On Wed, Nov 18, 2015 at 08:52:59AM -0800, Dan Williams wrote: > On Wed, Nov 18, 2015 at 7:53 AM, Jeff Moyer <jmoyer@xxxxxxxxxx> wrote: > > Hi, > > > > When running the nvml library's test suite against an ext4 file system > > mounted with -o dax, I ran into an issue where many of the tests would > > simply timeout. The problem appears to be that the pmd fault handler > > never returns to userspace (the application is doing a memcpy of 512 > > bytes into pmem). Here's the 'perf report -g' output: > > > > - 88.30% 0.01% blk_non_zero.st libc-2.17.so [.] __memmove_ssse3_back > > - 88.30% __memmove_ssse3_back > > - 66.63% page_fault > > - 66.47% do_page_fault > > - 66.16% __do_page_fault > > - 63.38% handle_mm_fault > > - 61.15% ext4_dax_pmd_fault > > - 45.04% __dax_pmd_fault > > - 37.05% vmf_insert_pfn_pmd > > - track_pfn_insert > > - 35.58% lookup_memtype > > - 33.80% pat_pagerange_is_ram > > - 33.40% walk_system_ram_range > > - 31.63% find_next_iomem_res > > 21.78% strcmp > > > > And here's 'perf top': > > > > Samples: 2M of event 'cycles:pp', Event count (approx.): 56080150519 > > Overhead Shared Object Symbol > > 22.55% [kernel] [k] strcmp > > 20.33% [unknown] [k] 0x00007f9f549ef3f3 > > 10.01% [kernel] [k] native_irq_return_iret > > 9.54% [kernel] [k] find_next_iomem_res > > 3.00% [jbd2] [k] start_this_handle > > > > This is easily reproduced by doing the following: > > > > git clone https://github.com/pmem/nvml.git > > cd nvml > > make > > make test > > cd src/test/blk_non_zero > > ./blk_non_zero.static-nondebug 512 /path/to/ext4/dax/fs/testfile1 c 1073741824 w:0 > > > > I also ran the test suite against xfs, and the problem is not present > > there. However, I did not verify that the xfs tests were getting pmd > > faults. > > > > I'm happy to help diagnose the problem further, if necessary. > > Sysrq-t or sysrq-w dump? Also do you have the locking fix from Yigal? > > https://lists.01.org/pipermail/linux-nvdimm/2015-November/002842.html I was able to reproduce the issue in my setup with v4.3, and the patch from Yigal seems to solve it. Jeff, can you confirm? -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
