proc: spread likely/unlikely a bit (15b158b4) · Commits · 戴 / test

use_pde() is used at every open/read/write/... of every random /proc file. Negative refcount happens only if PDE is being deleted by module (read: never). So it gets "likely". unuse_pde() gets "unlikely" for the same reason. close_pdeo() gets unlikely as the completion is filled only if there is a race between PDE removal and close() (read: never ever). It even saves code on x86_64 defconfig: add/remove: 0/0 grow/shrink: 1/2 up/down: 2/-20 (-18) Function old new delta close_pdeo 183 185 +2 proc_reg_get_unmapped_area 119 111 -8 proc_reg_poll 85 73 -12 Link: http://lkml.kernel.org/r/20180104175657.GA5204@avx2 Signed-off-by:

Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

fs/proc/inode.c

+4 −4

Original line number	Diff line number	Diff line
		@@ -129,12 +129,12 @@ enum {BIAS = -1U<<31};

		static inline int use_pde(struct proc_dir_entry *pde)
		{
		return atomic_inc_unless_negative(&pde->in_use);
		return likely(atomic_inc_unless_negative(&pde->in_use));
		}

		static void unuse_pde(struct proc_dir_entry *pde)
		{
		if (atomic_dec_return(&pde->in_use) == BIAS)
		if (unlikely(atomic_dec_return(&pde->in_use) == BIAS))
		complete(pde->pde_unload_completion);
		}

		@@ -167,7 +167,7 @@ static void close_pdeo(struct proc_dir_entry pde, struct pde_opener pdeo)
		spin_lock(&pde->pde_unload_lock);
		/* After ->release. */
		list_del(&pdeo->lh);
		if (pdeo->c)
		if (unlikely(pdeo->c))
		complete(pdeo->c);
		kfree(pdeo);
		}
		@@ -421,7 +421,7 @@ static const char proc_get_link(struct dentry dentry,
		struct delayed_call *done)
		{
		struct proc_dir_entry *pde = PDE(inode);
		if (unlikely(!use_pde(pde)))
		if (!use_pde(pde))
		return ERR_PTR(-EINVAL);
		set_delayed_call(done, proc_put_link, pde);
		return pde->data;

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