On Wed, Oct 27, 2010 at 11:05 AM, Rik van Riel <riel@xxxxxxxxxx> wrote:
On 10/27/2010 01:21 PM, Ying Han wrote:The reasoning behind the patch makes sense.
kswapd's use case of hardware PTE accessed bit is to approximate page LRU. The
ActiveLRU demotion to InactiveLRU are not base on accessed bit, while it is only
used to promote when a page is on inactive LRU list. All of the state transitions
are triggered by memory pressure and thus has weak relationship with respect to
time. In addition, hardware already transparently flush tlb whenever CPU context
switch processes and given limited hardware TLB resource, the time period in
which a page is accessed but not yet propagated to struct page is very small
in practice. With the nature of approximation, kernel really don't need to flush TLB
for changing PTE's access bit. This commit removes the flush operation from it.
Signed-off-by: Ying Han<yinghan@xxxxxxxxxx>
Singed-off-by: Ken Chen<kenchen@xxxxxxxxxx>
However, have you measured any improvements in run time with
this patch? The VM is already tweaked to minimize the number
of pages that get aged, so it would be interesting to know
where you saw issues.
Rik, the workload we were running are some MapReduce jobs.
--Ying
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