linux-kernel - Re: [PATCH] namei: Remove unlikely annotation for revalidate check in lookup

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Message-ID: <20170207000642.GH13195@ZenIV.linux.org.uk>
Date:   Tue, 7 Feb 2017 00:06:42 +0000
From:   Al Viro <viro@...IV.linux.org.uk>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] namei: Remove unlikely annotation for revalidate check
 in lookup_fast()

On Mon, Feb 06, 2017 at 05:17:35PM -0500, Steven Rostedt wrote:
> From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>
> 
> The likely/unlikely profiler showed that the unlikely around the
> dentry->d_flags & DCACHE_OP_REVALIDATE was wrong 95% of the time. Adding
> trace_printk()s, it revealed that the dentry ops had hooks to:
> 
>  kernfs_dop_revalidate
>  pid_revalidate
>  proc_sys_revalidate
>  tid_fd_revalidate
> 
> As tools today now access files that have these operations often, it's best
> just to remove the annotation, as it is more dependent on use cases and not
> normal mode of operation if it will be true or not.

"Tools" being what, exactly?  What kind of load had that been measured on?