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documentation: Remove unnecessary images from requirements 

This commit removes a cutesy cartoon and also a diagram that can
just as easily be represented by text.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
hifive-unleashed-5.1
Paul E. McKenney 2016-03-15 11:03:36 -07:00
parent 514f1eb5f4
commit 11a65df573
4 changed files with 40 additions and 253 deletions
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Documentation/RCU/Design/Requirements/2013-08-is-it-dead.png
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Documentation/RCU/Design/Requirements/RCUApplicability.svg
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@ -1,237 +0,0 @@
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xmlns:svg="http://www.w3.org/2000/svg"
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<metadata
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<cc:Work
rdf:about="">
<dc:format>image/svg+xml</dc:format>
<dc:type
rdf:resource="http://purl.org/dc/dcmitype/StillImage" />
<dc:title />
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x="4050"
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<text
xml:space="preserve"
x="7200"
y="900"
font-style="normal"
font-weight="normal"
font-size="324"
id="text14"
sodipodi:linespacing="125%"
style="font-size:427.63009644px;font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;text-align:center;line-height:125%;writing-mode:lr-tb;text-anchor:middle;fill:#000000;font-family:Nimbus Sans L;-inkscape-font-specification:Nimbus Sans L"><tspan
style="font-size:427.63009644px;font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;text-align:center;line-height:125%;writing-mode:lr-tb;text-anchor:middle;font-family:Nimbus Sans L;-inkscape-font-specification:Nimbus Sans L"
id="tspan3017">Read-Mostly, Stale &amp;</tspan></text>
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<text
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y="1350"
font-style="normal"
font-weight="normal"
font-size="324"
id="text16"
sodipodi:linespacing="125%"
style="font-size:427.63009644px;font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;text-align:center;line-height:125%;writing-mode:lr-tb;text-anchor:middle;fill:#000000;font-family:Nimbus Sans L;-inkscape-font-specification:Nimbus Sans L"><tspan
style="font-size:427.63009644px;font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;text-align:center;line-height:125%;writing-mode:lr-tb;text-anchor:middle;font-family:Nimbus Sans L;-inkscape-font-specification:Nimbus Sans L"
id="tspan3019">Inconsistent Data OK</tspan></text>
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<text
xml:space="preserve"
x="7200"
y="1800"
font-style="normal"
font-weight="normal"
font-size="324"
id="text18"
sodipodi:linespacing="125%"
style="font-size:427.63009644px;font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;text-align:center;line-height:125%;writing-mode:lr-tb;text-anchor:middle;fill:#000000;font-family:Nimbus Sans L;-inkscape-font-specification:Nimbus Sans L"><tspan
style="font-size:427.63009644px;font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;text-align:center;line-height:125%;writing-mode:lr-tb;text-anchor:middle;font-family:Nimbus Sans L;-inkscape-font-specification:Nimbus Sans L"
id="tspan3021">(RCU Works Great!!!)</tspan></text>
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<text
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font-style="normal"
font-weight="normal"
font-size="324"
id="text20"
sodipodi:linespacing="125%"
style="font-size:427.63009644px;font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;text-align:center;line-height:125%;writing-mode:lr-tb;text-anchor:middle;fill:#000000;font-family:Nimbus Sans L;-inkscape-font-specification:Nimbus Sans L"><tspan
style="font-size:427.63009644px;font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;text-align:center;line-height:125%;writing-mode:lr-tb;text-anchor:middle;font-family:Nimbus Sans L;-inkscape-font-specification:Nimbus Sans L"
id="tspan3023">(RCU Works Well)</tspan></text>
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<text
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id="text22"
sodipodi:linespacing="125%"
style="font-size:427.63009644px;font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;text-align:center;line-height:125%;writing-mode:lr-tb;text-anchor:middle;fill:#000000;font-family:Nimbus Sans L;-inkscape-font-specification:Nimbus Sans L"><tspan
style="font-size:427.63009644px;font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;text-align:center;line-height:125%;writing-mode:lr-tb;text-anchor:middle;font-family:Nimbus Sans L;-inkscape-font-specification:Nimbus Sans L"
id="tspan3025">Read-Mostly, Need Consistent Data</tspan></text>
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sodipodi:linespacing="125%"
style="font-size:427.63009644px;font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;text-align:center;line-height:125%;writing-mode:lr-tb;text-anchor:middle;fill:#000000;font-family:Nimbus Sans L;-inkscape-font-specification:Nimbus Sans L"><tspan
style="font-size:427.63009644px;font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;text-align:center;line-height:125%;writing-mode:lr-tb;text-anchor:middle;font-family:Nimbus Sans L;-inkscape-font-specification:Nimbus Sans L"
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sodipodi:linespacing="125%">Update-Mostly, Need Consistent Data</text>
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<text
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x="7200"
y="5625"
font-style="normal"
font-weight="normal"
font-size="324"
id="text28"
sodipodi:linespacing="125%"
style="font-size:427.63009644px;font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;text-align:center;line-height:125%;writing-mode:lr-tb;text-anchor:middle;fill:#000000;font-family:Nimbus Sans L;-inkscape-font-specification:Nimbus Sans L"><tspan
style="font-size:427.63009644px;font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;text-align:center;line-height:125%;writing-mode:lr-tb;text-anchor:middle;font-family:Nimbus Sans L;-inkscape-font-specification:Nimbus Sans L"
id="tspan3029">(RCU Might Be OK...)</tspan></text>
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<text
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style="font-size:427.63009644px;font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;text-align:center;line-height:125%;writing-mode:lr-tb;text-anchor:middle;fill:#000000;font-family:Nimbus Sans L;-inkscape-font-specification:Nimbus Sans L"
sodipodi:linespacing="125%">(1) Provide Existence Guarantees For Update-Friendly Mechanisms</text>
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<text
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font-style="normal"
font-weight="normal"
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style="font-size:427.63009644px;font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;text-align:center;line-height:125%;writing-mode:lr-tb;text-anchor:middle;fill:#000000;font-family:Nimbus Sans L;-inkscape-font-specification:Nimbus Sans L"
sodipodi:linespacing="125%">(2) Provide Wait-Free Read-Side Primitives for Real-Time Use)</text>
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<text
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font-weight="normal"
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sodipodi:linespacing="125%">(RCU is Very Unlikely to be the Right Tool For The Job, But it Can:</text>
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28
Documentation/RCU/Design/Requirements/Requirements.html
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@ -1120,12 +1120,27 @@ These classes is covered in the following sections.
