2012/5/27 Adam Borowski wrote: > First, you're benchmarking the speed of process creation, not of file > operations. Starting up seq or mv takes ages compared to an in-memory > file write.
They may be slower than in-memory operations, but they're definitely faster than fsync(). So if there was fsync() there would have been a noticeable difference in time. But there were no difference. So there were no fsync(). And my HDD was not blinking during that test as well. :) > Then, pray tell, where exactly do your tests include a fsync()? You're > using a 0-byte file (ie, without an actual data block). And even if you > added some actual data, your test would do a writeout exactly once -- > after the first rename, all data blocks would be already on the disk. Well, you said that rename calls fsync, I checked that. :) You're saying I should have written something there before renaming? Let's check it too: $ cd /path/to/empty/ext3/dir/ $ time for i in `seq 10000`; do echo 12345 > 1; mv 1 2; rm -f 2; done real 0m20.125s user 0m4.283s sys 0m14.066s $ cd /path/to/empty/tmpfs/dir/ $ time for i in `seq 10000`; do echo 12345 > 1; mv 1 2; rm -f 2; done real 0m20.005s user 0m4.076s sys 0m13.088s Still no difference. Both tests took 19-20 seconds And again there were no HDD blinking during the test. :) Fsync() is a myth? > Please fix your tests, then. Because, yes, tmpfs doesn't speed up fork(), > exec(), setlocale(), getopt() and such. True. These tests are useless as a benchmarks. They only prove that there's no fsync(), nothing else. I could write that in C, but it's pointless. Because there're still no *real* applications doing that! And if there're no applications doing heavy rename() in /tmp then what are we testing this for? Why are we moving *default* /tmp to tmpfs? To make these useless tests faster? Where's the real application becoming better after all? -- Serge -- To UNSUBSCRIBE, email to debian-devel-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/caovenep5qzb-rbwnybrewf2z7b99njmkebmk8z0s4omo6q4...@mail.gmail.com
