On Fri, 26 Jul 2013 14:44:29 +0200 Michal Hocko <mhocko@xxxxxxx> wrote:
> ...
>
> : There is plenty of anecdotal evidence and a load of blog posts
> : suggesting that using "drop_caches" periodically keeps your system
> : running in "tip top shape". Perhaps adding some kernel
> : documentation will increase the amount of accurate data on its use.
> :
> : If we are not shrinking caches effectively, then we have real bugs.
> : Using drop_caches will simply mask the bugs and make them harder
> : to find, but certainly does not fix them, nor is it an appropriate
> : "workaround" to limit the size of the caches.
> :
> : It's a great debugging tool, and is really handy for doing things
> : like repeatable benchmark runs. So, add a bit more documentation
> : about it, and add a little KERN_NOTICE. It should help developers
> : who are chasing down reclaim-related bugs.
>
> ...
>
> --- 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?
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