| Message ID | 20190320060829.9144-1-zbestahu@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm/cma: fix the bitmap status to show failed allocation reason | expand |
On Wed, 20 Mar 2019 14:08:29 +0800 Yue Hu <zbestahu@gmail.com> wrote: > Currently one bit in cma bitmap represents number of pages rather than > one page, cma->count means cma size in pages. So to find available pages > via find_next_zero_bit()/find_next_bit() we should use cma size not in > pages but in bits although current free pages number is correct due to > zero value of order_per_bit. Once order_per_bit is changed the bitmap > status will be incorrect. When fixing a bug, please always describe the end-user visible runtime effects of that bug?
On Wed, 20 Mar 2019 15:12:45 -0700 Andrew Morton <akpm@linux-foundation.org> wrote: > On Wed, 20 Mar 2019 14:08:29 +0800 Yue Hu <zbestahu@gmail.com> wrote: > > > Currently one bit in cma bitmap represents number of pages rather than > > one page, cma->count means cma size in pages. So to find available pages > > via find_next_zero_bit()/find_next_bit() we should use cma size not in > > pages but in bits although current free pages number is correct due to > > zero value of order_per_bit. Once order_per_bit is changed the bitmap > > status will be incorrect. > > When fixing a bug, please always describe the end-user visible runtime > effects of that bug? > Hi Andrew, From perspective of bitmap function, the size input is not correct. It will affect the available pages at some position to debug the failure issue. This is an example with order_per_bit = 1 Before this change: [ 4.120060] cma: number of available pages: 1@93+4@108+7@121+7@137+7@153+7@169+7@185+7@201+3@213+3@221+3@229+3@237+3@245+3@253+3@261+3@269+3@277+3@285+3@293+3@301+3@309+3@317+3@325+19@333+15@369+512@512=> 638 free of 1024 total pages After this change: [ 4.143234] cma: number of available pages: 2@93+8@108+14@121+14@137+14@153+14@169+14@185+14@201+6@213+6@221+6@229+6@237+6@245+6@253+6@261+6@269+6@277+6@285+6@293+6@301+6@309+6@317+6@325+38@333+30@369=> 252 free of 1024 total pages Obviously the bitmap status before is incorrect, i can add this effect describtion in v2, but seems the patch has been merged? Thx.
On Thu, 21 Mar 2019 10:17:21 +0800 Yue Hu <zbestahu@gmail.com> wrote: > >From perspective of bitmap function, the size input is not correct. It will > affect the available pages at some position to debug the failure issue. > > This is an example with order_per_bit = 1 > > Before this change: > [ 4.120060] cma: number of available pages: 1@93+4@108+7@121+7@137+7@153+7@169+7@185+7@201+3@213+3@221+3@229+3@237+3@245+3@253+3@261+3@269+3@277+3@285+3@293+3@301+3@309+3@317+3@325+19@333+15@369+512@512=> 638 free of 1024 total pages > > After this change: > [ 4.143234] cma: number of available pages: 2@93+8@108+14@121+14@137+14@153+14@169+14@185+14@201+6@213+6@221+6@229+6@237+6@245+6@253+6@261+6@269+6@277+6@285+6@293+6@301+6@309+6@317+6@325+38@333+30@369=> 252 free of 1024 total pages > > Obviously the bitmap status before is incorrect, i can add this effect describtion > in v2, but seems the patch has been merged? Thanks, I updated the changelog.
diff --git a/mm/cma.c b/mm/cma.c index 5809bbe..6a7aa05 100644 --- a/mm/cma.c +++ b/mm/cma.c @@ -367,23 +367,26 @@ int __init cma_declare_contiguous(phys_addr_t base, #ifdef CONFIG_CMA_DEBUG static void cma_debug_show_areas(struct cma *cma) { - unsigned long next_zero_bit, next_set_bit; + unsigned long next_zero_bit, next_set_bit, nr_zero; unsigned long start = 0; - unsigned int nr_zero, nr_total = 0; + unsigned long nr_part, nr_total = 0; + unsigned long nbits = cma_bitmap_maxno(cma); 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) + next_zero_bit = find_next_zero_bit(cma->bitmap, nbits, start); + if (next_zero_bit >= nbits) break; - next_set_bit = find_next_bit(cma->bitmap, cma->count, next_zero_bit); + next_set_bit = find_next_bit(cma->bitmap, nbits, 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; + nr_part = nr_zero << cma->order_per_bit; + pr_cont("%s%lu@%lu", nr_total ? "+" : "", nr_part, + next_zero_bit); + nr_total += nr_part; start = next_zero_bit + nr_zero; } - pr_cont("=> %u free of %lu total pages\n", nr_total, cma->count); + pr_cont("=> %lu free of %lu total pages\n", nr_total, cma->count); mutex_unlock(&cma->lock); } #else