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List:       linux-fsdevel
Subject:    Re: [PATCH] vfs: Add a trace point in the mark_inode_dirty function
From:       KOSAKI Motohiro <kosaki.motohiro () jp ! fujitsu ! com>
Date:       2010-11-30 0:37:30
Message-ID: 20101130093450.82DD.A69D9226 () jp ! fujitsu ! com
[Download RAW message or body]

> Yes, this came up before. Currently, if you add the if statement in the
> trcacepoint, you just wasted space. But if we can add a discard_entry,
> or better yet, I can add a TRACE_EVENT_CONDITION() that adds an if
> statement to check. Something like:
> 
> 	TRACE_EVENT_CONDITION(name,
> 		[...]
> 	TP_condition(
> 			if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC |
> 			    I_DIRTY_PAGES))
> 				return 1;
> 			else
> 				return 0;
> 		    ),

I love this idea. :)

For MM, struct page has a lot of union hack. then, page tracer strongly need conditional
trace point.


> 
> Have this run on the parameters and not the entry fields (because the
> entry fields are from the ring buffer, and to use them, we must first
> write to the ring buffer (something we want to avoid).
> 
> We could also make this code work with "pre-filters". That is, filters
> on the tracepoints that access the parameters and not the final entries.
> This would let us circumvent allocating ring buffer space when the
> filter states to skip the entry.
> 
> -- Steve
> 
> 			
> 
> 



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