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>
This commit is contained in:
Paul E. McKenney
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514f1eb5f4
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11a65df573
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id="tspan3025">Read-Mostly, Need Consistent Data</tspan></text>
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id="text26"
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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"
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sodipodi:linespacing="125%">Update-Mostly, Need Consistent Data</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;font-family:Nimbus Sans L;-inkscape-font-specification:Nimbus Sans L"
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id="tspan3029">(RCU Might Be OK...)</tspan></text>
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sodipodi:linespacing="125%">(1) Provide Existence Guarantees For Update-Friendly Mechanisms</text>
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<!-- Text -->
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sodipodi:linespacing="125%">(2) Provide Wait-Free Read-Side Primitives for Real-Time Use)</text>
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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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Before Width: | Height: | Size: 10 KiB |
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@ -1120,12 +1120,27 @@ These classes is covered in the following sections.
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<h3><a name="Specialization">Specialization</a></h3>
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<h3><a name="Specialization">Specialization</a></h3>
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<p>
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<p>
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RCU is and always has been intended primarily for read-mostly situations, as
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RCU is and always has been intended primarily for read-mostly situations,
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illustrated by the following figure.
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which means that RCU's read-side primitives are optimized, often at the
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This means that RCU's read-side primitives are optimized, often at the
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expense of its update-side primitives.
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expense of its update-side primitives.
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Experience thus far is captured by the following list of situations:
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<p><img src="RCUApplicability.svg" alt="RCUApplicability.svg" width="70%"></p>
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<ol>
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<li> Read-mostly data, where stale and inconsistent data is not
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a problem: RCU works great!
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<li> Read-mostly data, where data must be consistent:
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RCU works well.
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<li> Read-write data, where data must be consistent:
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RCU <i>might</i> work OK.
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Or not.
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<li> Write-mostly data, where data must be consistent:
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RCU is very unlikely to be the right tool for the job,
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with the following exceptions, where RCU can provide:
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<ol type=a>
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<li> Existence guarantees for update-friendly mechanisms.
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<li> Wait-free read-side primitives for real-time use.
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</ol>
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</ol>
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<p>
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<p>
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This focus on read-mostly situations means that RCU must interoperate
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This focus on read-mostly situations means that RCU must interoperate
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@ -1171,10 +1186,7 @@ some period of time, so the exact wait period is a judgment call.
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One of our pair of veternarians might wait 30 seconds before pronouncing
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One of our pair of veternarians might wait 30 seconds before pronouncing
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the cat dead, while the other might insist on waiting a full minute.
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the cat dead, while the other might insist on waiting a full minute.
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The two veternarians would then disagree on the state of the cat during
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The two veternarians would then disagree on the state of the cat during
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the final 30 seconds of the minute following the last heartbeat, as
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the final 30 seconds of the minute following the last heartbeat.
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fancifully illustrated below:
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<p><img src="2013-08-is-it-dead.png" alt="2013-08-is-it-dead.png" width="431"></p>
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<p>
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<p>
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Interestingly enough, this same situation applies to hardware.
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Interestingly enough, this same situation applies to hardware.
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@ -1257,12 +1257,27 @@ These classes is covered in the following sections.
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<h3><a name="Specialization">Specialization</a></h3>
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<h3><a name="Specialization">Specialization</a></h3>
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<p>
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<p>
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RCU is and always has been intended primarily for read-mostly situations, as
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RCU is and always has been intended primarily for read-mostly situations,
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illustrated by the following figure.
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which means that RCU's read-side primitives are optimized, often at the
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This means that RCU's read-side primitives are optimized, often at the
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expense of its update-side primitives.
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expense of its update-side primitives.
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Experience thus far is captured by the following list of situations:
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<p><img src="RCUApplicability.svg" alt="RCUApplicability.svg" width="70%"></p>
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<ol>
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|
<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>
|
<p>
|
||||||
This focus on read-mostly situations means that RCU must interoperate
|
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
|
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 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 two veternarians would then disagree on the state of the cat during
|
||||||
the final 30 seconds of the minute following the last heartbeat, as
|
the final 30 seconds of the minute following the last heartbeat.
|
||||||
fancifully illustrated below:
|
|
||||||
|
|
||||||
<p><img src="2013-08-is-it-dead.png" alt="2013-08-is-it-dead.png" width="431"></p>
|
|
||||||
|
|
||||||
<p>
|
<p>
|
||||||
Interestingly enough, this same situation applies to hardware.
|
Interestingly enough, this same situation applies to hardware.
|
||||||
|
|
|
||||||
Loading…
Reference in New Issue