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    SubjectRe: [PATCH v7 1/4] spinlock: A new lockref structure for lockless update of refcount
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    On Sun, Sep 1, 2013 at 3:44 PM, Al Viro <viro@zeniv.linux.org.uk> wrote:
    >
    > GRRR... I see something else:
    > void file_sb_list_del(struct file *file)
    > {
    > if (!list_empty(&file->f_u.fu_list)) {
    > lg_local_lock_cpu(&files_lglock, file_list_cpu(file));
    > list_del_init(&file->f_u.fu_list);
    > lg_local_unlock_cpu(&files_lglock, file_list_cpu(file));
    > }
    > }
    > will cheerfully cause cross-CPU traffic. If that's what is going on, the
    > earlier patch I've sent (not putting non-regulars and files opened r/o
    > on ->s_list) should reduce the cacheline bouncing on that cacheline.

    Hmm. That might indeed be a bad sources of cross-cpu bouncing on some
    loads, but the load I test doesn't actually open any files. It just
    does "stat()" on a filename.

    So no "struct file *" anywhere for me..It really seems to be
    vfsmount_lock itself somehow.

    Linus


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