Build flags - Revision history

FliegendeWurst: fix typos and similar

2024-12-30T17:18:32Z

fix typos and similar

← Older revision		Revision as of 17:18, 30 December 2024
Line 1:		Line 1:
	=== Building a package for a specific CPU ===		=== Building a package for a specific CPU ===
	By default, packages built for, say, x86_64 do not take advantage of the feature of more recent ~~cpus~~ so that the executables you compile also work on older ~~cpus~~ of the same architecture. This is essential because of the binary cache feature of ~~nix~~: if a package is compiled on ~~hydra by~~ a recent CPU, older systems using ~~hydra~~ may download software that they can't run.		By default, packages built for, say, x86_64 do not take advantage of the feature of more recent CPUs so that the executables you compile also work on older CPUs of the same architecture. This is essential because of the [[Binary Cache\|binary cache]] feature of Nix: if a package is compiled on [[Hydra]] for a recent CPU, older systems using Hydra may download software that they can't run.

	However, you can build some package or even all your system to take advantage of the specific model of your ~~cpu~~. Note that you will not be able to take advantage of the binary cache and thus build everything locally from scratch. The first step is to determine the <code>-march</code> and <code>-mtune</code> arguments that you want to pass to gcc. In the following we want to target a skylake ~~cpu~~ so <code>-march=skylake -mtune=skylake</code>.		However, you can build some package or even all your system to take advantage of the specific model of your CPU. Note that you will not be able to take advantage of the binary cache (except for FODs) and thus must build everything locally from scratch. The first step is to determine the <code>-march</code> and <code>-mtune</code> arguments that you want to pass to gcc. In the following we want to target a skylake CPU so we use <code>-march=skylake -mtune=skylake</code>.

	==== Building a single package ====		==== Building a single package ====
Line 28:		Line 28:
	==== Adapting a derivation to specific plaforms ====		==== Adapting a derivation to specific plaforms ====

	The technique above should pass the correct flags to gcc so that it uses the processor to its fullest. However, some build systems or configure scripts want to know whether to enable some processor-specific instructions, for example ~~sse~~. One way to do so is to inspect the <code>stdenv.hostPlatform.*Support</code> predicates~~: here~~ is an example from g2o:		The technique above should pass the correct flags to gcc so that it uses the processor to its fullest. However, some build systems or configure scripts want to know whether to enable some processor-specific instructions, for example SSE. One way to do so is to inspect the <code>stdenv.hostPlatform.*Support</code> predicates. Here is an example from g2o:
	<code>		<code>
	cmakeFlags = [ "-DDISABLE_SSE3=${ if stdenv.hostPlatform.sse3Support then "OFF" else "ON"}" ]		cmakeFlags = [ "-DDISABLE_SSE3=${ if stdenv.hostPlatform.sse3Support then "OFF" else "ON"}" ]
	</code>		</code>

Line 39:		Line 39:
	{ config, pkgs, lib, ... }:		{ config, pkgs, lib, ... }:
	{		{
	nixpkgs.hostPlatform = {		nixpkgs.hostPlatform = {
	gcc.arch = "skylake";		gcc.arch = "skylake";
	gcc.tune = "skylake";		gcc.tune = "skylake";
	system = "x86_64-linux";		system = "x86_64-linux";
	};		};
	}		}
	</nowiki>}}		</nowiki>}}

Klinger: Category:Development Category:nix

2024-04-24T20:25:03Z

Category:Development Category:nix

← Older revision		Revision as of 20:25, 24 April 2024
Line 64:		Line 64:
	pkgs.openssl		pkgs.openssl
	</syntaxhighlight>		</syntaxhighlight>

			[[Category:Development]]
			[[Category:nix]]

imported>Kquote03: updated to hostPlatform

2023-12-12T07:40:50Z

updated to hostPlatform

← Older revision		Revision as of 07:40, 12 December 2023
Line 39:		Line 39:
	{ config, pkgs, lib, ... }:		{ config, pkgs, lib, ... }:
	{		{
	nixpkgs.~~localSystem~~ = {		nixpkgs.hostPlatform = {
	gcc.arch = "skylake";		gcc.arch = "skylake";
	gcc.tune = "skylake";		gcc.tune = "skylake";

imported>Eopb: Fix path to configuration file

2023-07-12T19:51:28Z

Fix path to configuration file

← Older revision		Revision as of 19:51, 12 July 2023
Line 36:		Line 36:

	==== Building the whole system on NixOS ====		==== Building the whole system on NixOS ====
	{{file\|/etc/nixos/configuration/nix\|nix\|<nowiki>		{{file\|/etc/nixos/configuration.nix\|nix\|<nowiki>
	{ config, pkgs, lib, ... }:		{ config, pkgs, lib, ... }:
	{		{

imported>Srid: What are 'flags'?

2021-09-11T13:11:32Z

What are 'flags'?

← Older revision		Revision as of 13:11, 11 September 2021
Line 33:		Line 33:
	</code>		</code>

	Available flags are defined in [https://github.com/NixOS/nixpkgs/blob/master/lib/systems/architectures.nix lib/systems/architectures.nix].		Available [https://unix.stackexchange.com/questions/43539/what-do-the-flags-in-proc-cpuinfo-mean flags] are defined in [https://github.com/NixOS/nixpkgs/blob/master/lib/systems/architectures.nix lib/systems/architectures.nix].

