Thread: linux writing often on main disk

(2) Is my argument about NPTL vs. linuxthreads correct?

Yes.

(1) Is his argument about linux writing often to main file system correct?

I don't think any standard linux distro writes to disk more often than any other linux.

re: linux writing to disk: I read a little while ago that because linux, like all *nix, maintains "access times" for the filesystem, this means every disk read must also be complimented by a disk WRITE in order to update the atime. Supposedly all this adds up, so in heavy use situations where the atime is not considered crucial (since the m(odification)time is seperate from the atime, you might wonder when it ever would really be important) you can start linux with the "noatime" kernel parameter which means the kernel no longer writes an atime to disk every time a file is accessed. And this means something like a 10-20% improvement in speed where the disk access is constant.

Since you are dealing with significance on the order of 25ms and are worried about time wasted with (basically irrelevent) writes to disk, I thot I'd mention that. Google "noatime" and some articles will appear.

Originally Posted by mynickmynick

But I remember I made some tests on Debian with RAMdisk and I found out that the time for writing to ramdisk was only 20% less than writing on hard disk

That just means Linux's filesystem caching is about 80% efficient.

Yes, Linux is generally using any spare memory (memory that isn't currently used by applications or the kernel itself) as a cache for disk operations, so writing to disk will actually just write to memory, and later on write to disk proper.

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Mats