linux-kernel - Re: [patch] mm: vmscan implement per-zone shrinkers

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20101116074717.GB3460@amd>
Date:	Tue, 16 Nov 2010 18:47:17 +1100
From:	Nick Piggin <npiggin@...nel.dk>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	Nick Piggin <npiggin@...nel.dk>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [patch] mm: vmscan implement per-zone shrinkers

On Mon, Nov 15, 2010 at 09:50:36AM +0900, KOSAKI Motohiro wrote:
> > > @@ -1835,8 +1978,6 @@ static void shrink_zone(int priority, st
> > >  			break;
> > >  	}
> > >  
> > > -	sc->nr_reclaimed = nr_reclaimed;
> > > -
> > >  	/*
> > >  	 * Even if we did not try to evict anon pages at all, we want to
> > >  	 * rebalance the anon lru active/inactive ratio.
> > > @@ -1844,6 +1985,23 @@ static void shrink_zone(int priority, st
> > >  	if (inactive_anon_is_low(zone, sc))
> > >  		shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
> > >  
> > > +	/*
> > > +	 * Don't shrink slabs when reclaiming memory from
> > > +	 * over limit cgroups
> > > +	 */
> > > +	if (sc->may_reclaim_slab) {
> > > +		struct reclaim_state *reclaim_state = current->reclaim_state;
> > > +
> > > +		shrink_slab(zone, sc->nr_scanned - nr_scanned,
> > 
> > Doubtful calculation. What mean "sc->nr_scanned - nr_scanned"?
> > I think nr_scanned simply keep old slab balancing behavior.
> 
> And per-zone reclaim can lead to new issue. On 32bit highmem system,
> theorically the system has following memory usage.
> 
> ZONE_HIGHMEM: 100% used for page cache
> ZONE_NORMAL:  100% used for slab
> 
> So, traditional page-cache/slab balancing may not work. I think following

Yes, in theory you are right. I guess in theory the same hole exists
if we have 0% page cache reclaimable globally, but this may be slightly
more likely to hit.


> new calculation or somethinhg else is necessary.
> 
> 	if (zone_reclaimable_pages() > NR_SLAB_RECLAIMABLE) {
> 		using current calculation
> 	} else {
> 		shrink number of "objects >> reclaim-priority" objects
> 		(as page cache scanning calculation)
> 	}
> 
> However, it can be separate this patch, perhaps.

I agree. In fact, perhaps the new calculation would work well in all
cases anyway, so maybe we should move away from making slab reclaim a
slave to pagecache reclaim.

Can we approach that in subsequent patches?

Thanks,
Nick

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/