > lib/Kconfig.debug | 9 +++++++++ > 2 files changed, 11 insertions(+), 7 deletions(-)
Oh, right, the arch overrides actually got cleaned up already. I'd forgotten that...
> diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c > index 231ca4628062..3752fb23f72f 100644 > --- a/kernel/dma/debug.c > +++ b/kernel/dma/debug.c > @@ -41,11 +41,6 @@ > #define HASH_FN_SHIFT 13 > #define HASH_FN_MASK (HASH_SIZE - 1) > > -/* allow architectures to override this if absolutely required */ > -#ifndef PREALLOC_DMA_DEBUG_ENTRIES > -#define PREALLOC_DMA_DEBUG_ENTRIES (1 << 16) > -#endif > - > enum { > dma_debug_single, > dma_debug_page, > @@ -132,7 +127,7 @@ static u32 min_free_entries; > static u32 nr_total_entries; > > /* number of preallocated entries requested by kernel cmdline */ > -static u32 nr_prealloc_entries = PREALLOC_DMA_DEBUG_ENTRIES; > +static u32 nr_prealloc_entries = CONFIG_PREALLOC_DMA_DEBUG_ENTRIES; > > /* debugfs dentry's for the stuff above */ > static struct dentry *dma_debug_dent __read_mostly; > @@ -1063,7 +1058,7 @@ static __init int dma_debug_entries_cmdline(char *str) > if (!str) > return -EINVAL; > if (!get_option(&str, &nr_prealloc_entries)) > - nr_prealloc_entries = PREALLOC_DMA_DEBUG_ENTRIES; > + nr_prealloc_entries = CONFIG_PREALLOC_DMA_DEBUG_ENTRIES; > return 0; > } > > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > index 1af29b8224fd..2c281edcb5ad 100644 > --- a/lib/Kconfig.debug > +++ b/lib/Kconfig.debug > @@ -1659,6 +1659,15 @@ config DMA_API_DEBUG > > If unsure, say N. > > +config PREALLOC_DMA_DEBUG_ENTRIES > + int "Preallocated DMA-API debugging entries" > + depends on DMA_API_DEBUG > + default 65536
I was assuming the point was to also add something like
default 131072 if HNS_ENET
so that DMA debug doesn't require too much thought from the user. If they still have to notice the overflow message and empirically figure out a value that does work, rebuilding the kernel each time is far less convenient than simply adding "dma_debug_entries=..." to their kernel command line and rebooting, which they can do today. If they do already know up-front that the default will need overriding and what the appropriate value is, then the command line still seems seems just as convenient.
Robin.
> + help > + The number of preallocated entries for DMA-API debugging code. One > + entry is required per DMA-API allocation. Increase this if the DMA-API > + debugging code disables itself because the default is too low. > + > config DMA_API_DEBUG_SG > bool "Debug DMA scatter-gather usage" > default y >
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