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Date: Mon, 02 Jan 2017 14:42:33 +0900
From: Jaewon Kim <jaewon31.kim@...sung.com>
To: Michal Nazarewicz <mina86@...a86.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 2017년 01월 02일 06:59, Michal Nazarewicz wrote:
> On Fri, Dec 30 2016, Michal Hocko wrote:
>> On Fri 30-12-16 16:24:46, Jaewon Kim wrote:
>> [...]
>>> >From 7577cc94da3af27907aa6eec590d2ef51e4b9d80 Mon Sep 17 00:00:00 2001
>>> From: Jaewon Kim <jaewon31.kim@...sung.com>
>>> Date: Thu, 29 Dec 2016 11:00:16 +0900
>>> Subject: [PATCH] mm: cma: print allocation failure reason and bitmap status
>>>
>>> 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 try 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.
>>> [ 13.250961] [1: Binder:715_1: 846] cma: cma_alloc: alloc failed, req-size: 256 pages, ret: -12
>>> Avabile pages also will be shown if CONFIG_CMA_DEBUG is enabled
>>> [ 13.251052] [1: Binder:715_1: 846] cma: number of available pages: 4@...+7@...+7@...+8@...+38@...+166@...4+127@...1=>357 pages, total: 2048 pages
>> please mention how to interpret this information.
Thank you Michal Hocko. I added like this
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.
>>
>> some more style suggestions below
>>> Signed-off-by: Jaewon Kim <jaewon31.kim@...sung.com>
> Acked-by: Michal Nazarewicz <mina86@...a86.com>
Thank you I added your Ack
Acked-by: Michal Nazarewicz <mina86@...a86.com>
>>> ---
>>> mm/cma.c | 29 ++++++++++++++++++++++++++++-
>>> 1 file changed, 28 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/mm/cma.c b/mm/cma.c
>>> index c960459..1bcd9db 100644
>>> --- a/mm/cma.c
>>> +++ b/mm/cma.c
>>> @@ -369,7 +369,7 @@ 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;
>>> @@ -427,6 +427,33 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align)
>>> trace_cma_alloc(pfn, page, count, align);
>>>
>>> pr_debug("%s(): returned %p\n", __func__, page);
> This line should be moved after the ‘if (ret != 0)’ block, i.e. just
> before return.
Thank you Michal Nazarewicz
I moved the pr_debug right before return
pr_debug("%s(): returned %p\n", __func__, page);
return page;
>>> +
>>> + if (ret != 0)
>> you can simply do
>> if (!ret) {
Thank you
I changed like this, it should be if(ret) rather than if(!ret)
+ if (ret) {
+ pr_info("%s: alloc failed, req-size: %zu pages, ret: %d\n",
+ __func__, count, ret);
+ debug_show_cma_areas(cma);
+ }
>>
>> pr_info("%s: alloc failed, req-size: %zu pages, ret: %d\n",
>> __func__, count, ret);
>> debug_show_cma_areas();
>> }
>>
>> return page;
>>
>> static void debug_show_cma_areas(void)
>> {
>> #ifdef CONFIG_CMA_DEBUG
>> unsigned int nr, nr_total = 0;
>> unsigned long next_set_bit;
>>
>> mutex_lock(&cma->lock);
>> pr_info("number of available pages: ");
>> start = 0;
>> for (;;) {
>> bitmap_no = find_next_zero_bit(cma->bitmap, cma->count, start);
>> if (bitmap_no >= cma->count)
>> break;
>> next_set_bit = find_next_bit(cma->bitmap, cma->count, bitmap_no);
>> nr = next_set_bit - bitmap_no;
>> pr_cont("%s%u@%lu", nr_total ? "+" : "", nr, bitmap_no);
>> nr_total += nr;
>> start = bitmap_no + nr;
>> }
>> pr_cont("=>%u pages, total: %lu pages\n", nr_total, cma->count);
> Perhaps:
> pr_cont("=> %u free of %lu total pages\n", nr_total, cma->count);
Thank you I will take this way.
+ pr_cont("=> %u free of %lu total pages\n", nr_total, cma->count);
> or shorter (but more cryptic):
> pr_cont("=> %u/%lu pages\n", nr_total, cma->count);
>
>> mutex_unlock(&cma->lock);
>> #endif
>> }
> Actually, Linux style is more like:
>
> #ifdef CONFIG_CMA_DEBUG
> static void cma_debug_show_areas()
> {
> …
> }
> #else
> static inline void cma_debug_show_areas() { }
> #endif
Thank you I will take this way. FYI struct cma address should be passed as a argument.
+#ifdef CONFIG_CMA_DEBUG
+static void debug_show_cma_areas(struct cma *cma)
+{
...
+#else
+static inline void debug_show_cma_areas(struct cma *cma) { }
+#endif
>> --
>> Michal Hocko
>> SUSE Labs
Thank you all of you.
Let me reattach my full patch to be clear.
Let me know if I resend this as a new mail thread.
>From 03bf46bac222587f66fe9935a7879da30ff42cff Mon Sep 17 00:00:00 2001
From: Jaewon Kim <jaewon31.kim@...sung.com>
Date: Thu, 29 Dec 2016 11:00:16 +0900
Subject: [PATCH] mm: cma: print allocation failure reason and bitmap status
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)
+{
+ 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;
}
--
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