Using an SSD "disk" for /
Oliver Fromme
olli at lurza.secnetix.de
Fri Nov 5 07:57:10 UTC 2010
Oliver Fromme wrote:
> With /usr/src and /usr/obj both on the same SATA-300 HDD,
> a buildworld takes 10 minutes and 13 seconds.
>
> With /usr/src and /usr/obj on separate memory disks,
> a buildworld takes 10 minutes and 4 seconds.
>
> This is stable/8 with empty /etc/src.conf, i.e. a complete
> buildworld. The machine is an AMD Phenom II X6 (hexacore).
I think I should give some more information about the
system that I used for the test.
The HDD is accessed via ahci(4) and ada(4) with NCQ.
This might make a small difference, though I haven't
benchmarked it. src and obj are mounted with noatime.
In the memory disk case, src was even mounted read-only,
and obj was mounted async.
I made sure that there was no swapping / page-out
activity during the memory disk test, so all the data
really stayed in RAM (which should be even faster
than an SSD, I assume). The system was otherwise idle,
gstat(8) basically showed nothing on ada0 during the
memory disk test.
The following sysctl tunings are in effect:
vfs.hirunningspace=8388608
vfs.lorunningspace=1048576
vfs.read_max=32
vfs.ufs.dirhash_maxmem=33554432
kern.sched.preempt_thresh=220
(I've got more things in /etc/sysctl.conf, but the rest
shouldn't affect file system performance or buildworld,
I think.)
The kernel is running with HZ=300 (unfortunately HZ isn't
dynamic in FreeBSD, so I'm using 300 as a trade-off).
AUDIT and MAC are disabled.
Best regards
Oliver
--
Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing b. M.
Handelsregister: Registergericht Muenchen, HRA 74606, Geschäftsfuehrung:
secnetix Verwaltungsgesellsch. mbH, Handelsregister: Registergericht Mün-
chen, HRB 125758, Geschäftsführer: Maik Bachmann, Olaf Erb, Ralf Gebhart
FreeBSD-Dienstleistungen, -Produkte und mehr: http://www.secnetix.de/bsd
"When your hammer is C++, everything begins to look like a thumb."
-- Steve Haflich, in comp.lang.c++
More information about the freebsd-fs
mailing list