Re: [RFC 1/3] procfs: fdinfo -- Extend information about epoll target files

From	Cyrill Gorcunov <gorcunov@gmail.com>
Newsgroups	linux.kernel
Subject	Re: [RFC 1/3] procfs: fdinfo -- Extend information about epoll target files
Date	2017-02-22 09:00 +0100
Message-ID	<tdA09-6IQ-9@gated-at.bofh.it> (permalink)
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On Wed, Feb 22, 2017 at 10:44:07AM +0300, Pavel Emelyanov wrote:
> On 02/21/2017 10:16 PM, Cyrill Gorcunov wrote:
> > On Tue, Feb 21, 2017 at 10:41:12AM -0800, Andy Lutomirski wrote:
> >>> Thus lets add file position, inode and device number where
> >>> this target lays. This three fields can be used as a primary
> >>> key for sorting, and together with kcmp help CRIU can find
> >>> out an exact file target (from the whole set of processes
> >>> being checkpointed).
> >>
> >> I have no problem with this, but I'm wondering whether kcmp's ordered
> >> comparisons could also be used for this purpose.
> > 
> > Yes it can, but it would increas number of kcmp calls signisicantly.
> 
> Actually it shouldn't. If you extend the kcmp argument to accept the
> epollfd:epollslot pair, this would be effectively the same as if you
> had all your epoll-ed files injected into your fdtable with "strange"
> fd numbers. We already have two-level rbtree for this in criu, adding
> extended ("strange") fd to it should be OK.

Nope. Pavel, I guess you forget how we handle file tree in criu currently.
We call for kcmp only if we have to -- when primary key for two entries
is the same.

Thread

[RFC 1/3] procfs: fdinfo -- Extend information about epoll target files Cyrill Gorcunov <gorcunov@openvz.org> - 2017-02-21 18:20 +0100
  Re: [RFC 1/3] procfs: fdinfo -- Extend information about epoll target files Andy Lutomirski <luto@amacapital.net> - 2017-02-21 19:50 +0100
    Re: [RFC 1/3] procfs: fdinfo -- Extend information about epoll  target files Cyrill Gorcunov <gorcunov@gmail.com> - 2017-02-21 20:20 +0100
      Re: [RFC 1/3] procfs: fdinfo -- Extend information about epoll  target files Cyrill Gorcunov <gorcunov@gmail.com> - 2017-02-22 09:00 +0100
        Re: [RFC 1/3] procfs: fdinfo -- Extend information about epoll  target files Cyrill Gorcunov <gorcunov@gmail.com> - 2017-02-22 09:20 +0100
          Re: [RFC 1/3] procfs: fdinfo -- Extend information about epoll  target files Cyrill Gorcunov <gorcunov@gmail.com> - 2017-02-22 09:40 +0100

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