hashbrowncipher

#!/bin/bash

# As the "bufferbloat" folks have recently re-discovered and/or more widely
# publicized, congestion avoidance algorithms (such as those found in TCP) do
# a great job of allowing network endpoints to negotiate transfer rates that
# maximize a link's bandwidth usage without unduly penalizing any particular
# stream. This allows bulk transfer streams to use the maximum available
# bandwidth without affecting the latency of non-bulk (e.g. interactive)
# streams.

hashbrowncipher

#!/bin/bash
set -x
set -o errexit
set -o nounset
set -o pipefail

#------- end of header (relevant for root/kernel.sh, below)

readonly INITRD_DIR=initrd
readonly SSH_KEY="ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIIyK5qcNzv65trF8pdiLZbnBS6NLJqiHhGSQo6veOswH"

hashbrowncipher

#!/bin/bash
set -x
set -o errexit
set -o nounset
set -o pipefail

readonly INITRD_DIR=initrd

base() {
    debootstrap \

hashbrowncipher

#include <linux/hrtimer.h>
#include <linux/module.h>
#include <linux/kernel.h>

static struct hrtimer timer;

enum hrtimer_restart yell_rick( struct hrtimer *timer )
{
        ktime_t time;
        printk(KERN_INFO "I turned myself into a logger morty! I'm dmesg RIIIICK!\n");

hashbrowncipher

diff --git a/src/main/java/com/tagtraum/perf/gcviewer/view/renderer/TotalTenuredRenderer.java b/src/main/java/com/tagtraum/perf/gcviewer/view/renderer/TotalTenuredRenderer.java
index 344965d..f8e31a0 100644
--- a/src/main/java/com/tagtraum/perf/gcviewer/view/renderer/TotalTenuredRenderer.java
+++ b/src/main/java/com/tagtraum/perf/gcviewer/view/renderer/TotalTenuredRenderer.java
@@ -49,6 +49,8 @@ public class TotalTenuredRenderer extends PolygonChartRenderer {
                         polygon.addPoint(0, (double)tenured.getTotal());
                     }
                     polygon.addPoint(tenured.getTimestamp() - model.getFirstPauseTimeStamp() + event.getPause(),
+                            lastTotal);
+                    polygon.addPoint(tenured.getTimestamp() - model.getFirstPauseTimeStamp() + event.getPause(),

hashbrowncipher

package com.josnyder;

import java.lang.management.ManagementFactory;
import javax.management.InstanceAlreadyExistsException;
import javax.management.MBeanServer;
import javax.management.ObjectName;
import org.apache.cassandra.service.CassandraDaemon;

class HotspotMBeanCassandraDaemon extends CassandraDaemon {
    protected void setup() {

hashbrowncipher

$ sudo ./ocperf.py stat -e cpu_clk_thread_unhalted.ref_xclk,cpu_clk_thread_unhalted.ref_xclk_any,cpu_clk_unhalted.one_thread_active -a -- sleep 5
perf stat -e cpu/event=0x3c,umask=0x1,name=cpu_clk_thread_unhalted_ref_xclk/,cpu/event=0x3c,umask=0x1,any=1,name=cpu_clk_thread_unhalted_ref_xclk_any/,cpu/event=0x3c,umask=0x2,name=cpu_clk_unhalted_one_thread_active/ -a -- sleep 5

 Performance counter stats for 'system wide':

       295,538,267 cpu_clk_thread_unhalted_ref_xclk                                    [100.00%]
       579,495,176 cpu_clk_thread_unhalted_ref_xclk_any                                    [100.00%]
       283,950,270 cpu_clk_unhalted_one_thread_active

       5.000637559 seconds time elapsed

hashbrowncipher

//A parallel version of find(1), implementing a DFS-ish over cwd.
//Compile with -lpthread

#include <dirent.h>
#include <fcntl.h>
#include <pthread.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>

hashbrowncipher

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs

hashbrowncipher

Eden Sizing

There are limits to the size that Eden is allowed to be. Those limits are calculated in calculate_default_min_length:
G1YoungGenSizer::recalculate_min_max_young_length -> G1YoungGenSizer::calculate_default_min_length

G1CollectorPolicy::update_young_list_target_length is responsible for
determining the actual size of the young list. If doing a young GC, it will
call G1CollectorPolicy::calculate_young_list_target_length. This function
attempts to find the largest eden size that will allow (predicted) GC pauses to
remain under the pause time target. Presumably after a certain eden size, there