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From: Thomas Monjalon <thomas@monjalon.net>
To: Andrzej Ostruszka <aostruszka@marvell.com>
Cc: dev@dpdk.org, Aaron Conole <aconole@redhat.com>,
	Michael Santana <msantana@redhat.com>,
	John McNamara <john.mcnamara@intel.com>,
	Marko Kovacevic <marko.kovacevic@intel.com>,
	David Hunt <david.hunt@intel.com>,
	Bruce Richardson <bruce.richardson@intel.com>,
	Vladimir Medvedkin <vladimir.medvedkin@intel.com>,
	Robert Sanford <rsanford@akamai.com>,
	Erik Gabriel Carrillo <erik.g.carrillo@intel.com>,
	mattias.ronnblom@ericsson.com, stephen@networkplumber.org,
	john.mcnamara@intel.com, marko.kovacevic@intel.com
Subject: Re: [dpdk-dev] [PATCH v4 01/10] build: add an option to enable LTO build
Date: Sun, 27 Oct 2019 12:47:44 +0100
Message-ID: <12578231.CQkhPFEoQU@xps> (raw)
In-Reply-To: <20191022115412.8837-2-aostruszka@marvell.com>

Adding John and Marko for doc review.

22/10/2019 13:54, Andrzej Ostruszka:
> --- /dev/null
> +++ b/doc/guides/prog_guide/lto.rst

This new file is not included in the prog guide index.

> @@ -0,0 +1,36 @@

You are missing the mandatory SPDX and Copyright header.

> +Link Time Optimization
> +======================
> +
> +The DPDK framework supports compilation with link time optimization

Instead of "The DPDK framework", I prefer just "DPDK".

> +turned on.  This depends obviously on the capabilities of the compiler

Not sure what you are talking about.
If it is about fat objects, it is not obvious.

> +to do "whole program" optimization at link time and is available only
> +for compilers that support that feature (gcc and icc).  To be more

Please start a new sentence at the beginning of a line in the RsT file.
It is easier to review and update.

> +specific compiler have to support creation of ELF objects containing

A comma is missing after "specific".

> +both normal code and internal representation (fat-lto-objects).  This is
> +required since during build some code is generated by parsing produced
> +ELF objects (pmdinfogen).
> +
> +The amount of performance gain that one can get from LTO depends on the
> +compiler and the code that is being compiled.  However LTO is also
> +useful for additional code analysis done by the compiler.  In particular
> +due to interprocedural analysis compiler can produce additional warnings
> +about variables that might be used uninitialized.  Some of these
> +warnings might be "false positives" though and you might need to
> +explicitly initialize variable in order to silence the compiler.

Any word about build speed degradation?

> +
> +Link time optimization can be enabled for whole DPDK framework by
> +setting:
> +
> +.. code-block:: console
> +    CONFIG_ENABLE_LTO=y
> +
> +in config file for the case of make based build and by:
> +
> +.. code-block:: console
> +    meson build -Db_lto=true
> +    ninja -C build

No need to add the ninja step here.

> +for the case of meson based build.

Better to describe the case (make or meson) before the code-block.

> +Please note that turning LTO on causes considerable extension of
> +compilation time.

"compilation time" is not accurate.
When referring to compilation + linking, it is better to use the words
"build time".


> --- a/doc/guides/rel_notes/release_19_11.rst
> +++ b/doc/guides/rel_notes/release_19_11.rst
> @@ -56,6 +56,14 @@ New Features
>       Also, make sure to start the actual text at the margin.
>       =========================================================
>  
> +**Added build support for Link Time Optimization.**
> +
> + LTO is an optimization technique used by the compiler to perform whole
> + program analysis and optimization at link time.  In order to do that
> + compilers store their internal representation of the source code that
> + the linker uses at the final stage of compilation process.
> +
> + See :doc:`../prog_guide/lto` for more information:

Please rebase and add a blank line when adding a paragraph.

>  
>  Removed Items
>  -------------

> --- a/lib/librte_distributor/rte_distributor.c
> +++ b/lib/librte_distributor/rte_distributor.c
> -void
> +void __vsym

I replied in v2 about this change. Better to not talk about it here.


