Re: Suspicious error for CMA stress test

Joonsoo Kim
2016-03-03T07:42:17Z

2016-03-03 10:25 GMT+09:00 Laura Abbott <labbott@redhat.com>:
> (cc -mm and Joonsoo Kim)
>
>
> On 03/02/2016 05:52 AM, Hanjun Guo wrote:
>>
>> Hi,
>>
>> I came across a suspicious error for CMA stress test:
>>
>> Before the test, I got:
>> -bash-4.3# cat /proc/meminfo | grep Cma
>> CmaTotal: 204800 kB
>> CmaFree: 195044 kB
>>
>>
>> After running the test:
>> -bash-4.3# cat /proc/meminfo | grep Cma
>> CmaTotal: 204800 kB
>> CmaFree: 6602584 kB
>>
>> So the freed CMA memory is more than total..
>>
>> Also the the MemFree is more than mem total:
>>
>> -bash-4.3# cat /proc/meminfo
>> MemTotal: 16342016 kB
>> MemFree: 22367268 kB
>> MemAvailable: 22370528 kB
>>
>> Here is the kernel module doing the stress test below (if the test case
>> is wrong, correct me), any help would be great appreciated.
>>
>> The test is running on ARM64 platform (hisilicon D02) with 4.4 kernel, I
>> think
>> the 4.5-rc is the same as I didn't notice the updates for it.
>>
>> int malloc_dma(void *data)
>> {
>> void *vaddr;
>> struct platform_device * pdev=(struct platform_device*)data;
>> dma_addr_t dma_handle;
>> int i;
>>
>> for(i=0; i<1000; i++) {
>> vaddr=dma_alloc_coherent(&pdev->dev, malloc_size, &dma_handle,
>> GFP_KERNEL);
>> if (!vaddr)
>> pr_err("alloc cma memory failed!\n");
>>
>> mdelay(1);
>>
>> if (vaddr)
>> dma_free_coherent(&pdev->dev,malloc_size,vaddr,
>> dma_handle);
>> }
>> pr_info("alloc free cma memory success return!\n");
>> return 0;
>> }
>>
>> static int dma_alloc_coherent_init(struct platform_device *pdev)
>> {
>> int i;
>>
>> for(i=0; i<100; i++) {
>> task[i] = kthread_create(malloc_dma,pdev,"malloc_dma_%d",i);
>> if(!task[i]) {
>> printk("kthread_create faile %d\n",i);
>> continue;
>> }
>> wake_up_process(task[i]);
>> }
>> return 0;
>> }
>>
>> Thanks
>> Hanjun
>>
>> The whole /proc/meminfo:
>>
>> -bash-4.3# cat /proc/meminfo
>> MemTotal: 16342016 kB
>> MemFree: 22367268 kB
>> MemAvailable: 22370528 kB
>> Buffers: 4292 kB
>> Cached: 36444 kB
>> SwapCached: 0 kB
>> Active: 23564 kB
>> Inactive: 25360 kB
>> Active(anon): 8424 kB
>> Inactive(anon): 64 kB
>> Active(file): 15140 kB
>> Inactive(file): 25296 kB
>> Unevictable: 0 kB
>> Mlocked: 0 kB
>> SwapTotal: 0 kB
>> SwapFree: 0 kB
>> Dirty: 0 kB
>> Writeback: 0 kB
>> AnonPages: 8196 kB
>> Mapped: 16448 kB
>> Shmem: 296 kB
>> Slab: 26832 kB
>> SReclaimable: 6300 kB
>> SUnreclaim: 20532 kB
>> KernelStack: 3088 kB
>> PageTables: 404 kB
>> NFS_Unstable: 0 kB
>> Bounce: 0 kB
>> WritebackTmp: 0 kB
>> CommitLimit: 8171008 kB
>> Committed_AS: 34336 kB
>> VmallocTotal: 258998208 kB
>> VmallocUsed: 0 kB
>> VmallocChunk: 0 kB
>> AnonHugePages: 0 kB
>> CmaTotal: 204800 kB
>> CmaFree: 6602584 kB
>> HugePages_Total: 0
>> HugePages_Free: 0
>> HugePages_Rsvd: 0
>> HugePages_Surp: 0
>> Hugepagesize: 2048 kB
>>
>
>
> I played with this a bit and can see the same problem. The sanity
> check of CmaFree < CmaTotal generally triggers in
> __move_zone_freepage_state in unset_migratetype_isolate.
> This also seems to be present as far back as v4.0 which was the
> first version to have the updated accounting from Joonsoo.
> Were there known limitations with the new freepage accounting,
> Joonsoo?

I don't know. I also played with this and looks like there is
accounting problem, however, for my case, number of free page is slightly less
than total. I will take a look.

Hanjun, could you tell me your malloc_size? I tested with 1 and it doesn't
look like your case.

Thanks.