Dipankar Sarma <[email protected]> writes:
>
> I should add that this is a general trend we see in all workloads
> that do a lot of open/closes and so much so that performance is very
> sensitive to how close to / your application's working directory
> is. You would get much better system time if you compile a kernel
> in /linux as compared to say /home/fs01/users/akpm/kernel/linux ;-)
That's interesting. Perhaps it would make sense to have a fast path
that just does a string match of the to be looked up path to a cached copy
of cwd and if it matches works as if cwd was the root. Would need to be
careful with chroot where cwd could be outside the root and clear the
cached copy in this case. Then you could avoid all the locking overhead
for directories above your cwd if you stay in there.
-Andi
On Sat, Nov 02, 2002 at 11:08:44AM +0100, Andi Kleen wrote:
> Dipankar Sarma <[email protected]> writes:
> >
> > I should add that this is a general trend we see in all workloads
> > that do a lot of open/closes and so much so that performance is very
> > sensitive to how close to / your application's working directory
> > is. You would get much better system time if you compile a kernel
> > in /linux as compared to say /home/fs01/users/akpm/kernel/linux ;-)
>
> That's interesting. Perhaps it would make sense to have a fast path
> that just does a string match of the to be looked up path to a cached copy
> of cwd and if it matches works as if cwd was the root. Would need to be
> careful with chroot where cwd could be outside the root and clear the
> cached copy in this case. Then you could avoid all the locking overhead
> for directories above your cwd if you stay in there.
Well, on second thoughts I can't see why the path length for pwd
would make difference for kernel compilation - it uses relative
path and for path lookup, if the first character is not '/', then
lookup is done relative to current->fs->pwd. I will do some more
benchmarking on and verify.
I did get inputs from Troy Wilson who does specweb measurements
that the path name length of the location of the served files
make a difference. I presume his webserver setup used full path names.
Thanks
Dipankar
> Well, on second thoughts I can't see why the path length for pwd
> would make difference for kernel compilation - it uses relative
> path and for path lookup, if the first character is not '/', then
> lookup is done relative to current->fs->pwd. I will do some more
> benchmarking on and verify.
Kernel compilation actually uses absolute pathnames e.g. for dependency
checking. TOPDIR is also specified absolutely, so an include access likely
uses an absolute pathname too.
-Andi