I wanted to merge this series in 19.11-rc1 but I think it is better
to move its merge in 19.11-rc2.
Thanks for the work.



  parent reply index

Thread overview: 110+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-17  7:57 [dpdk-dev] [PATCH v2 00/10] Add an option to use LTO for DPDK build Andrzej Ostruszka
2019-09-17  7:57 ` [dpdk-dev] [PATCH v2 01/10] build: add an option to enable LTO build Andrzej Ostruszka
2019-09-18 10:36   ` Bruce Richardson
2019-09-18 13:32   ` Ray Kinsella
2019-09-19 12:35     ` Andrzej Ostruszka
2019-09-19 13:28       ` Ray Kinsella
2019-09-19 15:16         ` Bruce Richardson
2019-09-20  7:38           ` Ray Kinsella
2019-09-23  7:23             ` Thomas Monjalon
2019-09-23  9:36               ` Ray Kinsella
2019-09-23 10:16                 ` Mattias Rönnblom
2019-09-23 12:03               ` Andrzej Ostruszka
2019-09-23 12:06                 ` Bruce Richardson
2019-09-23 13:02                   ` Andrzej Ostruszka
2019-09-23 16:13                     ` Bruce Richardson
2019-09-24  6:46                       ` Andrzej Ostruszka
2019-09-24 10:25                         ` Bruce Richardson
2019-09-24 11:52                           ` Andrzej Ostruszka
2019-09-24 12:11                             ` Bruce Richardson
2019-09-24 12:59                           ` Neil Horman
2019-09-24 16:01                             ` Ray Kinsella
2019-09-26 15:32                             ` Andrzej Ostruszka
2019-09-27 19:55                               ` Bruce Richardson
2019-09-23 12:16                 ` Ray Kinsella
2019-10-27 11:31     ` Thomas Monjalon
2019-10-28  8:36       ` Andrzej Ostruszka
2019-10-28  9:07         ` Thomas Monjalon
2019-10-28 12:12         ` Andrzej Ostruszka
2019-10-28 17:16           ` Thomas Monjalon
2019-09-17  7:57 ` [dpdk-dev] [PATCH v2 02/10] eventdev: fix possible use of uninitialized var Andrzej Ostruszka
2019-10-12 13:35   ` Jerin Jacob
2019-09-17  7:57 ` [dpdk-dev] [PATCH v2 03/10] app/eventdev: fix maybe-uninitialized warnings for LTO build Andrzej Ostruszka
2019-10-12 13:52   ` Jerin Jacob
2019-09-17  7:57 ` [dpdk-dev] [PATCH v2 04/10] event/octeontx2: " Andrzej Ostruszka
2019-09-17  7:57 ` [dpdk-dev] [PATCH v2 05/10] app/test: " Andrzej Ostruszka
2019-09-17  7:57 ` [dpdk-dev] [PATCH v2 06/10] net/dpaa2: fix possible use of uninitialized vars Andrzej Ostruszka
2019-09-17  7:57 ` [dpdk-dev] [PATCH v2 07/10] net/e1000: fix maybe-uninitialized warnings for LTO build Andrzej Ostruszka
2019-09-17  7:57 ` [dpdk-dev] [PATCH v2 08/10] net/i40e: " Andrzej Ostruszka
2019-09-17  7:57 ` [dpdk-dev] [PATCH v2 09/10] net/ifc: " Andrzej Ostruszka
2019-09-17  7:57 ` [dpdk-dev] [PATCH v2 10/10] net/qede: " Andrzej Ostruszka
     [not found] ` <20191021105707.25691-1-aostruszka@marvell.com>
     [not found]   ` <20191021105707.25691-2-aostruszka@marvell.com>
2019-10-21 12:59     ` [dpdk-dev] [PATCH v3 01/10] build: add an option to enable " Bruce Richardson
2019-10-22  8:53       ` Andrzej Ostruszka
2019-10-22 11:54 ` [dpdk-dev] [PATCH v4 00/10] Add an option to use LTO for DPDK build Andrzej Ostruszka
