Gentoo Archives: gentoo-user

From: "Brett I. Holcomb" <brettholcomb@×××××××××.net>
To: gentoo-user@l.g.o
Subject: Re: [gentoo-user] kernel tuning
Date: Mon, 03 Oct 2005 20:56:32
Message-Id: Pine.LNX.4.63.0510031651120.11025@gandalf
In Reply to: Re: [gentoo-user] kernel tuning by Bastian Balthazar Bux
1 Thank you for the explanation. I missed that servers is what the OP is
2 really interested in. I'll look at the scheduler options again.
3
4
5 On Mon, 3 Oct 2005, Bastian Balthazar Bux wrote:
6
7 > Brett I. Holcomb wrote:
8 >> Out of curiosity and so I can learn. Why did you suggest CONFIG_HZ be
9 >> set to 100 (IIRC default is 250) and also what exactly is it supposed to
10 >> do for you. We did not have it before.
11 >>
12 >
13 > In the past was fixed to 100Hz, then to 1000 appeared, now there is a
14 > third option for 250, the current default and a good compromise.
15 >
16 > An home system become more responsive with a higher frequency.
17 >
18 > cpu and interrupt timings become lower with a lower frequency, so it's
19 > better for a server system. Expecially a multi processor one.
20 >
21 >
22 >
23 >> Also what about CONFIG_PREMPT being none? The help mentions it is for
24 >> low latency.
25 >
26 >>> CONFIG_HZ=100
27 >>> CONFIG_PREEMPT_NONE=y
28 >>> IOSCHED_AS || IOSCHED_DEADLINE || IOSCHED_CFQ
29 >>>
30 >
31 > Preemption permit to interrupt kernel processes, providing a still more
32 > responsive kernel. Good if you're hering music, playing videos and such
33 > but not very interesting for a server.
34 >
35 > The third option is the "scheduler" (IOSCHED_*) how the kernel access
36 > the disk. this has been discussed in great detail over the net.
37 > Quoting the kernel help here, since it's short and explanatory.
38 >
39 > --------- quote ---------
40 > CONFIG_IOSCHED_AS:
41 >
42 > The anticipatory I/O scheduler is the default disk scheduler. It is
43 > generally a good choice for most environments, but is quite large and
44 > complex when compared to the deadline I/O scheduler, it can also be
45 > slower in some cases especially some database loads.
46 >
47 > Symbol: IOSCHED_AS [=y]
48 > Prompt: Anticipatory I/O scheduler
49 > Defined at drivers/block/Kconfig.iosched:14
50 > Location:
51 > -> Device Drivers
52 > -> Block devices
53 > -> IO Schedulers
54 > --------- quote ---------
55 >
56 >
57
58 --
59
60 Brett I. Holcomb
61 brettholcomb@×××××××××××××.net
62 Registered Linux User #188143
63 Remove R777 to email
64 --
65 gentoo-user@g.o mailing list