Messages in this thread | | | Date | Wed, 18 May 2016 21:15:13 +0800 | Subject | Re: malloc() size in CMA region seems to be aligned to CMA_ALIGNMENT | From | lunar12 lunartwix <> |
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2016-05-18 16:48 GMT+08:00 Michal Hocko <mhocko@kernel.org>: > [CC linux-mm and some usual suspects] > > On Tue 17-05-16 23:37:55, lunar12 lunartwix wrote: >> A 4MB dma_alloc_coherent in kernel after malloc(2*1024) 40 times in >> CMA region by user space will cause an error on our ARM 3.18 kernel >> platform with a 32MB CMA. >> >> It seems that the malloc in CMA region will be aligned to >> CMA_ALIGNMENT everytime even if the requested malloc size is very >> small so the CMA region is not available after the malloc operations. >> >> Is there any configuraiton that can change this behavior?? >> >> Thanks >> >> Cheers >> Ken > > -- > Michal Hocko > SUSE Labs
Update more information and any comment would be very appreciated
CMA region (from boot message): Reserved memory: created CMA memory pool at 0x22e00000, size 80 MiB
User space test program:
do {
addr = malloc(2*1024); memset((void *)addr,2*1024,0x5A); vaddr=(unsigned int)addr;
//get_user_page & page_to_phys in kernel ioctl(devfd, IOCTL_MSYS_USER_TO_PHYSICAL, &addr)
count++; paddr=(unsigned int)addr;
if(paddr>0x22E00000) { printf("USR:0x%08X 0x%08X %d\n",vaddr,paddr,count); } } while(addr!=NULL);
System print out:
USR:0x0164B248 0x27C00000 11337 USR:0x0164BA50 0x27C00000 11338 USR:0x0164C258 0x27800000 11339 USR:0x0164CA60 0x27800000 11340 USR:0x0164D268 0x27600000 11341 USR:0x0164DA70 0x27600000 11342 USR:0x0164E278 0x27400000 11343 USR:0x0164EA80 0x27400000 11344 USR:0x0164F288 0x27200000 11345 USR:0x0164FA90 0x27200000 11346 .... It seems that an 2MB CMA would be occpuied every 2 malloc()
Cheers Ken
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