On Wed, 2012-08-22 at 11:38 -0500, Nathan Zimmer wrote:
> This moves a kfree outside a spinlock to help scaling on larger (512 core)
> systems.
>
> I ran a simple test which just reads from /proc/cpuinfo.
> Lower is better, as you can see the worst case scenario is improved.
>
> baseline moved kfree
> tasks read-sec read-sec
> 1 0.0141 0.0141
> 2 0.0140 0.0140
> 4 0.0140 0.0141
> 8 0.0145 0.0145
> 16 0.0553 0.0548
> 32 0.1688 0.1622
> 64 0.5017 0.3856
> 128 1.7005 0.9710
> 256 5.2513 2.6519
> 512 8.0529 6.2976
>
> Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
> Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
> Acked-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>
> Signed-off-by: Nathan Zimmer <nzimmer@xxxxxxx>
> ---
> fs/proc/inode.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/fs/proc/inode.c b/fs/proc/inode.c
> index 7ac817b..bf36266 100644
> --- a/fs/proc/inode.c
> +++ b/fs/proc/inode.c
> @@ -403,9 +403,9 @@ static int proc_reg_release(struct inode *inode, struct file *file)
> release = pde->proc_fops->release;
> if (pdeo) {
> list_del(&pdeo->lh);
> - kfree(pdeo);
> }
> spin_unlock(&pde->pde_unload_lock);
> + kfree(pdeo);
>
> if (release)
> rv = release(inode, file);
Thats interesting, but if you really want this to fly, one RCU
conversion would be much better ;)
pde_users would be an atomic_t and you would avoid the spinlock
contention.
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