Messages in this thread | | | Subject | Re: spinlock contention of files->file_lock | From | Eric Dumazet <> | Date | Mon, 30 Sep 2013 19:18:53 -0700 |
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On Mon, 2013-09-30 at 18:44 -0700, Linus Torvalds wrote: > On Mon, Sep 30, 2013 at 6:05 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote: > > Speaking of spinlock contention, the files->file_lock is a good example. > > > > Multi threaded programs hit this spinlock three times per fd : > > .. do you actually have programs that see contention?
Yes, Google-Bug-Id 9072743 for Googlers ;)
Basically, we have (many) servers with 10,000,000+ sockets, where this lock contention is a real problem.
We use a SOCK_FD_FASTALLOC accept4()/socket() flag to relax POSIX requirements and not having to parse huge bitmap in find_next_zero_bit(fdt->open_fds, fdt->max_fds, fd) (O_FD_FASTALLOC uses a random starting point)
I am writing a patch using cmpxchg() to see if I can solve the dup2() 'problem'
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