2019-10-22 11:54   ` [dpdk-dev] [PATCH v4 01/10] build: add an option to enable LTO build Andrzej Ostruszka
2019-10-22 12:45     ` Bruce Richardson
2019-10-27 11:47     ` Thomas Monjalon [this message]
2019-10-28 10:47       ` Andrzej Ostruszka
2019-10-28 11:03         ` Thomas Monjalon
2019-10-22 11:54   ` [dpdk-dev] [PATCH v4 02/10] eventdev: fix possible use of uninitialized var Andrzej Ostruszka
2019-10-22 11:54   ` [dpdk-dev] [PATCH v4 03/10] app/eventdev: clean LTO build warnings (maybe-uninitialized) Andrzej Ostruszka
2019-10-22 11:54   ` [dpdk-dev] [PATCH v4 04/10] event/octeontx2: " Andrzej Ostruszka
2019-10-22 11:54   ` [dpdk-dev] [PATCH v4 05/10] app/test: " Andrzej Ostruszka
2019-10-22 11:54   ` [dpdk-dev] [PATCH v4 06/10] net/dpaa2: fix possible use of uninitialized vars Andrzej Ostruszka
2019-10-22 11:54   ` [dpdk-dev] [PATCH v4 07/10] net/e1000: clean LTO build warnings (maybe-uninitialized) Andrzej Ostruszka
2019-10-22 11:54   ` [dpdk-dev] [PATCH v4 08/10] net/i40e: " Andrzej Ostruszka
2019-10-22 11:54   ` [dpdk-dev] [PATCH v4 09/10] net/ifc: " Andrzej Ostruszka
2019-10-22 11:54   ` [dpdk-dev] [PATCH v4 10/10] net/qede: " Andrzej Ostruszka
2019-10-22 12:48   ` [dpdk-dev] [PATCH v4 00/10] Add an option to use LTO for DPDK build Bruce Richardson
2019-10-22 13:03     ` Andrzej Ostruszka
2019-10-28 14:21   ` [dpdk-dev] [PATCH v5 00/11] " Andrzej Ostruszka
2019-10-28 14:21     ` [dpdk-dev] [PATCH v5 01/11] build: annotate versioned symbols with __vsym macro Andrzej Ostruszka
2019-10-29 10:49       ` Neil Horman
2019-10-28 14:21     ` [dpdk-dev] [PATCH v5 02/11] build: add an option to enable LTO build Andrzej Ostruszka
2019-10-28 14:21     ` [dpdk-dev] [PATCH v5 03/11] eventdev: fix possible use of uninitialized var Andrzej Ostruszka
2019-10-28 14:21     ` [dpdk-dev] [PATCH v5 04/11] app/eventdev: clean LTO build warnings (maybe-uninitialized) Andrzej Ostruszka
2019-10-28 14:21     ` [dpdk-dev] [PATCH v5 05/11] event/octeontx2: " Andrzej Ostruszka
2019-10-28 14:21     ` [dpdk-dev] [PATCH v5 06/11] app/test: " Andrzej Ostruszka
2019-10-28 14:21     ` [dpdk-dev] [PATCH v5 07/11] net/dpaa2: fix possible use of uninitialized vars Andrzej Ostruszka
2019-10-28 14:21     ` [dpdk-dev] [PATCH v5 08/11] net/e1000: clean LTO build warnings (maybe-uninitialized) Andrzej Ostruszka
2019-10-28 14:21     ` [dpdk-dev] [PATCH v5 09/11] net/i40e: " Andrzej Ostruszka
2019-10-28 14:21     ` [dpdk-dev] [PATCH v5 10/11] net/ifc: " Andrzej Ostruszka
2019-10-28 14:21     ` [dpdk-dev] [PATCH v5 11/11] net/qede: " Andrzej Ostruszka
2019-10-29 14:12     ` [dpdk-dev] [PATCH v6 00/12] Add an option to use LTO for DPDK build Andrzej Ostruszka
2019-10-29 14:12       ` [dpdk-dev] [PATCH v6 01/12] doc: fix description of versioning macros Andrzej Ostruszka
2019-10-29 14:12       ` [dpdk-dev] [PATCH v6 02/12] build: annotate versioned symbols with __vsym macro Andrzej Ostruszka
2019-10-29 14:12       ` [dpdk-dev] [PATCH v6 03/12] build: add an option to enable LTO build Andrzej Ostruszka
