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| -rw-r--r-- | Documentation/RCU/Design/Requirements/2013-08-is-it-dead.png | bin | 100825 -> 0 bytes | |||
| -rw-r--r-- | Documentation/RCU/Design/Requirements/RCUApplicability.svg | 237 | ||||
| -rw-r--r-- | Documentation/RCU/Design/Requirements/Requirements.html | 28 | ||||
| -rw-r--r-- | Documentation/RCU/Design/Requirements/Requirements.htmlx | 28 |
4 files changed, 40 insertions, 253 deletions
diff --git a/Documentation/RCU/Design/Requirements/2013-08-is-it-dead.png b/Documentation/RCU/Design/Requirements/2013-08-is-it-dead.png Binary files differdeleted file mode 100644 index 7496a55e4e7b..000000000000 --- a/Documentation/RCU/Design/Requirements/2013-08-is-it-dead.png +++ /dev/null diff --git a/Documentation/RCU/Design/Requirements/RCUApplicability.svg b/Documentation/RCU/Design/Requirements/RCUApplicability.svg deleted file mode 100644 index ebcbeee391ed..000000000000 --- a/Documentation/RCU/Design/Requirements/RCUApplicability.svg +++ /dev/null @@ -1,237 +0,0 @@ -<?xml version="1.0" encoding="UTF-8" standalone="no"?> -<!-- Creator: fig2dev Version 3.2 Patchlevel 5d --> - -<!-- CreationDate: Tue Mar 4 18:34:25 2014 --> - -<!-- Magnification: 3.000 --> - -<svg - xmlns:dc="http://purl.org/dc/elements/1.1/" - xmlns:cc="http://creativecommons.org/ns#" - xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" - xmlns:svg="http://www.w3.org/2000/svg" - xmlns="http://www.w3.org/2000/svg" - 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inkscape:window-maximized="0" - inkscape:current-layer="g4" - fit-margin-top="5" - fit-margin-left="5" - fit-margin-right="5" - fit-margin-bottom="5" /> - <g - style="fill:none;stroke-width:0.025in" - id="g4" - transform="translate(-2043.6828,14.791398)"> - <!-- Line: box --> - <rect - x="0" - y="0" - width="14400" - height="8775" - rx="0" - style="fill:#ffa1a1;stroke:#000000;stroke-width:21;stroke-linecap:butt;stroke-linejoin:miter" - id="rect6" /> - <!-- Line: box --> - <rect - x="1350" - y="0" - width="11700" - height="6075" - rx="0" - style="fill:#ffff00;stroke:#000000;stroke-width:21;stroke-linecap:butt;stroke-linejoin:miter" - id="rect8" /> - <!-- Line: box --> - <rect - x="2700" - y="0" - width="9000" - height="4275" - rx="0" - style="fill:#00ff00;stroke:#000000;stroke-width:21;stroke-linecap:butt;stroke-linejoin:miter" - id="rect10" /> - <!-- Line: box --> - <rect - x="4050" - y="0" - width="6300" - height="2475" - rx="0" - style="fill:#87cfff;stroke:#000000;stroke-width:21;stroke-linecap:butt;stroke-linejoin:miter" - id="rect12" /> - <!-- Text --> - <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 &</tspan></text> - <!-- Text --> - <text - xml:space="preserve" - x="7200" - 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> - <!-- Text --> - <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> - <!-- Text --> - <text - xml:space="preserve" - x="7200" - y="3825" - 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> - <!-- Text --> - <text - xml:space="preserve" - x="7200" - y="3375" - font-style="normal" - font-weight="normal" - font-size="324" - 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> - <!-- Text --> - <text - xml:space="preserve" - x="7200" - y="5175" - font-style="normal" - font-weight="normal" - font-size="324" - id="text24" - 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="tspan3027">Read-Write, Need Consistent Data</tspan></text> - <!-- Text --> - <text - xml:space="preserve" - x="7200" - y="6975" - font-style="normal" - font-weight="normal" - font-size="324" - id="text26" - 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%">Update-Mostly, Need Consistent Data</text> - <!-- Text --> - <text - xml:space="preserve" - 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> - <!-- Text --> - <text - xml:space="preserve" - x="7200" - y="7875" - font-style="normal" - font-weight="normal" - font-size="324" - id="text30" - 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> - <!-- Text --> - <text - xml:space="preserve" - x="7200" - y="8325" - font-style="normal" - font-weight="normal" - font-size="324" - id="text32" - 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> - <!-- Text --> - <text - xml:space="preserve" - x="7200" - y="7425" - font-style="normal" - font-weight="normal" - font-size="324" - id="text34" - 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%">(RCU is Very Unlikely to be the Right Tool For The Job, But it Can:</text> - </g> -</svg> diff --git a/Documentation/RCU/Design/Requirements/Requirements.html b/Documentation/RCU/Design/Requirements/Requirements.html index 01e12b86e81f..c67a96a2a389 100644 --- a/Documentation/RCU/Design/Requirements/Requirements.html +++ b/Documentation/RCU/Design/Requirements/Requirements.html @@ -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. diff --git a/Documentation/RCU/Design/Requirements/Requirements.htmlx b/Documentation/RCU/Design/Requirements/Requirements.htmlx index 3355f1f9384c..d6a84f3e0451 100644 --- a/Documentation/RCU/Design/Requirements/Requirements.htmlx +++ b/Documentation/RCU/Design/Requirements/Requirements.htmlx @@ -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. |
