> -----Original Message----- > From: linux-arm-kernel-bounces@xxxxxxxxxxxxxxxxxxx [mailto:linux-arm-kernel- > bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Hiremath, Vaibhav > Sent: Thursday, December 17, 2009 11:09 AM > To: linux@xxxxxxxxxxxxxxxx > Cc: linux-mm@xxxxxxxxx; linux-omap@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > Subject: CPU consumption is going as high as 95% on ARM Cortex A8 > > Hi, > > I am seeing some strange behavior while accessing buffers through User Space (mapped using mmap call) > > Background :- > ------------ > Platform - TI AM3517 > CPU - ARM Cortex A8 > > root@am3517-evm:~# > root@am3517-evm:~# cat /proc/cpuinfo > Processor : ARMv7 Processor rev 7 (v7l) > BogoMIPS : 499.92 > Features : swp half thumb fastmult vfp edsp neon vfpv3 > CPU implementer : 0x41 > CPU architecture: 7 > CPU variant : 0x1 > CPU part : 0xc08 > CPU revision : 7 > Hardware : OMAP3517/AM3517 EVM > Revision : 0020 > Serial : 0000000000000000 > root@omap3517-evm:~# > > > Issue/Usage :- > ------------- > The V4l2-Capture driver captures the data from video decoder into buffer and the application does > some processing on this buffer. The mmap implementation can be found at drivers/media/video/videobuf- > dma-contig.c, function__videobuf_mmap_mapper(). > > Observation - > The CPU consumption goes as high as 95% on read buffer operation, please note that write operation on > these buffers also gives 60-70% CPU consumption. (Using memcpy/memset API's for read and write > operation). > > Some more inputs :- > ------------------ > - If I specify PAGE_READONLY or PAGE_SHARED (actual flag is L_PTE_USER) while mapping the buffer to > UserSpace in mmap system call, the CPU consumption goes down to expected value (20-27%). > Then I reached till the function cpu_v7_set_pte_ext, where we are configuring level 2 translation > table entries, which makes use of these flags. > > - Below is the value of r0, r1 and r2 register (ptep, pteval, ext) in both the cases - > > > Without PAGE_READONLY/PAGE_SHARED > > ptep - cfb5de10, pte - 8d200383, ext - 800 > ptep - cfb5de14, pte - 8d201383, ext - 800 Which kernel version is this? Can you please also give values of PRRR, NMRR and SCTLR -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
