Flying across America provides a bird’s eye view of how we humans have decided to cut the land up. In regions where we’ve completely mastered the topography, you’ll see completely unnatural-looking, perfect grids like this, punctuated with perfect circles:
So what the heck are those, and how/why are they created? Here’s the 30-second answer:
That’s a snippet from this five-minute-plus video on why certain parts of America look very different from the air, depending on which colonial master first took control of which region. It’s worth a watch if you’ve got the time.
Dash cams range from tiny units without screens that hide behind the rearview mirror to models with relatively large displays and a multitude of features. Here are the key features and specs to consider when you’re shopping.
Resolution and image sensor: The image quality of dash cams keeps improving. When we first published this guide in 2014, the best models had a maximum resolution of 1080p, with many models reaching only 720p. This time around, all of the models we tested could record at 1080p, with several able to capture a notably sharper 1296p and one capable of 1440p. In the higher-resolution models, we could see a clear difference in detail, and we were better able to read license plates and street signs, even when in motion. (You can set a cam’s resolution lower to take up less space on the storage card if you prefer.) The best cams also have image sensors and processors that provide a wide dynamic range that retains detail in both lighter and darker areas, as well as good color and contrast and low video noise across a variety of lighting and weather conditions.
These photos show the field-of-view range in our test group. The Papago GoSafe 228’s narrow 120-degree FOV gives you a closer look at things right in front of your car but misses things at the sides. Photo: Rik Paul
The 160-degree FOV of the Papago GoSafe 535 strikes a nice balance between width and center details. Photo: Rik Paul
The widest we saw was the Garmin Dash Cam 65W’s 180-degree FOV, which makes center objects look farther away but can be nice for capturing scenic landscapes as you drive. Photo: Rik Paul
Field of view (FOV): The models we tested have a field of view that ranges from a relatively narrow 120 degrees to a wide 180 degrees. The wider the field of view, the more of the scene that a camera can capture, which is handy for scenic vistas, sunsets, and the like. The trade-off is that wider FOVs make cars in front look a little farther away, although in our tests the sharp resolution of the best cams still made it easy to read license plates and see other details. The 160-degree FOV in our top pick is a good compromise.
Mounting: Most cameras mount to a car’s windshield in one of two ways: suction or adhesive. Some models give you a choice, while others come with only one or the other. Adhesive mounts often attach directly to the camera, which reduces the unit’s overall size. This design typically permits more-discreet placement, so the camera doesn’t intrude as much into your view, and the camera isn’t as noticeable from the outside. The ones we tested adhered very well to glass. But adhesive mounts can be difficult to remove, sometimes requiring a razor blade or a sharp paint scraper along with some patience, so you can’t easily move the camera from one car to another. Adhesive mounts also require precise placement when you install them, since you can’t adjust the placement without a lot of hassle or buying new adhesive material.
We favor a suction mount, even though the cam hangs down lower from one, because it has two key advantages: You can aim and adjust it easily, and you can remove it quickly if you want to take it down for any reason. (For instance, perhaps you have to park overnight on a street or in a lot, and you’re concerned about theft. Or you want to be able to move the camera between cars, such as for use in a rental car.)
Whatever the mount type, you want the camera to have good build quality and to remain firmly in place once positioned, so that it’s not easily jostled if you or your passengers accidentally nudge it or if your car hits a rough spot in the road.
Regardless of the mount, all models come with a long power cord that you can route to a power source. To keep it out of sight, you can often hide this cord behind the windshield molding and interior trim, but doing so can be the most challenging part of installing a dash cam. Alternatively, you can buy cord clips for a few bucks to route it out of the way, or Best Buy’s Geek Squad will install a dash cam for about $50.
Size: A dash cam and its mount should be somewhat discreet so they don’t take up too much real estate on your windshield and don’t distract you while you’re driving. The best units we looked at provide at least a small display while not blocking too much of the driver’s view.
Display: Most of the dash cams we tested have a display that’s 1.5 to 2.7 inches, measured diagonally; one model doesn’t have a display at all. We prefer dash cams with at least a 2-inch display, which makes it easier to adjust settings on the fly and preview footage. A lack of a display means that you have to use a computer, before getting into the car, to adjust the settings. The absence of a display also makes it hard to know if the camera angle is right without reviewing the footage on a separate device. And it’s impossible to know if the camera is really recording.
