Re: Horrible ftruncate performance

[Szakacsits Szabolcs <szaka@sienet.hu>]

Hi,

On Thu, 10 Jul 2003, Oleg Drokin wrote:

> May be this is because when system time was very big, the difference
> looked like a noise? ;)

You can decide yourself,

PIII/666:  0.00s  usr,  917.83s sys   923.72s real,  99% CPU
Xeon/1.7:  0.00s  usr,  862.79s sys,  865.13s real,  99% CPU

> > Yes, I have whatever the latest distros ship. Right now I could check out
> > only Red Hat 9 and SuSE 8.2, they both have 3.6.4. The latest reiserfsprogs
> > is 3.6.8.
>
> Actually 3.6.4 has support for blocksizes other than 4k, this is
> controlled by -b switch of mkreiserfs (run it without arguments and it
> will tell you) man page on mkreiserfs (in SuSE 8.2 at least) have it
> listed too.

Both SuSE 8.2 and Red Hat 9 mkreiserfs manual say:

       -b | --block-size N
              N is block size in bytes. 4096 only for now.

> The 4k blocksize is not FS limit, this is VFS limit related to the fact
> that buffer size cannot be bigger than PAGE_SIZE.

Yes but people aren't really interested in this. FreeBSD uses 8 kB for at
least about 6 years by default and NTFS max 64 kB for a decade (frequently
used in benchmarks and when high performance is needed and make sense).

If today I take a stock kernel, which main Linux filesystems support bigger
than 4 kB block size? None.

> Also there is an effort by William Lee Irwin III to create "clustered
> page cache" or something like that (the patchset is named

I know, also it's too late for 2.6.

	Szaka