On 04/08/19 17:46, Anatoli wrote:
That was with Samsung 960 EVO U.2 (PCIe) on i7-8550u with 32GB RAM.
OpenBSD read/write was around 220-240MB/s (with FS encryption), Linux
without FS cache about 2.6-2.8GB/s and with cache over 3.5GB/s.
I don't have a dmesg right now as I installed Gentoo on top and just
saved a printscreen of the tests (below), but I can reinstall OpenBSD
and make more specific tests if anybody is interested (I do am
interested in a reasonable OpenBSD performance, but I thought 12x
slower and no cache to improve things when I/O lags wasn't that strange).
If you can suggest some specific tests to analyze the cause (i.e.
filesystem, hardware issues, scheduling, etc.), please let me know.
*From:* Chris Cappuccio <ch...@nmedia.net>
*Sent:* Monday, April 08, 2019 16:28
*To:* Anatoli <m...@anatoli.ws>
*Cc:* Misc <misc@openbsd.org>
*Subject:* Re: 10GBit network performance on OpenBSD 6.4
Anatoli [m...@anatoli.ws] wrote:
I've seen extremely slow HDD performance in OpenBSD, like 12x slower
than on
Linux, also no filesystem cache, so depending on your HDD with scp
you may
be hitting the max throughput for the FS, not the network.
12x slower? That's insane. What are you talking about? USB HDD? USB
Flash?
SATA? Driver? You should submit a bug report with lots of details.
Chris
A quick test on a slow laptop running linux shows
dd if=/dev/zero of=a bs=64k count=20000
runs 1.3 GB/sec. The physical disk transfer rate is 80 MB/sec max.
Linux caches very aggressively.
What is the rated transfer rate of the SSD you're using to test?
SATA 3 wire speed is 6G/sec and realistically 500MB/sec raw rate
is near the top.
Anything over that is an artefact probably from a cache somewhere.
I suspect that if you tried to write more data than physical memory
can hold the transfer rate would slow to something under the
disk or channel rate.
OpenBSD saves a great deal less in its cache. This slows repetitive
accesses to large data sets a painful amount. That's a separate problem
which I'd like to look at but don't have the time to write the tools
to do it.
