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| author | Matthew Pickering <matthewtpickering@gmail.com> | 2020-11-18 11:36:07 +0000 |
|---|---|---|
| committer | Matthew Pickering <matthewtpickering@gmail.com> | 2021-03-03 19:09:34 +0000 |
| commit | 4b297979d25740d31241a9000e36068db112545a (patch) | |
| tree | e2e40fa7922fb4a91125c73fcbae04e7a6a66f73 /docs/users_guide/profiling.rst | |
| parent | 8402ea951b31e01a925ca691747d1757eaf31fcc (diff) | |
| download | haskell-4b297979d25740d31241a9000e36068db112545a.tar.gz | |
Add -finfo-table-map which maps info tables to source positions
This new flag embeds a lookup table from the address of an info table
to information about that info table.
The main interface for consulting the map is the `lookupIPE` C function
> InfoProvEnt * lookupIPE(StgInfoTable *info)
The `InfoProvEnt` has the following structure:
> typedef struct InfoProv_{
> char * table_name;
> char * closure_desc;
> char * ty_desc;
> char * label;
> char * module;
> char * srcloc;
> } InfoProv;
>
> typedef struct InfoProvEnt_ {
> StgInfoTable * info;
> InfoProv prov;
> struct InfoProvEnt_ *link;
> } InfoProvEnt;
The source positions are approximated in a similar way to the source
positions for DWARF debugging information. They are only approximate but
in our experience provide a good enough hint about where the problem
might be. It is therefore recommended to use this flag in conjunction
with `-g<n>` for more accurate locations.
The lookup table is also emitted into the eventlog when it is available
as it is intended to be used with the `-hi` profiling mode.
Using this flag will significantly increase the size of the resulting
object file but only by a factor of 2-3x in our experience.
Diffstat (limited to 'docs/users_guide/profiling.rst')
| -rw-r--r-- | docs/users_guide/profiling.rst | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/docs/users_guide/profiling.rst b/docs/users_guide/profiling.rst index 75569f6409..097d7d0de3 100644 --- a/docs/users_guide/profiling.rst +++ b/docs/users_guide/profiling.rst @@ -802,8 +802,9 @@ following RTS options select which break-down to use: .. rts-flag:: -hi - Break down the graph by the address of the info table of a closure. This - profiling mode is intended to be used with :ghc-flag:`-finfo-table-map`. + Break down the graph by the address of the info table of a closure. For this + to produce useful output the program must have been compiled with + :ghc-flag:`-finfo-table-map`. .. rts-flag:: -l :noindex: |