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Date: Mon, 02 Jan 2017 07:46:16 +0100 From: Michal Nazarewicz <mina86@...a86.com> To: Jaewon Kim <jaewon31.kim@...sung.com>, Michal Hocko <mhocko@...nel.org> Cc: gregkh@...uxfoundation.org, akpm@...ux-foundation.org, labbott@...hat.com, m.szyprowski@...sung.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org, jaewon31.kim@...il.com Subject: Re: [PATCH] mm: cma: print allocation failure reason and bitmap status On Mon, Jan 02 2017, Jaewon Kim wrote: > There are many reasons of CMA allocation failure such as EBUSY, ENOMEM, EINTR. > But we did not know error reason so far. This patch prints the error value. > > Additionally if CONFIG_CMA_DEBUG is enabled, this patch shows bitmap status to > know available pages. Actually CMA internally tries on all available regions > because some regions can be failed because of EBUSY. Bitmap status is useful to > know in detail on both ENONEM and EBUSY; > ENOMEM: not tried at all because of no available region > it could be too small total region or could be fragmentation issue > EBUSY: tried some region but all failed > > This is an ENOMEM example with this patch. > [ 12.415458] [2: Binder:714_1: 744] cma: cma_alloc: alloc failed, req-size: 256 pages, ret: -12 > If CONFIG_CMA_DEBUG is enabled, avabile pages also will be shown as concatenated > size@...ition format. So 4@572 means that there are 4 available pages at 572 > position starting from 0 position. > [ 12.415503] [2: Binder:714_1: 744] cma: number of available pages: 4@...+7@...+7@...+8@...+38@...+166@...4+127@...1=> 357 free of 2048 total pages > > Signed-off-by: Jaewon Kim <jaewon31.kim@...sung.com> > Acked-by: Michal Nazarewicz <mina86@...a86.com> > --- > mm/cma.c | 34 +++++++++++++++++++++++++++++++++- > 1 file changed, 33 insertions(+), 1 deletion(-) > > diff --git a/mm/cma.c b/mm/cma.c > index c960459..9e037541 100644 > --- a/mm/cma.c > +++ b/mm/cma.c > @@ -353,6 +353,32 @@ int __init cma_declare_contiguous(phys_addr_t base, > return ret; > } > > +#ifdef CONFIG_CMA_DEBUG > +static void debug_show_cma_areas(struct cma *cma) Make it ‘cma_debug_show_areas’. All other functions have ‘cma’ as prefix so that’s more consistent. > +{ > + unsigned long next_zero_bit, next_set_bit; > + unsigned long start = 0; > + unsigned int nr_zero, nr_total = 0; > + > + mutex_lock(&cma->lock); > + pr_info("number of available pages: "); > + for (;;) { > + next_zero_bit = find_next_zero_bit(cma->bitmap, cma->count, start); > + if (next_zero_bit >= cma->count) > + break; > + next_set_bit = find_next_bit(cma->bitmap, cma->count, next_zero_bit); > + nr_zero = next_set_bit - next_zero_bit; > + pr_cont("%s%u@%lu", nr_total ? "+" : "", nr_zero, next_zero_bit); > + nr_total += nr_zero; > + start = next_zero_bit + nr_zero; > + } > + pr_cont("=> %u free of %lu total pages\n", nr_total, cma->count); > + mutex_unlock(&cma->lock); > +} > +#else > +static inline void debug_show_cma_areas(struct cma *cma) { } > +#endif > + > /** > * cma_alloc() - allocate pages from contiguous area > * @cma: Contiguous memory region for which the allocation is performed. > @@ -369,7 +395,7 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align) > unsigned long start = 0; > unsigned long bitmap_maxno, bitmap_no, bitmap_count; > struct page *page = NULL; > - int ret; > + int ret = -ENOMEM; > > if (!cma || !cma->count) > return NULL; > @@ -426,6 +452,12 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align) > > trace_cma_alloc(pfn, page, count, align); > > + if (ret) { > + pr_info("%s: alloc failed, req-size: %zu pages, ret: %d\n", > + __func__, count, ret); > + debug_show_cma_areas(cma); > + } > + > pr_debug("%s(): returned %p\n", __func__, page); > return page; > } > -- > -- Best regards ミハウ “𝓶𝓲𝓷𝓪86” ナザレヴイツ «If at first you don’t succeed, give up skydiving»
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