Re: numbers don't lie ...


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On Tue, Sep 19, 2006 at 04:11:12PM +0400, Dmitry Morozovsky wrote:
On Thu, 14 Sep 2006, Oliver Fromme wrote:
=20
OF> Because buildworld is I/O-bound on systems with sufficiently
OF> fast processors.
OF>=20
OF> Try putting the contents of /usr/src into a RAM disk and
OF> repeat the benchmark. The numbers might look a little
OF> different then. Of course, you should have sufficient RAM
OF> in the machines -- If they're going to swap to the disks,
OF> your benchmark won't be happy.
OF>=20
OF> I think putting /usr/obj onto a RAM disk is _not_ necessary
OF> because of soft-updates, so the processes shouldn't block
OF> on writes.
=20
My experiments show that if you have enough memory to host radmdrive for=
=20
/usr/src you'd better leave it for caching - there were no statistically
meaningful performance difference, at least on machines with 1G+ RAM.

Really? My measurements show the opposite (on a system with 16GB of
RAM).

Kris

here are a bunch of new numbers:
make: dell 2950
OS: Freebsd 6.2-PRERELEASE
cpu: XEON 3.20GHz dualcore * 2
memory: 4GB

no swap configured/used.

make buildworld -j 8:

src & obj real user system hyper
-------------------- --------- ---------- --------- -----
Dell PERC 5/i RAID 0 24m17.73s 1h4m31.49s 15m47.44s no
Dell PERC 5/i RAID 0 22m3.39s 1h38m46.84s 28m54.18s yes
iSCSI/netapp 26m49.98s 1h4m26.77s 16m12.89s no

src obj
--------------------
md Dell PERC 5/i 24m7.22s 1h4m44.94s 16m24.45 no

so, if numbers are to be believed:
1- hypert helps in the real time, but user and system are bigger.
allot of sweat for a very small gain.
2- src in memory made no change.
3- slow disc (iscsi) vs. very fast disk (PERC 5/i RAID 0) - about 1:3 speed,
produced
less than 10% gain in time.

danny


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