We tested three models that have separate cameras you can mount to your vehicle’s rear window to record what’s going on behind your car. Photo: Rik Paul
Second cam: Some dash cams—called dual-channel models—are able to record from two cameras simultaneously, which is helpful for recording both what’s in front of the car as well as what’s behind it or inside the vehicle. Models that record behind the car have two separate camera enclosures, one for mounting on the windshield and one for the rear window. The rear camera can also serve as a backup camera; you can display the footage from either camera on the screen or use the picture-in-picture function.
Some models have two cameras integrated into one housing, one for recording in front and the other pointing rearward toward the car’s cabin and passengers. This design can be helpful for taxi, Uber, Lyft, and other ride-for-hire drivers who have to deal with the occasional unruly customer, although the footage can be too dark to clearly see rear-seat passengers at night.
Storage cards: About half of the dash cams we tested come with an 8 GB microSD memory card, although some include a more generous 32 GB. Some models don’t include any card, which increases the cam’s effective price. Most of the cams accept a larger card of 64 or 128 GB, which is an important consideration.
A larger memory card lets you capture more footage before the cam needs to overwrite older video. At its maximum 1296p resolution, the Papago GoSafe 535 (our top pick) captures less than an hour of video on its 8 GB card (or a little over three hours when you set it at the lower, 720p resolution). That might work if all you want to do is record an accident or an occasional interesting scene, or if you expect to offload the footage frequently. But if you don’t want your video overwritten so quickly, we recommend getting a larger card; a quality 64 GB microSD card will set you back about $20 currently.
Battery versus capacitor: All of the models we tested get power when you plug their 12 V adapter into your car’s 12-volt accessory outlet (the “cigarette lighter”), although some can be hardwired if you desire. Most also have an internal lithium-ion battery that lets them continue to record for a period of time if the cord is unplugged. But in extreme temperature conditions, where objects left baking in a car can reach 180 to 200 °F, these batteries can overheat and need to be cooled to perform well. They can also suffer in very low temperatures, when they’re too cold to function right away. To help in these types of situations, some models use a capacitor, which better handles extreme temperatures and provides more reliability in those conditions than a battery. The downside is that, without a battery, a capacitor cam can’t continue working when it’s unplugged; the camera will power down after a few seconds.
Automatic incident detection: All of the dash cams we tested have built-in G-sensors that detect an impact and automatically save the footage of the incident. In most cases, the cam protects this footage from being overwritten, as well, so you have the evidence should you need it.
Parking surveillance: Models with this feature use optical motion detection or G-sensors to “wake up” and start recording if something happens to or around your vehicle while it’s parked. But the odds of the camera picking up useful information are low, since the camera faces a single direction and also requires persistent power to do this. We tested the parking mode in the models that offered it, but we were unable to trigger any of the cameras. Car owners shouldn’t consider this feature a reliable security tool.
Wi-Fi: You can view footage directly on your smartphone via an ad-hoc Wi-Fi network the camera provides. This feature is convenient if you want to share video or photos on social media, but it’s more of a frill than a necessity. Dash cams with Wi-Fi typically have a companion smartphone app, where you can look at the footage.
GPS: Models with a GPS receiver typically stamp the video with geographic coordinates, as well as the vehicle’s speed and direction of travel. Some also show the vehicle’s location on a map in the model’s compatible computer software. The GPS feature doesn’t provide turn-by-turn directions, however (for that you need a dedicated car GPS navigator). This info can be useful to verify the location of an incident or to mark a site where you captured a specific view or happening. But if you’re interested only in recording what’s in front of your car, GPS is just an extra.
Safety features: Some dash cams (and car GPS devices) provide safety alerts similar to the type that are becoming more common in newer cars. These include forward-collision warnings, which sound an audible alert if you are following another car too closely, and lane-departure warnings, which let you know if your car is crossing a lane marker on the road. Both can be helpful in some situations, but as you might expect, these features on a dash cam aren’t as reliable, consistent, or sophisticated as the more expensive safety systems in new cars. In some dash cam models, the alerts are also overly sensitive, which causes them to go off too often and can make them annoying enough that you want to turn them off. Again, this feature is not really a necessity for most people.
