Re: Solved: 1.3.94: open () still slower than 1.2.13
Dr. Werner Fink (werner@suse.de)
Tue, 30 Apr 1996 23:18:59 +0200
> Date: Fri, 26 Apr 1996 15:47:43 +0300 (EET DST)
> From: Linus Torvalds <torvalds@cs.helsinki.fi>
>
> On Thu, 25 Apr 1996, Pete Harlan wrote:
> >
> > > How much memory to you have ?
> > > Are you sure that everything is cached ?
> > >
> > > With 1.2.x, your 5517 files will use 5517*2k=11034k
> > > With the latest 1.3.x, they will use 5517*4k=22068k...
> >
> > That was it! Many, many thanks. I reran my tests with 2,800 files
> > and 1.3.94 was a weency bit faster than 1.2.13.
>
> Yes, this is a pretty real problem with the new page cache: the
> "allocation block" for the cache is larger than before, and as such the
> page cache can be slower than it used to be under 1.2.x.
>
> I'm afraid that is inevitable - there is a tradeoff here, and overall the
> page cache is so much cleaner than the old buffer cache that I'm not
> looking back (especially as most of my machines have indecent amounts of
> RAM in them considering how much I actually would need).
>
> This is a real problem for development, actually - most of the people
> who test out the development kernels have reasonably high-end hardware,
> if only because on low-end hardware it can take longer to compile a
> kernel than it takes for me to release a new one ;-). Anyway, that kind
> of leads to the kernels getting much more testing on high-end machines. I
> hope we're still usable on a 4MB machine ;-/
>
> Linus
Is there an easy way to make the amount of the "allocation block" depend on
the amount of the pysical memory and/or swap space?
Werner