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SubjectRe: [PATCH resend] drop_caches: add some documentation and info message
On Tue 30-07-13 01:25:44, Andrew Morton wrote:
> On Tue, 30 Jul 2013 09:45:31 +0200 Michal Hocko <mhocko@suse.cz> wrote:
>
> > On Mon 29-07-13 13:57:43, Andrew Morton wrote:
> > > On Fri, 26 Jul 2013 14:44:29 +0200 Michal Hocko <mhocko@suse.cz> wrote:
> > [...]
> > > > --- a/fs/drop_caches.c
> > > > +++ b/fs/drop_caches.c
> > > > @@ -59,6 +59,8 @@ int drop_caches_sysctl_handler(ctl_table *table, int write,
> > > > if (ret)
> > > > return ret;
> > > > if (write) {
> > > > + printk(KERN_INFO "%s (%d): dropped kernel caches: %d\n",
> > > > + current->comm, task_pid_nr(current), sysctl_drop_caches);
> > > > if (sysctl_drop_caches & 1)
> > > > iterate_supers(drop_pagecache_sb, NULL);
> > > > if (sysctl_drop_caches & 2)
> > >
> > > How about we do
> > >
> > > if (!(sysctl_drop_caches & 4))
> > > printk(....)
> > >
> > > so people can turn it off if it's causing problems?
> >
> > I am OK with that but can we use a top bit instead. Maybe we never have
> > other entities to drop in the future but it would be better to have a room for them
> > just in case.
>
> If we add another flag in the future it can use bit 3?

What if we get crazy and need more of them?

> > So what about using 1<<31 instead?
>
> Could, but negative (or is it positive?) numbers are a bit of a pain.

Yes, that was the point ;), I would like to make a new usage a dance on
the meadows.
But I do not care much, let's use 1<<30 if negative sounds too bad but I
would leave some room for further entities.

--
Michal Hocko
SUSE Labs


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