Messages in this thread | | | Date | Thu, 10 Nov 2011 16:29:44 +0100 | From | Johannes Weiner <> | Subject | Re: [rfc 1/3] mm: vmscan: never swap under low memory pressure |
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On Mon, Nov 07, 2011 at 11:29:41AM +0900, KAMEZAWA Hiroyuki wrote: > On Wed, 2 Nov 2011 17:31:41 +0100 > Johannes Weiner <jweiner@redhat.com> wrote: > > > We want to prevent floods of used-once file cache pushing us to swap > > out anonymous pages. Never swap under a certain priority level. The > > availability of used-once cache pages should prevent us from reaching > > that threshold. > > > > This is needed because subsequent patches will revert some of the > > mechanisms that tried to prefer file over anon, and this should not > > result in more eager swapping again. > > > > It might also be better to keep the aging machinery going and just not > > swap, rather than staying away from anonymous pages in the first place > > and having less useful age information at the time of swapout. > > > > Signed-off-by: Johannes Weiner <jweiner@redhat.com> > > --- > > mm/vmscan.c | 2 ++ > > 1 files changed, 2 insertions(+), 0 deletions(-) > > > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > index a90c603..39d3da3 100644 > > --- a/mm/vmscan.c > > +++ b/mm/vmscan.c > > @@ -831,6 +831,8 @@ static unsigned long shrink_page_list(struct list_head *page_list, > > * Try to allocate it some swap space here. > > */ > > if (PageAnon(page) && !PageSwapCache(page)) { > > + if (priority >= DEF_PRIORITY - 2) > > + goto keep_locked; > > if (!(sc->gfp_mask & __GFP_IO)) > > goto keep_locked; > > if (!add_to_swap(page)) > > Hm, how about not scanning LRU_ANON rather than checking here ? > Add some bias to get_scan_count() or some.. > If you think to need rotation of LRU, only kswapd should do that..
Absolutely, it would require more tuning. This patch was really a 'hey, how about we do something like this? anyone tried that before?'
I keep those things in mind if I pursue this further, thanks.
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