Gentoo Archives: gentoo-dev

From: William Kenworthy <billk@×××××××××.au>
To: frlinux@g.o
Cc: gentoo-dev ML <gentoo-dev@g.o>
Subject: Re: [gentoo-dev] "Distro Day (Measuring the benefits of the Gentoo approach)"
Date: Wed, 13 Aug 2003 22:57:31
Message-Id: 1060814942.27241.148.camel@rattus.Localdomain
In Reply to: Re: [gentoo-dev] "Distro Day (Measuring the benefits of the Gentoo approach)" by FRLinux
1 I posted this to the gentoo-user list by mistake last night (it was
2 after midnight and ...) - wondered why I didnt get too many
3 flames/replies!
4
5 Apologies to those who get two copies, but it was originally meant to go
6 with this thread to stop the mis-information:
7
8 ______posted to gentoo-user_______________________
9
10 I'll stick my hand up and say I was the person who installed gentoo for
11 this test. For those who made the previous posts (mostly crap, and who
12 dont seem to have read the article very well - though it could have been
13 more informative), perhaps a few facts may help:
14
15 1. was fully bootstrapped and compiled as stage 1/2/3 on the machine -
16 not a binary install
17 2. gentoo-sources 2.4.20 was used - Mandrake came with a newer kernel
18 than gentoo's reccomended one (still does), debian was a dogs breakfast
19 because stable is so old. We actually tried to put the gentoo kernel on
20 mandrake/debian when tracking down the ide cable prob, but got too hard
21 - not the way some posts tried to imply)
22 3. optimisations were EXACTLY as recommended by both the make.conf
23 entries, which were supported by the cflags from the forum for this cpu:
24 a 2G celery (P4 based core) I am not sure now, but I believe I ran
25 prelink as well (to match mandrake) - need to find and check the notes.
26 4. Gnumerics problems have been identified and come down to the
27 particular version - is fixed in the upcoming stable release even before
28 this was found, but the project was unaware that what they believed was
29 a slightly slower mod in this version, could be so bad on particular
30 data sets - i.e., 30 odd mins in 1.0.13, but is less that 30s on 1.0.19
31 on my laptop
32
33 There seems to be quite a few myths about this test and people upset
34 that months were not spent tuning gentoo and every effort made to
35 cripple the competition! (one person even suggested the faulty ide cable
36 should have been left in the debian box, as that was the way it was
37 delivered!) Read the article, and if you need extra information to
38 reproduce it, email me or or the author (Indy). It is reproducable - if
39 you can obtain the same hardware - I would be very interested if someone
40 has this and the time to really go into the why these results occurred
41 in more detail than I had the chance to.
42
43 and why was this the result? Daniel Robbins suggested on this list that
44 gentoo-sources may be the problem, but tests on another machine (we had
45 the trial machines for only a couple of days, all of which time was used
46 to build gentoo right up until I ctrl-c'd the OO build so we could do
47 the tests before handing the hardware back) showed that turning off
48 pre-empt and low-latency had zero effect, but changing to an open-mosix
49 kernel 2.4.20 was ~10% slower (no thread export). It seemed to come
50 down to the fact we used -O3 instead of -O2 (think spider might have
51 suggested this ?)- in effect over-optimised, and we didnt have a chance
52 to correct. From my perspective, most of the "he should have used ...
53 may actually have made performance even worse! And besides the time
54 issue, these were supposedly the safe, reccomended flags so we went with
55 them. Please note that even Mandrake made only a slight gain on debian,
56 so 386.586/686 does not make a lot of difference in real world tasks
57 (the original aim of the tests) - the tests did tasks that particular
58 people used linux for in their day-to-day work - no special tests, so no
59 special bias. Yes, I could choose tests that make gentoo shine, or
60 debian, or windowsXP. But I dont do those tests every day, whilst that
61 spreadsheet was/is used as part of my normal work. And its the same
62 with the other tests.
63
64 So how many gentoo systems out there have every possible optimisation in
65 the book, and are actually running slower than ideal? This is a real
66 problem, and I will be interested in how the cflags projects around
67 handle this, as most seem to aim at setting the maximum possible flags:
68 not actually tune the system for the ones that work best/most stably. A
69 live benchmark test might be more appropriate.
70
71 Most posts on irc and lists have settled down to "he doesnt know what
72 he's doing" (I do), or the tests were unfair to gentoo (they werent, but
73 then the same criteria were met by all 3 systems, but with some question
74 marks over debian because of its mix - some packages had to be compiled
75 locally, not binary) - but the thrust of the article was not that gentoo
76 was a dud, but that this was the result within the criteria and time we
77 were given, not what we expected, so we need to find out why. Also note
78 that this was not intentionally a debian/mandrake/gentto distro test.
79
80 We may be getting a P4 hyperthreaded system to play with, but under
81 different rules, where I get to do a bit of tuning first. I have
82 already built the core system on another machine using gcc-3.2.3,
83 "-march=pentium4 -O3 -pipe -fomit-frame-pointer" I note that the
84 pentium4 warning still appears in make.conf, though I believe it no
85 longer applies to this gcc.
86
87 A while ago I emailed this list and asked for information on tests and
88 settings for HT P4's, without a reply. So again, has anyone done any
89 tests on a HT P4 and is willing to support the flags they chose as being
90 "the best"? In particular, does -ffast-math give a measurable gain?
91 Most of my machines have been built as scientific stations, so accuracy
92 is more important than ultimate speed, so this is one I have never
93 tested. I am not interested in the -O9 -max-everything kiddies who have
94 been so vocal, but reasoned choices.
95
96 If you want to flame, go ahead - but support your statements!
97
98 :)
99
100 BillK
101
102
103
104 On Thu, 2003-08-14 at 05:15, FRLinux wrote:
105 > On Wed, 2003-08-13 at 15:20, Philippe Lafoucrière wrote:
106 > > totally agree ! Btw, gnumeric speed is related to version apparently,
107 > > and they didn't use the official gentoo (patched) kernel ("The same
108 > > 2.4.21 source was copied to all machines"). This sux !!
109 >
110 > Well i don't think this sucks, keeping at least consistency on the
111 > kernel between the 3 distributions is a good idea. Now, that being said,
112 > they seriously fsck'd up the rest of the test and optimisations.
113 >
114 > I don't use specific gentoo kernels on my boxes, this is a personal
115 > choice made about a year ago and actually since 2.6, i don't use 2.4
116 > anymore on personal machines (my laptop and my workstation).
117 >
118 > Steph
119 --
120 William Kenworthy <billk@×××××××××.au>
121
122
123 --
124 gentoo-dev@g.o mailing list

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