The LG 27UD68P-B is the best 4K monitor for most people because of its great color and grayscale measurements, thin bezels, three-way adjustable stand, and easy-to-use menus. It also has FreeSync adaptive sync, which makes it even better for gaming if you have an AMD video card. The LG doesn’t have USB 3.0 hub and its grayscale tracking isn’t as good as our runner-up pick’s, although its color accuracy is much better. At a price comparable with monitors with lower resolutions, this is a great display for anyone ready to make the jump to 4K.
The LG ColorChecker indicates some visible inaccuracies in some yellow and orange shades.
The 27UD68P-B is factory calibrated, and out of the box images are color-accurate and detailed. In the color saturation test, the 27UD68P-B had an overall DeltaE value of 1.94. Above 80 percent brightness, though, the individual DeltaE values for red, green, and yellow creep up toward 3.0, and yellow hits that number at 100 percent color saturation. That means you’ll see slightly inaccurate yellows in more vivid images—a picture of a field of sunflowers will look a bit unnatural. The ColorChecker test—which measures the accuracy of over 100 colors representing skin tones, the sky, and other natural elements—had a DeltaE of 2.35, and the number for primary and secondary color points was 2.25. Grayscale tracking average was 2.31, with a slightly higher number at increased brightness levels—it’s very good below 50 percent brightness.
Grayscale tracking on the LG 27UD68P-B, especially below 50 percent brightness, is very good, although not as accurate as the Dell U2718Q, our runner-up.
Contrast ratio is the measurement of a fully lit white screen versus an unlit black screen at a fixed brightness level. The contrast ratio of the 27UD68P-B, at 1186:1, was the highest of all the monitors we tested. This is an excellent number for a monitor, especially an IPS panel, and it means the bright parts of the screen will look vibrant and really pop out next to blacks (think images of fireworks in a night sky).
The LG 27UD68P-B has a wide luminance range. At its highest brightness setting, a full white field on the monitor outputs 287 cd/m² of light—slightly under LG’s claimed 300 cd/m², but still enough for a sunlit room. At its lowest, the monitor light output drops to 59 cd/m², which will limit the fatigue on your eyes while playing Overwatch in a dark room.
The 27UD68P-B is VESA-compatible and has a stand that can adjust height, tilt, and pivot. The stand has 4.7 inches of height adjustment, up to a maximum height of 21.13 inches from the top of the screen to the desktop. The monitor can tilt forward 5 degrees or back 20 degrees and can pivot clockwise into a portrait position. Unlike the stands of our Dell or Benq picks, the stand cannot swivel.
The on-screen display’s layout corresponds nicely with the joystick control, making navigation easy. Photo: Kyle Fitzgerald
Like recent monitors from Dell and HP, the 27UD68P-B has very thin side and top bezels, at just over a quarter of an inch thick on the top and sides (8 mm), though the .9-inch (23 mm) bottom bezel is significantly larger. Unlike most monitors, which are controlled with a line of buttons along the lower right of the frame, the 27UD68P-B has a four-way joystick situated underneath the bottom bezel at the center. It took a short while to get used to, but once we did we loved the ease of use. Menu navigation is quick, and being able to keep your finger in one place to move through every menu option is convenient. It’s far better than the capacitive buttons many monitor makers use.
All menu navigation is done with this joystick underneath the display. Photo: Kyle Fitzgerald
The LG has one DisplayPort 1.2 port and two HDMI 2.0 inputs for connecting computers or other A/V sources, like a PlayStation 4 Pro or a 4K-capable Roku or Apple TV box, but it’s missing the USB 3.0 hub and the Mini DisplayPort found on both the Dell U2718Q and BenQ PD3200U.The only additional port is a headphone-out jack for audio streams sent over DisplayPort or HDMI. The volume level can be controlled by moving the joystick toggle left and right. All of the connections are on the back of the monitor, so if you need to regularly plug and unplug cables it could be tedious.
