Gentoo Archives: gentoo-user

From: Bastian Balthazar Bux <BastianBalthazarBux@×××××××××.it>
To: gentoo-user@l.g.o
Subject: Re: [gentoo-user] kernel tuning
Date: Mon, 03 Oct 2005 20:51:05
Message-Id: 43419892.5020101@pnpitalia.it
In Reply to: Re: [gentoo-user] kernel tuning by "Brett I. Holcomb"
1 Brett I. Holcomb wrote:
2 > Out of curiosity and so I can learn. Why did you suggest CONFIG_HZ be
3 > set to 100 (IIRC default is 250) and also what exactly is it supposed to
4 > do for you. We did not have it before.
5 >
6
7 In the past was fixed to 100Hz, then to 1000 appeared, now there is a
8 third option for 250, the current default and a good compromise.
9
10 An home system become more responsive with a higher frequency.
11
12 cpu and interrupt timings become lower with a lower frequency, so it's
13 better for a server system. Expecially a multi processor one.
14
15
16
17 > Also what about CONFIG_PREMPT being none? The help mentions it is for
18 > low latency.
19
20 >> CONFIG_HZ=100
21 >> CONFIG_PREEMPT_NONE=y
22 >> IOSCHED_AS || IOSCHED_DEADLINE || IOSCHED_CFQ
23 >>
24
25 Preemption permit to interrupt kernel processes, providing a still more
26 responsive kernel. Good if you're hering music, playing videos and such
27 but not very interesting for a server.
28
29 The third option is the "scheduler" (IOSCHED_*) how the kernel access
30 the disk. this has been discussed in great detail over the net.
31 Quoting the kernel help here, since it's short and explanatory.
32
33 --------- quote ---------
34 CONFIG_IOSCHED_AS:
35
36 The anticipatory I/O scheduler is the default disk scheduler. It is
37 generally a good choice for most environments, but is quite large and
38 complex when compared to the deadline I/O scheduler, it can also be
39 slower in some cases especially some database loads.
40
41 Symbol: IOSCHED_AS [=y]
42 Prompt: Anticipatory I/O scheduler
43 Defined at drivers/block/Kconfig.iosched:14
44 Location:
45 -> Device Drivers
46 -> Block devices
47 -> IO Schedulers
48 --------- quote ---------
49
50 --
51 gentoo-user@g.o mailing list

Replies

Subject Author
Re: [gentoo-user] kernel tuning "Brett I. Holcomb" <brettholcomb@×××××××××.net>