diff options
Diffstat (limited to '2023/08')
| -rw-r--r-- | 2023/08/15/poll-error-attribute-in-OCaml/index.html | 1 | ||||
| -rw-r--r-- | 2023/08/15/tick-thread在Multicore-OCaml中的作用/index.html | 1 | ||||
| -rw-r--r-- | 2023/08/27/二零二三年八月二十七日/index.html | 6 |
3 files changed, 4 insertions, 4 deletions
diff --git a/2023/08/15/poll-error-attribute-in-OCaml/index.html b/2023/08/15/poll-error-attribute-in-OCaml/index.html index a31bde90..d48bc2eb 100644 --- a/2023/08/15/poll-error-attribute-in-OCaml/index.html +++ b/2023/08/15/poll-error-attribute-in-OCaml/index.html @@ -197,7 +197,6 @@ <p>OCaml 编译器提供了一个名为 <a target="_blank" rel="noopener" href="https://github.com/ocaml/ocaml/pull/10462"><code>[@poll error]</code></a> 的annotation，可以在函数中使用它来确保该函数不包含safe point。</p> <p>所以通过使用 <code>[@poll error]</code> 就可以创建在Domain内原子性执行的函数，也就是说，基于此特性可以实现单个Domain内线程安全的数据结构，例如 thread-table 便是使用这个特性实现的 Hash Table。可以看看它的 add 函数的实现:</p> <figure class="highlight ocaml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">let</span>[@poll error] add_atomically t buckets n i before after =</span><br><span class="line"> t.rehash = <span class="number">0</span> && buckets == t.buckets</span><br><span class="line"> && before == <span class="type">Array</span>.unsafe_get buckets i</span><br><span class="line"> && <span class="keyword">begin</span></span><br><span class="line"> <span class="type">Array</span>.unsafe_set buckets i after;</span><br><span class="line"> <span class="keyword">let</span> length = t.length + <span class="number">1</span> <span class="keyword">in</span></span><br><span class="line"> t.length <- length;</span><br><span class="line"> <span class="keyword">if</span> n < length && n < max_buckets_div_2 <span class="keyword">then</span> t.rehash <- n * <span class="number">2</span>;</span><br><span class="line"> <span class="literal">true</span></span><br><span class="line"> <span class="keyword">end</span></span><br><span class="line"></span><br><span class="line"><span class="keyword">let</span> <span class="keyword">rec</span> add t k' v' =</span><br><span class="line"> <span class="keyword">let</span> h = <span class="type">Mix</span>.<span class="built_in">int</span> k' <span class="keyword">in</span></span><br><span class="line"> maybe_rehash t;</span><br><span class="line"> <span class="keyword">let</span> buckets = t.buckets <span class="keyword">in</span></span><br><span class="line"> <span class="keyword">let</span> n = <span class="type">Array</span>.length buckets <span class="keyword">in</span></span><br><span class="line"> <span class="keyword">let</span> i = h <span class="keyword">land</span> (n - <span class="number">1</span>) <span class="keyword">in</span></span><br><span class="line"> <span class="keyword">let</span> before = <span class="type">Array</span>.unsafe_get buckets i <span class="keyword">in</span></span><br><span class="line"> <span class="keyword">let</span> after = <span class="type">Cons</span> (k', v', before) <span class="keyword">in</span></span><br><span class="line"> <span class="keyword">if</span> not (add_atomically t buckets n i before after) <span class="keyword">then</span> add t k' v'</span><br></pre></td></tr></table></figure> - <p>相比使用 Stdlib.Mutex，这种无锁实现会有更好的性能（特别是对于只读操作），并且还允许例如信号处理之类的上下文操作。