A/V connections come out the back of the monitor rather than underneath, as on the Dell, or from the side, like the BenQ. Photo: Kyle Fitzgerald
There are a few options on the 27UD68P-B that cater to gamers. The most prominent is FreeSync, which reduces screen tearing by locking the refresh rate of the monitor to the frame rate of the video card. It’s supported only over DisplayPort, not HDMI, and must be connected to either a discrete graphics card or an integrated GPU that supports it; right now, the only CPUs and GPUs that support the technology come from AMD. (Nvidia has its own adaptive-sync technology, called G-Sync, which requires both an Nvidia graphics card and a monitor with a special chip in it.)
Another gaming-oriented menu option is called Black Stabilizer. It boosts the brightness in darker gray areas of the screen, which could help keep you alive during those long online gaming sessions, especially if the room you’re playing in has ambient light that makes it difficult to distinguish the shadows on screen. We don’t recommend using the feature for anything other than gaming, though, as it sacrifices black level accuracy for an edge in gaming combat.
The LG 27UD68P-B has a one-year parts and labor warranty. LG will either repair or replace the unit, at its discretion, but it doesn’t have a bright/dead pixel policy (see “Flaws but not dealbreakers,” below). 144HzMonitors.com named it the Best 4K IPS FreeSync Monitor, MonitorNerds named it the Best 4K Gaming Monitor, and 4K.com found it to have “superb performance quality almost entirely across the board.” RTings.com gave it a good score for mixed usage—this monitor is good at just about everything.
LG sells two monitors nearly identical to the 27UD68P-B. The 27UD68-W is the same monitor with a white case and silver-colored stand, and the 27UD68-P has a stand without height or pivot adjustments. It does have VESA mounts, though, and it’s often a little cheaper than the 27UD68P-B, so it’s a good choice if you already have a monitor arm you like.
The gun gurus at USA Today attempted to explain, for some reason, not only the features of the Ruger AR-15 used by the demented coward responsible for the Texas church massacre, but the “possible modifications” one can make to an AR as well. Including, naturally, the ever-popular chainsaw bayonet.
Wait. What? Yup. This actually happened. See USA Today’s video below, followed by a small sampling of the internet’s hilarious, meme-laden response…
To be fair, chainsaw bayonets do actually exist. I mean, they’re an $800 gag gift movie prop but, much to everyone’s surprise, somebody did really design one and does [attempt to] sell them.
In this blog post, I’ll look at MySQL and Linux context switches and what is the normal number per second for a database environment.
You might have heard many times about the importance of looking at the number of context switches to indicate if MySQL is suffering from the internal contention issues. I often get the question of what is a “normal” or “acceptable” number, and at what point should you worry about the number of context switches per second?
First, let’s talk about what context switches are in Linux. This StackOverflow Thread provides a good discussion, with a lot of details, but basically it works like this:
The process (or thread in MySQL’s case) is running its computations. Sooner or later, it has to do some blocking operation: disk IO, network IO, block waiting on a mutex or yield. The execution switches to the other process, and this is called voluntary context switch.On the other hand, the process/thread may need to be preempted by the scheduler because it used an allotted amount of CPU time (and now other tasks need to run) or because it is required to run high priority task. This is called involuntary context switches. When all the process in the system are added together and totaled, this is the system-wide number of context switches reported (using, for example, vmstat):
root@nuc2:~# vmstat 10
procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu-----
r b swpd free buff cache si so bi bo in cs us sy id wa st
17 0 0 12935036 326152 2387388 0 0 0 5 0 1 9 0 91 0 0
20 0 0 12933936 326152 2387384 0 0 0 3 32228 124791 77 22 1 0 0
17 0 0 12933348 326152 2387364 0 0 0 11 33212 124575 78 22 1 0 0
16 0 0 12933380 326152 2387364 0 0 0 78 32470 126100 78 22 1 0 0
This is a global number. In many cases, however, it is better to look at it as context switches per CPU logical core. This is because cores execute tasks independently. As such, they have mostly independent causes for context switches. If you have a large number of cores, there can be quite a difference:
The number of context switches per second on this system looks high (at more than 1,000,000). Considering it has 56 logical cores, however, it is only about 30,000 per second per logical core (which is not too bad).