2019-10-29 14:12       ` [dpdk-dev] [PATCH v6 04/12] eventdev: fix possible use of uninitialized var Andrzej Ostruszka
2019-10-29 14:12       ` [dpdk-dev] [PATCH v6 05/12] app/eventdev: clean LTO build warnings (maybe-uninitialized) Andrzej Ostruszka
2019-10-29 14:12       ` [dpdk-dev] [PATCH v6 06/12] event/octeontx2: " Andrzej Ostruszka
2019-10-29 14:12       ` [dpdk-dev] [PATCH v6 07/12] app/test: " Andrzej Ostruszka
2019-11-01 17:15         ` Wang, Yipeng1
2019-11-04 13:48           ` Andrzej Ostruszka
2019-11-07 17:48             ` Wang, Yipeng1
2019-10-29 14:12       ` [dpdk-dev] [PATCH v6 08/12] net/dpaa2: fix possible use of uninitialized vars Andrzej Ostruszka
2019-11-04 11:46         ` Hemant Agrawal
2019-11-04 14:33           ` Andrzej Ostruszka
2019-10-29 14:12       ` [dpdk-dev] [PATCH v6 09/12] net/e1000: clean LTO build warnings (maybe-uninitialized) Andrzej Ostruszka
2019-10-29 14:12       ` [dpdk-dev] [PATCH v6 10/12] net/i40e: " Andrzej Ostruszka
2019-11-01  2:05         ` Xing, Beilei
2019-11-04 14:06           ` Andrzej Ostruszka
2019-10-29 14:12       ` [dpdk-dev] [PATCH v6 11/12] net/ifc: " Andrzej Ostruszka
2019-10-29 14:12       ` [dpdk-dev] [PATCH v6 12/12] net/qede: " Andrzej Ostruszka
2019-10-30  9:09       ` [dpdk-dev] [PATCH v6 00/12] Add an option to use LTO for DPDK build Andrzej Ostruszka
2019-10-30 14:23         ` Aaron Conole
2019-11-07 15:03       ` [dpdk-dev] [PATCH v7 " Andrzej Ostruszka
2019-11-07 15:03         ` [dpdk-dev] [PATCH v7 01/12] doc: fix description of versioning macros Andrzej Ostruszka
2019-11-07 15:03         ` [dpdk-dev] [PATCH v7 02/12] build: annotate versioned symbols with __vsym macro Andrzej Ostruszka
2019-11-07 15:03         ` [dpdk-dev] [PATCH v7 03/12] build: add an option to enable LTO build Andrzej Ostruszka
2019-11-07 15:03         ` [dpdk-dev] [PATCH v7 04/12] eventdev: fix possible use of uninitialized var Andrzej Ostruszka
2019-11-07 15:03         ` [dpdk-dev] [PATCH v7 05/12] app/eventdev: clean LTO build warnings (maybe-uninitialized) Andrzej Ostruszka
2019-11-07 15:03         ` [dpdk-dev] [PATCH v7 06/12] event/octeontx2: " Andrzej Ostruszka
2019-11-07 15:03         ` [dpdk-dev] [PATCH v7 07/12] app/test: " Andrzej Ostruszka
2019-11-07 17:53           ` Wang, Yipeng1
2019-11-07 15:03         ` [dpdk-dev] [PATCH v7 08/12] net/dpaa2: fix possible use of uninitialized vars Andrzej Ostruszka
2019-11-07 15:03         ` [dpdk-dev] [PATCH v7 09/12] net/e1000: clean LTO build warnings (maybe-uninitialized) Andrzej Ostruszka
2019-11-07 15:03         ` [dpdk-dev] [PATCH v7 10/12] net/i40e: " Andrzej Ostruszka
2019-11-07 15:03         ` [dpdk-dev] [PATCH v7 11/12] net/ifc: " Andrzej Ostruszka
2019-11-07 15:03         ` [dpdk-dev] [PATCH v7 12/12] net/qede: " Andrzej Ostruszka
2019-11-08 14:24         ` [dpdk-dev] [PATCH v7 00/12] Add an option to use LTO for DPDK build Thomas Monjalon
2019-11-01 21:33 ` [dpdk-dev] [PATCH v2 00/10] " Stephen Hemminger

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