Re: [PATCH 0/1] pagemap clear_refs: modify to specify anon or mappedvma clearing

[Moussa A. Ba]

Matt Mackall wrote:
> On Thu, 2009-07-23 at 20:56 -0700, Moussa A. Ba wrote:
> > This patch makes the clear_refs proc interface a bit more versatile. It 
> > adds support for clearing either anonymous, file mapped pages or both.
> >
> > echo 1 > /proc/pid/clear_refs clears ANON pages
> > echo 2 > /proc/pid/clear_refs clears file mapped pages
> > echo 3 > /proc/pid/clear_refs clears all pages
> >
> > Selectively clearing pages has a measurable impact on performance as it 
> > decreases the number of page walks.  We have been using this interface 
> > and this adds flexibility to the user space application implementing the 
> > reference clearing.
>
> [adding David, the original instigator of clear_refs)
>
> First, don't send 0 of 1 messages, especially for a single patch. It
> makes Andrew curse and makes him more likely to consider other
> employment possibilities. Instead incorporate highly useful info like
> the above into your patch instead, preferably as docs and commit
> descriptions.
>
> Second, depending on how we've documented the behavior of this file,
> this looks like it might break existing tools that are currently writing
> '1' but expecting the behavior of '3'?

Thank you for the kind advice, I was afraid of that...  In regards to 
the behavior of 1 vs 3, this had indeed occurred to us, and it was a 
tossup.  I was hoping to get feedback first before deciding which way to 
go.  However, it does seem like a better idea to go with the default 
behavior when writing '1' and the special behaviors for 2 and 3.


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/