<h3><a name="Specialization">Specialization</a></h3>
<p>
RCU is and always has been intended primarily for read-mostly situations, as
illustrated by the following figure.
This means that RCU's read-side primitives are optimized, often at the
RCU is and always has been intended primarily for read-mostly situations,
which means that RCU's read-side primitives are optimized, often at the
expense of its update-side primitives.
Experience thus far is captured by the following list of situations:
<p><img src="RCUApplicability.svg" alt="RCUApplicability.svg" width="70%"></p>
<ol>
<li> Read-mostly data, where stale and inconsistent data is not
a problem: RCU works great!
<li> Read-mostly data, where data must be consistent:
RCU works well.
<li> Read-write data, where data must be consistent:
RCU <i>might</i> work OK.
Or not.
<li> Write-mostly data, where data must be consistent:
RCU is very unlikely to be the right tool for the job,
with the following exceptions, where RCU can provide:
<ol type=a>
<li> Existence guarantees for update-friendly mechanisms.
<li> Wait-free read-side primitives for real-time use.
</ol>
</ol>
<p>
This focus on read-mostly situations means that RCU must interoperate
@ -1171,10 +1186,7 @@ some period of time, so the exact wait period is a judgment call.
One of our pair of veternarians might wait 30 seconds before pronouncing
the cat dead, while the other might insist on waiting a full minute.
The two veternarians would then disagree on the state of the cat during
the final 30 seconds of the minute following the last heartbeat, as
fancifully illustrated below:
<p><img src="2013-08-is-it-dead.png" alt="2013-08-is-it-dead.png" width="431"></p>
the final 30 seconds of the minute following the last heartbeat.
<p>
Interestingly enough, this same situation applies to hardware.

28
Documentation/RCU/Design/Requirements/Requirements.htmlx
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@ -1257,12 +1257,27 @@ These classes is covered in the following sections.
<h3><a name="Specialization">Specialization</a></h3>
<p>
RCU is and always has been intended primarily for read-mostly situations, as
illustrated by the following figure.
This means that RCU's read-side primitives are optimized, often at the
RCU is and always has been intended primarily for read-mostly situations,
which means that RCU's read-side primitives are optimized, often at the
expense of its update-side primitives.
Experience thus far is captured by the following list of situations:
<p><img src="RCUApplicability.svg" alt="RCUApplicability.svg" width="70%"></p>
<ol>
<li> Read-mostly data, where stale and inconsistent data is not
a problem: RCU works great!
<li> Read-mostly data, where data must be consistent:
RCU works well.
<li> Read-write data, where data must be consistent:
RCU <i>might</i> work OK.
Or not.
<li> Write-mostly data, where data must be consistent:
RCU is very unlikely to be the right tool for the job,
with the following exceptions, where RCU can provide:
<ol type=a>
<li> Existence guarantees for update-friendly mechanisms.
<li> Wait-free read-side primitives for real-time use.
</ol>
</ol>
<p>
This focus on read-mostly situations means that RCU must interoperate
@ -1330,10 +1345,7 @@ some period of time, so the exact wait period is a judgment call.
One of our pair of veternarians might wait 30 seconds before pronouncing
the cat dead, while the other might insist on waiting a full minute.
The two veternarians would then disagree on the state of the cat during
the final 30 seconds of the minute following the last heartbeat, as
fancifully illustrated below:
<p><img src="2013-08-is-it-dead.png" alt="2013-08-is-it-dead.png" width="431"></p>
the final 30 seconds of the minute following the last heartbeat.
<p>
Interestingly enough, this same situation applies to hardware.