11–20 of 106 posts
Is there any particular reason why Oracle DBAs are less likely to believe this? Perhaps it's because most of them grew up in legacy UNIX environments rather than Linux.
I've tried to educate Oracle DBAs on why top is wrong and their memory really isn't being used. It's painful and they often refuse to believe that I know what I'm talking about, and that they should use the free -m command to see what memory is actually available for use. Is there any particular reason why Oracle DBAs are less likely to believe this? Perhaps it's because most of them grew up in legacy UNIX environmen…
The cache can be cleared via `/proc/sys/vm/drop_caches`. http://linux-mm.org/Drop_Caches
There are very good reasons that Linux (and most other modern operating systems) makes aggressive use of page caches and buffers. For the vast majority of applications dropping these caches is going to reduce performance considerably (disk is really really slow) and most applications for which this isn't true are probably using O_DIRECT anyway.
The arguments in favor of page caching are: (a) disks have very high latency (b) disks have relatively low bandwidth (c) for hot data RAM is cheaper disk IO both in dollars and in watts [1] and (d) it's basically free because the memory would have been unused anyway.
The arguments against page caching are: (a) occasionally the kernel will make poor choices and do something sub-optimal and (b) high numbers in 'free' make me feel better.
Too many inexperienced operators (or those experienced on other OSs) confuse disadvantage (a) for disadvantage (b) and decide to drop caches using a cron job.
[1] Old but good: ftp://ftp.research.microsoft.com/pub/tr/tr-97-33.pdf
http://webcache.googleusercontent.com/search?q=cache:http://... http://webcache.googleusercontent.com/search?q=cache:http://...
Earlier quoted context omitted.
People say the same things on Mac: http://news.ycombinator.com/item?id=3584609 It represents a fundamental misunderstanding of how modern OSes work. That misunderstanding is not the problem; modern OSes are complex pieces of software, and most people shouldn't have to understand them. OSes should just work. The problem comes in when people who don't understand how they work get the itch to "improve" their system.
I'm actually continually amazed that even some technically inclined people misunderstand how memory works in /all/ modern OSes: recently I had a discussion on Twitter that went something like this: "OS X is horrible, it uses nearly all of my 8 gigs of RAM and my browser is horribly slow!" to which I replied, "it's perfectly normal for the OS to appropriate the RAM in the fashion you see in Activity Monitor; this does…
Earlier quoted context omitted.
People say the same things on Mac: http://news.ycombinator.com/item?id=3584609 It represents a fundamental misunderstanding of how modern OSes work. That misunderstanding is not the problem; modern OSes are complex pieces of software, and most people shouldn't have to understand them. OSes should just work. The problem comes in when people who don't understand how they work get the itch to "improve" their system.
Programmers need to remember that users are like this: (from an Apple discussion thread) … [periodically]'installd' begins using 100% of all 4 CPU cores, my fan goes full speed and the whole computer gets very hot. Seems to happen before Software Update checks for updates. I usually go to the terminal and kill the 'installd' process, which reduces the fan speed and heat to normal within a minute. I wonder if this guy…
firefoxatemyram.com is still available. Perhaps we can put a site up there as well.
Linux just looks like it ate your RAM. Firefox straight up does eat it.
I've tried to educate Oracle DBAs on why top is wrong and their memory really isn't being used. It's painful and they often refuse to believe that I know what I'm talking about, and that they should use the free -m command to see what memory is actually available for use. Is there any particular reason why Oracle DBAs are less likely to believe this? Perhaps it's because most of them grew up in legacy UNIX environmen…
I've tried to educate Oracle DBAs on why top is wrong and their memory really isn't being used. It's painful and they often refuse to believe that I know what I'm talking about, and that they should use the free -m command to see what memory is actually available for use. Is there any particular reason why Oracle DBAs are less likely to believe this? Perhaps it's because most of them grew up in legacy UNIX environmen…
2nd is explaining virtual/resident set size.
Earlier quoted context omitted.
People say the same things on Mac: http://news.ycombinator.com/item?id=3584609 It represents a fundamental misunderstanding of how modern OSes work. That misunderstanding is not the problem; modern OSes are complex pieces of software, and most people shouldn't have to understand them. OSes should just work. The problem comes in when people who don't understand how they work get the itch to "improve" their system.
Programmers need to remember that users are like this: (from an Apple discussion thread) … [periodically]'installd' begins using 100% of all 4 CPU cores, my fan goes full speed and the whole computer gets very hot. Seems to happen before Software Update checks for updates. I usually go to the terminal and kill the 'installd' process, which reduces the fan speed and heat to normal within a minute. I wonder if this guy…
Ubuntu had or has the same issue with a deamon used for the graphical package-administrations-guis rebuilding an index (I forgot the name). They tried to help themselves with appropriate nice-settings, defused the issue, but on old machines you still need to move the cronjob to monthly to have a usable system.
You simply can't use the system properly when a background-process uses all ressources. And one normally want do something else than wait for the system. I consider such behaviour a bug.