On 05/12/2014 08:46 AM, Jeff Moyer wrote: > Jens Axboe <axboe@xxxxxx> writes: > >> Hi, >> >> In some testing I ran today, we end up spending 40% of the time in >> filemap_check_errors(). That smells fishy. Looking further, this is >> basically what happens: >> >> blkdev_aio_read() >> generic_file_aio_read() >> filemap_write_and_wait_range() >> if (!mapping->nr_pages) >> filemap_check_errors() >> >> and filemap_check_errors() always attempts two test_and_clear_bit() on >> the mapping flags, thus dirtying it for every single invocation. The >> patch below tests each of these bits before clearing them, avoiding this >> issue. In my test case (4-socket box), performance went from 1.7M IOPS >> to 4.0M IOPS. > > It might help to use the word cacheline somewhere in here. ;-) Out of I thought that was self-evident, but yes, I could add that :-) > curiosity, what workload were you running? Nothing fancy, just some fio jobs that spread over two nodes. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>