[RFC PATCH v9 0/8] [PIDNS] Final

[Dmitry V. Levin]

On Wed, Aug 19, 2020 at 12:37:14AM +0200, Ákos Uzonyi wrote:
> On Tue, 18 Aug 2020 at 01:38, Dmitry V. Levin <ldv at altlinux.org> wrote:
> > On Mon, Aug 17, 2020 at 12:18:43AM +0200, Ákos Uzonyi wrote:
> > > From: Uzonyi Ákos <uzonyi.akos at gmail.com>
> > >
> > > I made the requested changes, added more test cases to trie test, and fixed some
> > > trie bugs.
> > >
> > > The travis build [1] unfortunately shows some errors. On ppc mknod test fails,
> > > but I have no idea why. Mknod is unrelated to my code. Do you have any idea?
> >
> > Something is broken in their ppc system: apparently, they allow the mknod
> > syscall to exit without an error in cases where is must fail with EEXIST
> > because the target file already exists.  This violates the contract:
> > "If pathname already exists, or is a symbolic link, this call fails with
> > an EEXIST error."  I suppose they use some kind of mknod interception,
> > and it doesn't implement the expected semantics.
> >
> > We can either come up with a workaround or report a bug and let them fix it.
> 
> What seems really strange is that only the last two mknod does not
> fail with EEXIST.

Only the last two mknod calls are trying to create devices,
all the rest aren't.  This looks like an error in some seccomp filter.

> > > Also, pidns-cache fails on one arm build. I tried to increase the time
> > > available for translation, but it didn't help.
> >
> > Could you add some diagnostics to the test, e.g. how much time did it take
> > in the first and in the second case?  This way we could see what's going
> > on.
> 
> Here are the results:
> (no translation | translation with cache | translation without cache)
> 
> the 3 arm builds:
> 17846us   76435us   3676880us
> 141378us  496301us  3379754us
> 8699us    134754us  2974909us
> 
> on my system:
> 948us     9358us    916094us

I wonder why the cached translation takes that long on your system:
9358 / 948 ≈ 10

Would it make sense to increase SYSCALL_COUNT so that cache effect would
become more visible compared to the translation without cache?


-- 
ldv