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perf chapter: repair tikz figures #111

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May 7, 2024
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perf chapter: repair tikz figures #111

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32 changes: 17 additions & 15 deletions src/Measurement_Observation/Binary_Profiling/linux_perf.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -38,7 +38,8 @@ which is a constant that describes the kind of closure, for example, a
which the garbage collector requires to collect :term:`CAF`'s. Lastly, the info
table will hold the :term:`entry code` pointer for the heap object if one exists
[#]_ . For more see :ghcSource:`InfoTables.h
<rts/include/rts/storage/InfoTables.h>` for exact details and other variants.
<rts/include/rts/storage/InfoTables.h>` and :ghcSource:`Closures.h
<rts/include/rts/storage/Storage.h>` for exact details and variants.

Here is a depiction of the heap object layout without |TNTC| enabled. Code is
represented in orange and data in blue. Boxes which have a dashed outline change
Expand Down Expand Up @@ -83,14 +84,15 @@ depending on the type of heap object and build:
\draw[->, thick] (ip.south) |- (ecp.north west) node[midway] {};
\draw[->, thick] (ecp.east) |- (ec.west) node[midway] {};

Tables-next-to-code does two things: first it removes the entry code pointer
from the info table and second, it moves the entry code itself to the address
immediately after the info table and sets the info table pointer itself to the
address of the entry code. This setup allows the runtime system to save a
pointer indirection because the info table pointer now points to the entry code.
Thus, when jumping to the entry code, which is a common operation, the runtime
system saves a single indirection, but can still reference the fields of the
info table through a negative memory offset from the info table pointer.
Tables-next-to-code does two things: first it removes the entry code pointer and
places the type specific fields before the ``Closure Type``, and second, it
moves the entry code itself to the address immediately after the info table and
sets the info table pointer to the address of the entry code. This setup allows
the runtime system to save a pointer indirection because the info table pointer
now points to the entry code. Thus, when jumping to the entry code, which is a
common operation, the runtime system saves a single indirection, but can still
reference the fields of the info table through a negative memory offset from
the info table pointer.

Here is a depiction with |TNTC| enabled:

Expand All @@ -111,19 +113,19 @@ Here is a depiction with |TNTC| enabled:
(6,2.25)--node[rotate=0, yshift=7mm](header){Object Header} (14,2.25);

\node[below of=ip, draw,rectangle, thick, fill=blue!10,
minimum width=4cm, minimum height=2cm, xshift=5cm, yshift=-3cm] (layout) {Layout};
minimum width=4cm, minimum height=2cm, xshift=5cm, yshift=-5cm] (layout) {Layout};

\node[above of=layout, draw,rectangle, thick, dashed, fill=blue!10,
minimum width=4cm, minimum height=2cm, yshift=1cm] (other) {Type Specific
Fields};

\node[below of=layout, draw,rectangle, thick, fill=blue!10,
minimum width=4cm, minimum height=2cm, yshift=-1cm] (ct) {Closure Type};

\node[below of=ct, draw,rectangle, thick, fill=blue!10,
minimum width=4cm, minimum height=2cm, yshift=-1cm] (srt) {SRT Bitmap};

\node[below of=srt, draw,rectangle, thick, dashed, fill=blue!10,
minimum width=4cm, minimum height=2cm, yshift=-1cm] (other) {Type Specific
Fields};

\node[below of=other, draw,rectangle, thick, fill=orange!20,
\node[below of=srt, draw,rectangle, thick, fill=orange!20,
minimum width=4cm, minimum height=2cm, yshift=-1cm] (ec) {Entry Code};

\draw[->, thick] (ip.south) |- (ec.north west) node[midway] {};
Expand Down
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