Re: [PATCH RESEND] mm: trace filemap add and del

[Andrew Morton <akpm@linux-foundation.org>]

On Thu, 28 Feb 2013 21:47:00 +0100
Robert Jarzmik <robert.jarzmik@free.fr> wrote:

> Use the events API to trace filemap loading and unloading of file pieces
> into the page cache.
> 
> This patch aims at tracing the eviction reload cycle of executable and
> shared libraries pages in a memory constrained environment.
> 
> The typical usage is to spot a specific device and inode (for example
> /lib/libc.so) to see the eviction cycles, and find out if frequently used
> code is rather spread across many pages (bad) or coallesced (good).
> 
> ...
>
>  		if (likely(!error)) {
>  			mapping->nrpages++;
>  			__inc_zone_page_state(page, NR_FILE_PAGES);
> +			trace_mm_filemap_add_to_page_cache(page);
>  			spin_unlock_irq(&mapping->tree_lock);
>  		} else {
>  			page->mapping = NULL;

I don't see a need to do this under the spinlock.  The page is locked
so nobody else will be fiddling with it.  There would be a tiny
scalability gain from moving the tracepoint outside the locked region.


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