2008/1/18, Miklos Szeredi <[EMAIL PROTECTED]>: > > 4. Performance test was done using the program available from the > > following link: > > > > http://bugzilla.kernel.org/attachment.cgi?id=14493 > > > > Result: the impact of the changes was negligible for files of a few > > hundred megabytes. > > Could you also test with ext4 and post some numbers? Afaik, ext4 uses > nanosecond timestamps, so the time updating code would be exercised > more during the page faults. > > What about performance impact on msync(MS_ASYNC)? Could you please do > some measurment of that as well?
Did a quick test on an ext4 partition. This is how it looks like: debian:~/miklos# ./miklos_test /mnt/file begin 1200662360 1200662360 1200662353 write 1200662361 1200662361 1200662353 mmap 1200662361 1200662361 1200662362 b 1200662363 1200662363 1200662362 msync b 1200662363 1200662363 1200662362 c 1200662365 1200662365 1200662362 msync c 1200662365 1200662365 1200662362 d 1200662367 1200662367 1200662362 munmap 1200662367 1200662367 1200662362 close 1200662367 1200662367 1200662362 sync 1200662367 1200662367 1200662362 debian:~/miklos# mount | grep /mnt /root/image.ext4 on /mnt type ext4dev (rw,loop=/dev/loop0) > What about performance impact on msync(MS_ASYNC)? Could you please do > some measurment of that as well? Following are the results of the measurements. Here are the relevant portions of the test program: >>> #define FILE_SIZE (1024 * 1024 * 512) p = mmap(0, FILE_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); /* Bring the pages in */ for (i = 0; i < FILE_SIZE; i += 4096) tmp = p[i]; /* Dirty the pages */ for (i = 0; i < FILE_SIZE; i += 4096) p[i] = i; /* How long did we spend in msync(MS_ASYNC)? */ gettimeofday(&tv_start, NULL); msync(p, FILE_SIZE, MS_ASYNC); gettimeofday(&tv_stop, NULL); <<< For reference tests, the following platforms were used: 1. HP-UX B.11.31, PA-RISC 8800 processor (800 MHz, 64 MB), Memory: 4 GB. 2. HP-UX B.11.31, 2 Intel(R) Itanium 2 9000 series processors (1.59 GHz, 18 MB), Memory: 15.98 GB. 3. FreeBSD 6.2-RELEASE, Intel(R) Pentium(R) III CPU family 1400MHz, 2 CPUs. Memory: 4G. The tests of my solution were performed using the following platform: A KVM x86_64 guest OS, current Git kernel. Host system: Intel(R) Core(TM)2 Duo CPU T7300 @ 2.00GHz. Further referred to as "the first case". The following tables give the time difference between the two calls to gettimeofday(). The test program was run three times in a raw with a delay of one second between consecutive runs. On Linux systems, the following commands were issued prior to running the tests: echo 80 >/proc/sys/vm/dirty_ratio echo 80 >/proc/sys/vm/dirty_background_ratio echo 30000 >/proc/sys/vm/dirty_expire_centisecs sync Table 1. Reference platforms. ------------------------------------------------------------ | | HP-UX/PA-RISC | HP-UX/Itanium | FreeBSD | ------------------------------------------------------------ | First run | 263405 usec | 202283 usec | 90 SECONDS | ------------------------------------------------------------ | Second run | 262253 usec | 172837 usec | 90 SECONDS | ------------------------------------------------------------ | Third run | 238465 usec | 238465 usec | 90 SECONDS | ------------------------------------------------------------ It looks like FreeBSD is a clear outsider here. Note that FreeBSD showed an almost liner depencence of the time spent in the msync(MS_ASYNC) call on the file size. Table 2. The Qemu system. File size is 512M. --------------------------------------------------- | | Before the patch | After the patch | --------------------------------------------------- | First run | 35 usec | 5852 usec | --------------------------------------------------- | Second run | 35 usec | 4444 usec | --------------------------------------------------- | Third run | 35 usec | 6330 usec | --------------------------------------------------- I think that the data above prove the viability of the solution I presented. Also, I guess that this bug fix is most probably ready for getting upstream. Please apply the sixth version of my solution. > > Thanks, > Miklos > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/