On Wed, 29 Apr 2020 at 15:37, Sad Clouds <[email protected]> wrote: > > On Wed, 29 Apr 2020 09:17:54 +0100 > Chavdar Ivanov <[email protected]> wrote: > > > On my VirtualBox 6.1.6 guest running -current amd64 I get: > > > > $ time cat 80mb > /dev/null > > cat 80mb > /dev/null 0.00s user 0.02s system 98% cpu 0.021 total > > Yeah this test is not very useful, 80MiB is hardly anything and most of > it is probably going from/to file cache.
Sure; that was the OP was doing. More realistically time dd if=/dev/zero of=out bs=1m count=5000 5000+0 records in 5000+0 records out 5242880000 bytes transferred in 151.411 secs (34626810 bytes/sec) dd if=/dev/zero of=out bs=1m count=5000 0.01s user 31.65s system 20% cpu 2:31.42 total (didn't have 10GB free...) At the same time on a CentOS guest I get: ]$ time dd if=/dev/zero of=out bs=1M count=5000 conv=fdatasync 5000+0 records in 5000+0 records out 5242880000 bytes (5.2 GB) copied, 19.8532 s, 264 MB/s even if the NetBSD vm is backed by a M.2 SATA sdd, whereas the CentOS guest has its vd on a spinning disk. Read what you want. There have been many discussions regarding the caching and some specific optimizations under Linux, I recall. > > If you write around 10GiB > > dd if=/dev/zero of=out bs=1m count=10000 > > do you get similar I/O throughput on NetBSD and Linux guests? -- ----
