From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
To: David Rientjes <rientjes@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Greg Thelen <gthelen@google.com>,
Aruna Ramakrishna <aruna.ramakrishna@oracle.com>,
Christoph Lameter <cl@linux.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [patch] mm, slab: faster active and free stats
Date: Mon, 28 Nov 2016 16:40:02 +0900 [thread overview]
Message-ID: <20161128074001.GA32105@js1304-P5Q-DELUXE> (raw)
In-Reply-To: <alpine.DEB.2.10.1611110222440.16406@chino.kir.corp.google.com>
On Fri, Nov 11, 2016 at 02:30:39AM -0800, David Rientjes wrote:
> On Fri, 11 Nov 2016, Joonsoo Kim wrote:
>
> > Hello, David.
> >
> > Maintaining acitve/free_slab counters looks so complex. And, I think
> > that we don't need to maintain these counters for faster slabinfo.
> > Key point is to remove iterating n->slabs_partial list.
> >
> > We can calculate active slab/object by following equation as you did in
> > this patch.
> >
> > active_slab(n) = n->num_slab - the number of free_slab
> > active_object(n) = n->num_slab * cachep->num - n->free_objects
> >
> > To get the number of free_slab, we need to iterate n->slabs_free list
> > but I guess it would be small enough.
> >
> > If you don't like to iterate n->slabs_free list in slabinfo, just
> > maintaining the number of slabs_free would be enough.
> >
>
> Hi Joonsoo,
>
> It's a good point, although I don't think the patch has overly complex
> logic to keep track of slab state.
>
> We don't prefer to do any iteration in get_slabinfo() since users can
> read /proc/slabinfo constantly; it's better to just settle the stats when
> slab state changes instead of repeating an expensive operation over and
> over if someone is running slabtop(1) or /proc/slabinfo is scraped
> regularly for stats.
>
> That said, I imagine there are more clever ways to arrive at the same
> answer, and you bring up a good point about maintaining a n->num_slabs and
> n->free_slabs rather than n->active_slabs and n->free_slabs.
>
> I don't feel strongly about either approach, but I think some improvement,
> such as what this patch provides, is needed to prevent how expensive
> simply reading /proc/slabinfo can be.
Hello,
Sorry for long delay.
I agree that this improvement is needed. Could you try the approach
that maintains n->num_slabs and n->free_slabs? I guess that it would be
simpler than this patch so more maintainable.
Thanks.
next prev parent reply other threads:[~2016-11-28 7:37 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-08 23:06 [patch] mm, slab: faster active and free stats David Rientjes
2016-11-08 23:17 ` Andrew Morton
2016-11-10 0:38 ` David Rientjes
2016-11-11 5:53 ` Joonsoo Kim
2016-11-11 10:30 ` David Rientjes
2016-11-28 7:40 ` Joonsoo Kim [this message]
2016-11-30 0:56 ` David Rientjes
2016-12-02 7:58 ` 김준수/선임연구원/SW Platform(연)AOT팀(iamjoonsoo.kim@lge.com)
2016-12-05 4:23 ` [patch -mm] mm, slab: maintain total slab count instead of active count David Rientjes
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