So how do we judge if the number of context switches is too high in your system? One answer is that it is too high if you’re wasting too much CPU on context switches. This brings up the question: how many context switches can the system handle if it is only doing context switches?
It is easy to find this out!
Sysbench has a “threads” test designed specifically to measure this. For example:
sysbench --thread-locks=128 --time=7200 --threads=1024 threads run
Check the vmstat output or the Context Switches PMM graph:
We can see this system can handle up to 35 million context switches per second in total (or some 500K per logical CPU core on average).
I don’t recommend using more than 10% of CPU resources on context switching, so I would try to keep the number of the context switches at no more than 50K per logical CPU core.
Now let’s think about context switches from the other side: how many context switches do we expect to have at the very minimum for given load? Even if all the stars align and your query to MySQL doesn’t need any disk IO or context switches due to waiting for mutexes, you should expect at least two context switches: one to the client thread which processes the query and one for the query response sent to the client.
Using this logic, if we have 100,000 queries/sec we should expect 200,000 context switches at the very minimum.
In the real world, though, I would not worry about contention being a big issue if you have less than ten context switches per query.
It is worth noting that in MySQL not every contention results in a context switch. InnoDB implements its own mutexes and RW-locks, which often try to “spin” to wait for a resource to become available. This wastes CPU time directly rather than doing a context switch.
Summary:
Look at the number of context switches per logical core rather than the total for easier-to-compare numbers
Find out how many context switches your system can handle per second, and don’t get too concerned if your context switches are no more than 10% of that number
Think about the number of context switches per query: the minimum possible is two, and values less than 10 make contention an unlikely issue
Not every MySQL contention results in a high number of context switches
At first glance, the HC3R magazine looks like any other 25-rounder for Ruger 10-22. Flip it over, and the unusual structure suggests uncommon features.
These magazines can be loaded two ways. The first is like any other; the follower is held down and 25 individual cartridges inserted through the feed lips. This method is fairly slow but it works fine.
In my experience, it reliably fed a variety of ammunition profiles while shooting a 10/22.
Once the magazine has been emptied, lock the magazine follower at the bottom of the curved body, then push down on the ribbed release latch near the feed tower to free a 20-shot en block clip.
The molded raceway holds additional ammunition securely and safe from dust on the inside of the magazine.
Insert the loaded clip into the back of the magazine, then unlock the follower and lower it gently. The magazine is now ready for action. This operation can be done with the magazine still in the action.
Loading the clips can be done manually, but you can do it much more quickly by placing 20 cartridges into the clip pocket, then scooping them up with the opening of the clip. The entire process takes a couple of seconds without any risk of deforming the bullets by spring pressure. Fully loaded, an HC3R magazine holds 25 rounds ready to fire, and 20 in close reserve.
Not only is the loading process quite simple, it also provides a fairly affordable and lightweight method for carrying rimfire ammunition. MSRP for the magazine with one clip is $30, and a 5-pack of clips holding 100 rounds total runs $20 — so the total capacity for one magazine and six clips would be 145 rounds.
While the story out of Sutherland Springs is heartbreaking, more astute folks are noting that it could have been worse. After all, when the killer had completed with the carnage inside, he stepped out of the church and into the sights of a man named Stephen Willeford who lived near the First Baptist Church.
Willeford was at home when his daughter came into his bedroom to tell him she heard gunshots at the First Baptist Church nearby.
Willeford, a former NRA instructor, got his rifle out of his safe while his daughter looked outside again. She ran back in and told him she saw a man in black tactical gear shooting up the church.
“I kept hearing the shots, one after another, very rapid shots – just ‘pop pop pop pop’ and I knew every one of those shots represented someone, that it was aimed at someone, that they weren’t just random shots,” Willeford said.”
Willeford loaded his magazine and ran across the street to the church, not even taking the time to put on shoes. When Willeford saw the gunman, he exchanged gunfire.
“He saw me and I saw him,” Willeford said. “I was standing behind a pickup truck for cover.”
