On Mon, Jan 07, 2019 at 11:25:16AM -0800, Dave Hansen wrote:
> On 1/7/19 6:15 AM, Matthew Wilcox wrote:
> > You're going to get data corruption doing this. try_to_unmap_one()
> > does:
> >
> > /* Move the dirty bit to the page. Now the pte is gone. */
> > if (pte_dirty(pteval))
On 1/7/19 6:15 AM, Matthew Wilcox wrote:
> You're going to get data corruption doing this. try_to_unmap_one()
> does:
>
> /* Move the dirty bit to the page. Now the pte is gone. */
> if (pte_dirty(pteval))
> set_page_dirty(page);
>
> so PageDirty() can be false
On Mon, Jan 07, 2019 at 02:02:39PM +0100, Vincent Whitchurch wrote:
> +++ b/Documentation/sysctl/vm.txt
> @@ -222,6 +222,10 @@ To increase the number of objects freed by this
> operation, the user may run
> number of dirty objects on the system and create more candidates to be
> dropped.
>
> +
drop_caches does not drop pages which are currently mapped. Add an
option to try to unmap and drop even these pages. This provides a
simple way to obtain a rough estimate of how many file pages are used in
a particular use case: drop everything and check how much gets read
back.
# cat /proc/mem