</p> </div> diff --git a/2023/08/15/tick-thread在Multicore-OCaml中的作用/index.html b/2023/08/15/tick-thread在Multicore-OCaml中的作用/index.html index fa346797..decea234 100644 --- a/2023/08/15/tick-thread在Multicore-OCaml中的作用/index.html +++ b/2023/08/15/tick-thread在Multicore-OCaml中的作用/index.html @@ -194,7 +194,6 @@ <div class="post-content"> <p>Multicore OCaml的程序在启动时会运行一个 tick thread，其实现如下:</p> <figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* The tick thread: posts a SIGPREEMPTION signal periodically */</span></span><br><span class="line"></span><br><span class="line"><span class="type">static</span> <span class="type">void</span> * <span class="title function_">caml_thread_tick</span><span class="params">(<span class="type">void</span> * arg)</span></span><br><span class="line">{</span><br><span class="line"> <span class="class"><span class="keyword">struct</span> <span class="title">timeval</span> <span class="title">timeout</span>;</span></span><br><span class="line"> <span class="type">sigset_t</span> mask;</span><br><span class="line"></span><br><span class="line"> <span class="comment">/* Block all signals so that we don't try to execute an OCaml signal handler*/</span></span><br><span class="line"> sigfillset(&mask);</span><br><span class="line"> pthread_sigmask(SIG_BLOCK, &mask, <span class="literal">NULL</span>);</span><br><span class="line"> <span class="keyword">while</span>(! caml_tick_thread_stop) {</span><br><span class="line"> <span class="comment">/* select() seems to be the most efficient way to suspend the</span></span><br><span class="line"><span class="comment"> thread for sub-second intervals */</span></span><br><span class="line"> timeout.tv_sec = <span class="number">0</span>;</span><br><span class="line"> timeout.tv_usec = Thread_timeout * <span class="number">1000</span>;</span><br><span class="line"> select(<span class="number">0</span>, <span class="literal">NULL</span>, <span class="literal">NULL</span>, <span class="literal">NULL</span>, &timeout);</span><br><span class="line"> <span class="comment">/* The preemption signal should never cause a callback, so don't</span></span><br><span class="line"><span class="comment"> go through caml_handle_signal(), just record signal delivery via</span></span><br><span class="line"><span class="comment"> caml_record_signal(). */</span></span><br><span class="line"> caml_record_signal(SIGPREEMPTION);</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> <span class="literal">NULL</span>;</span><br><span class="line">}</span><br></pre></td></tr></table></figure> - <p>这是因为Multicore OCaml的GC目前需要一个进程（或一个Domain）中的所有线程一起参与以避免并发访问。如果一个线程在system call上被阻塞，那么整个Domain就会被卡住，直到该线程可以参与当前的垃圾收集。为了避免这个问题，tick 线程可以代替被阻塞的线程执行垃圾收集操作。</p> </div> diff --git a/2023/08/27/二零二三年八月二十七日/index.html b/2023/08/27/二零二三年八月二十七日/index.html index 0a1837e8..3efbd1bf 100644 --- a/2023/08/27/二零二三年八月二十七日/index.html +++ b/2023/08/27/二零二三年八月二十七日/index.html @@ -184,9 +184,11 @@ </div> </div> <div class="post-content"> - <p>我从失去家人的那一刻就坠入了一个朦胧而美丽的梦，梦境没有主人，我是被梦境所留下的，永远不愿醒来的旅人。<br>我足不出户，一直缩在一方小世界里面，我用了无数的理由和所有人说我的生活态度，其实勇敢的人根本不需要理由就能走出去，只有懦弱的人会用各种理由说服自己退缩</p> + <p>我从失去家人的那一刻就坠入了一个朦胧而美丽的梦，梦境没有主人，我是被梦境所留下的，永远不愿醒来的旅人。<br> +我足不出户，一直缩在一方小世界里面，我用了无数的理由和所有人说我的生活态度，其实勇敢的人根本不需要理由就能走出去，只有懦弱的人会用各种理由说服自己退缩</p> <p>请以我为戒，大胆往前走，走到灯火通明。</p> -<p>何须纵酒方能舞翩迁，<br>赤诚相见时便是少年。</p> +<p>何须纵酒方能舞翩迁，<br> +赤诚相见时便是少年。</p> </div> |