“I know I hit him,” Willeford said. “He got into his vehicle, and he fired another couple rounds through his side window. When the window dropped, I fired another round at him again.”
As the gunman sped away, Willeford approached a pickup truck at a stop sign.
“That guy just shot up the Baptist church. We need to stop him,” he said. Together, Willeford and the driver took off in pursuit. As they caught up to the killer’s vehicle, the truck slowed down. It then sped up eventually went off the road, flipping over into a ditch.
Willeford says he yelled out for the shooter to exit the vehicle, but he didn’t.
That’s because the 26-year-old killer had apparently taken his own life.
In the coming days, as we have seen over the hours since news of this tragedy broke, there will be those who will seek to disarm law-abiding citizens. It’s important that we remember that were it not for Stephen Willeford, the tragedy could have been worse. We’ll never know how much worse it could have been because of his bravery.
Those same voices would have disarmed Willeford. Those same voices would disarm the countless people he’s trained to respond similarly to hostile actions as an NRA instructor.
Willeford has said that he isn’t a hero, but that’s a mistake. He’s the epitome of a good guy with a gun, and that alone makes him a hero. We don’t know how many lives were saved because of his courage and decision to take his personal safety into his own hands. Because of that decision, and his willingness to stand for others, the killer was stopped.
There will be those who claim it was irrelevant, that the killer had done his business in the church, but they forget that it seems likely the church itself wasn’t his target. It was the mother-in-law who was a member there.
Who else could have died because this made has family issues?
Thanks to Stephen Willeford, we won’t actually know.
Massachusetts Enacts Bump Fire Stock Ban: Possible Life Imprisonment for Simple Possession
“Massachusetts became the first state to enact a ban on bump stocks following the mass shooting at a Las Vegas music festival,” foxnews.com reports. “Republican Lt. Gov. Karyn Polito signed the bill Friday in her capacity as acting governor because Republican Gov. Charlie Baker is on vacation in California.” The bill’s penalties are beyond harsh . . .
“The provision passed by the legislature allows for excessive punishment including life imprisonment,” The Gun Owners Action League of Massachusetts (GOAL) warned ahead of Polito’s signature, “with a minimum sentence of 18 months, for the mere possession of these accessories.”
The ban — tucked away in a “mini” appropriations bill — gives Bay Staters 90 days to get rid of their bump fire stocks. Not sell. Eliminate. “The legislation was passed leaving no pathway to legal ownership. It also makes it illegal for owners of these items to legally sell them,” GOAL points out. Fifth Amendment that.
Meanwhile, the bill’s supporters are busy using the immediate aftermath of its passage to trumpet the benefits of banning a device which has been used in precisely no crimes in their state.
Democratic state Rep. David Linsky, one of the first in Massachusetts to call for outlawing the devices, said it would make the state safer while respecting the rights of gun owners.
“I am proud of my colleagues in the Legislature for continuing Massachusetts’ reputation as having among the safest and most effective gun laws in the nation,” he said.
While the Nest would beat it in a beauty contest, this Sensi thermostat has most of the same smart features in a more traditional body, and it’s a hell of a lot cheaper.
One of the most notable of those smart features is Alexa support; if there’s an Amazon Echo in range, you can change your home’s temperature with nothing but your voice. For a limited time, you can get the Sensi and an Echo Dot for just $108, which is $71 less than buying them separately, and somewhat incredibly, $21 less than buying the thermostat by itself.
Blizzard is taking StarCraft 2: Wings of Liberty‘s campaign free to play. As Polygon reports, come November 14th, you’ll have access to the entire narrative and if you already own that, you’ll get the Protoss-themed Heart of the Swarm campaign for free. The other narratives will run you $15 each. Unlike StarCraft II: Starter Edition that included free multiplayer, the adversarial mode that comes in tow here will feature ranked play — not just casual, unranked matches.
It’s a smart move, and free access to ranked multiplayer could be a boon for the StarCraft eSports scene. After all, Dota 2 and League of Legends are both free-to-play (as is Blizzard’s own Heroes of the Storm), and those are doing pretty well for themselves. Valve saw a sizable uptick in players — and money — after making the aging Team Fortress 2 free-to-play, as well.