	==== Building the whole system on NixOS ====		==== Building the whole system on NixOS ====

imported>Symphorien: mention stdenv.hostPlatform.*support

2021-08-29T11:44:46Z

mention stdenv.hostPlatform.*support

@@ Line 24: / Line 24: @@
 nix-build optimised_openssl.nix --option system-features gccarch-skylake
 </code>
 ==== Building the whole system on NixOS ====

imported>Appetrosyan: Moved to templates and fixed rendering.

2021-06-03T08:23:15Z

Moved to templates and fixed rendering.

← Older revision		Revision as of 08:23, 3 June 2021
Line 9:		Line 9:
	{{file\|optimised_openssl.nix\|nix\|<nowiki>		{{file\|optimised_openssl.nix\|nix\|<nowiki>
	let		let
	pkgs = import <nixpkgs> {		pkgs = </nowiki>import <nixpkgs> {<nowiki>
	localSystem = {		localSystem = {
	gcc.arch = "skylake";		gcc.arch = "skylake";
	gcc.tune = "skylake";		gcc.tune = "skylake";
	system = "x86_64-linux";		system = "x86_64-linux";
	};		</nowiki>};
	};		};
	in		in
	pkgs.openssl		pkgs.openssl
	~~</nowiki>~~}}		}}

	Then build the file:		Then build the file:

imported>Appetrosyan: Rewrote to use the file template

2021-06-03T08:13:59Z

Rewrote to use the file template

← Older revision		Revision as of 08:13, 3 June 2021
Line 7:		Line 7:
	You need to be a trusted user to override the local system feature.		You need to be a trusted user to override the local system feature.

	~~<code>~~optimised_openssl.nix<~~/code>~~		{{file\|optimised_openssl.nix\|nix\|<nowiki>
	~~<syntaxhighlight lang="nix"~~>
	let		let
	pkgs = import <nixpkgs> {		pkgs = import <nixpkgs> {
Line 19:		Line 18:
	in		in
	pkgs.openssl		pkgs.openssl
	</~~syntaxhighlight~~>		</nowiki>}}

	Then build the file:		Then build the file:
Line 27:		Line 26:

	==== Building the whole system on NixOS ====		==== Building the whole system on NixOS ====
	~~In <code>~~/etc/nixos/configuration/nix<~~/code>:~~		{{file\|/etc/nixos/configuration/nix\|nix\|<nowiki>
	~~<syntaxhighlight lang="nix"~~>
	{ config, pkgs, lib, ... }:		{ config, pkgs, lib, ... }:
	{		{
Line 37:		Line 35:
	};		};
	}		}
	</~~syntaxhighlight~~>		</nowiki>}}

imported>Lassulus at 20:23, 23 May 2021

2021-05-23T20:23:56Z

← Older revision		Revision as of 20:23, 23 May 2021
Line 5:		Line 5:

	==== Building a single package ====		==== Building a single package ====
	You need to be a ~~trested~~ user to override the local system feature.		You need to be a trusted user to override the local system feature.

	<code>optimised_openssl.nix</code>		<code>optimised_openssl.nix</code>

imported>Symphorien: Created page with "=== Building a package for a specific CPU === By default, packages built for, say, x86_64 do not take advantage of the feature of more recent cpus so that the executables you..."

2021-05-23T20:22:04Z

Created page with "=== Building a package for a specific CPU === By default, packages built for, say, x86_64 do not take advantage of the feature of more recent cpus so that the executables you..."

New page

=== Building a package for a specific CPU ===
By default, packages built for, say, x86_64 do not take advantage of the feature of more recent cpus so that the executables you compile also work on older cpus of the same architecture. This is essential because of the binary cache feature of nix: if a package is compiled on hydra by a recent CPU, older systems using hydra may download software that they can't run.

However, you can build some package or even all your system to take advantage of the specific model of your cpu. Note that you will not be able to take advantage of the binary cache and thus build everything locally from scratch. The first step is to determine the <code>-march</code> and <code>-mtune</code> arguments that you want to pass to gcc. In the following we want to target a skylake cpu so <code>-march=skylake -mtune=skylake</code>.

==== Building a single package ====
You need to be a trested user to override the local system feature.

<code>optimised_openssl.nix</code>
<syntaxhighlight lang="nix">
let
pkgs = import <nixpkgs> {
localSystem = {
gcc.arch = "skylake";
gcc.tune = "skylake";
system = "x86_64-linux";
};
};
in
pkgs.openssl
</syntaxhighlight>

Then build the file:
<code>
nix-build optimised_openssl.nix --option system-features gccarch-skylake
</code>

==== Building the whole system on NixOS ====
In <code>/etc/nixos/configuration/nix</code>:
<syntaxhighlight lang="nix">
{ config, pkgs, lib, ... }:
{
nixpkgs.localSystem = {
gcc.arch = "skylake";
gcc.tune = "skylake";
system = "x86_64-linux";
};
}
</syntaxhighlight>

=== Building an impure package with <code>-march=native</code> ===
{{Tip|You should always prefer the previous method. This one is impure.}}

To build an openssl specially tailored to the local CPU, build
<syntaxhighlight lang="nix">
let
pkgs = import <nixpkgs> {
overlays = [
(self: super: {
stdenv = super.impureUseNativeOptimizations super.stdenv;
})
];
};
in
pkgs.openssl
</syntaxhighlight>