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Use dd to read a section of a file without reading everything preceding it.  For your example (reading bytes 4,120,000-4,120,400) you could use dd bs=400 skip=10300 count=1 if=your_input_file of=your_output_file This defines a logical block size of 400 bytes, and then tells dd to skip the first 10300 “logical blocks” of the input file (if).  10300 is ...


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The linux kernel does cache management automatically. Everthing that is loaded into RAM, stays there until another process needs RAM and there is no more available. So in the linux kernel RAM should always be full. You system has 128GB of RAM, thats more than enough for a 100-1000MB file. To load a huge file into RAM just cat it: cat huge_file > ...


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Is there a way to make it read those files faster? Yes: Replace HDD with SSD. No problem with seek times then :) Have you tried using preload ? You might want to read drawbacks of using preload also. Maybe there is a tool to move the blocks of files to consecutive sectors ? There's Accelerated Knoppix which can do this for a CD image, but ...


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What is the output of the following? glxinfo | grep "direct rendering" You need the mesa-utils package installed to get glxinfo. Debian jessie should have a new enough kernel (3.14) to support Haswell, I think the issue with lacking 3D acceleration was only on wheezy. If you get "direct rendering: Yes", we can continue from there, but if direct rendering ...


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You wrote: It surprises me to see find iterate/walk through the complete filesystem when I do a simple find -inum 12345 find, by definition, does a tree walk starting at the given directory or directories, with a default starting directory of .. find -inum 12345 will walk through the entire directory tree starting with the current working directory. ...


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Instead of bothering with this wasteful approach why not setup an ipset instead. A set of IPs can be matched to a single firewall entry rather than having to maintain 3500 entries. IP sets Here's a good intro/tutorial on how to use them in this Linux Journal article titled: Advanced Firewall Configurations with ipset. Example Setup a set to contain ...


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The very simple reason is that at least for the ext2/ext3/ext4 type filesystems the filenames are stored via the directory entries data stored in directory type files. This means that those files that are from type directory have a more or less intricate system to store filenames (of the files inside of the directory) and the inodes which lead to the data ...


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UNIX has three syscalls: lstat(),fstat(),stat() All of these system calls return a stat structure, which contains the following fields: struct stat { dev_t st_dev; /* ID of device containing file */ ino_t st_ino; /* inode number */ mode_t st_mode; /* protection */ nlink_t st_nlink; /* number of ...


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If you're going to run all the threads on one core, buy cheaper hardware with a single core. The scheduler tries to make maximum use of all the cores. This means dispatching threads to whatever core has some free time. Moving a thread from one core to another core has a small cost, so the scheduler does try to avoid this. But you'll typically not notice it ...


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No. ionice is a mechanism for specifying priorities. But deadline ignores priorities and instead simply imposes an expiration time on each I/O operation and then ensures that the operation succeeds before the expiration time is met. More information here: Deadline Scheduling: coming soon? To recap briefly: deadline scheduling does away with the concept ...


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Depends on your application, doesn't it? I think you should have some swap space, perhaps even as small as half the RAM size. You don't want your system to choke.


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I don't think that huge pages are worth the trouble on a typical desktop use. Data in huge pages is very slightly faster to access, but this requires allocating memory in chunks of 2MB at a time (on x86_64, with similar sizes on other architectures). Most applications allocate memory in far smaller chunks. The two main applications of huge pages in user ...


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Most terminal emulators will not render all the text when there's a lot of output in a short time; they will skip data to save time. E.g. rxvt has the -ss option for "skip scrolling" (multiple screens per refresh) and -j for "jump scrolling" (multiple lines per refresh).



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