You may use options --create_on_open=1 --fallocate=none. By default FIO will prepare the file of the size (creates a sparse file) and then performs IO. The options --create_on_open=1 and --fallocate=none should skip the step. -- Srinivasa R Chamarthy On Fri, Apr 21, 2017 at 9:54 AM, Son Chu <son.ct@xxxxxxxxxxxxx> wrote: > Hi Sitsofe, > > Sorry if this email troubled you but I could not find any useful information for this. I am getting the question with fio page cache bypass option (direct=1 ioengine=libaio) > > I am using fio version 2.19 with command: > > fio --filename=/opt/test --direct=1 --rw=randrw --randrepeat=0 --ioengine=libaio --bs=4k --rwmixread=75 --iodepth=16 --numjobs=1 --name=4ktest --size=1G > > and i used cachestat tool from here to monitor: https://github.com/brendangregg/perf-tools > > The output was: > > Counting cache functions... Output every 1 seconds. > > HITS MISSES DIRTIES RATIO BUFFERS_MB CACHE_MB > > 1399 42 0 97.1% 2 31 > > 1408 0 0 100.0% 2 31 > > -68699 39 71478 100.1% 3 532 > > -21325 0 22886 100.0% 3 621 > > -19956 0 21492 100.0% 3 705 > > -13739 0 15254 100.0% 3 765 > > As far as i know the buffer cache and page cache was unified from Linux kernel version 2.4. So i wondered why fio with option direct=1 that didn’t bypass page cache as it should? > > I didn’t see page cache increasing when using dd with oflag=direct to copy or write file to disk. > > Please correct me if i am wrong. > > Thanks a lot in advance. > > Regards, > Son > > -- > To unsubscribe from this list: send the line "unsubscribe fio" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe fio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
