From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
To: balbir@linux.vnet.ibm.com
Cc: linux-mm@kvack.org, Sudhir Kumar <skumar@linux.vnet.ibm.com>,
YAMAMOTO Takashi <yamamoto@valinux.co.jp>,
Bharata B Rao <bharata@in.ibm.com>,
Paul Menage <menage@google.com>,
lizf@cn.fujitsu.com, linux-kernel@vger.kernel.org,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
David Rientjes <rientjes@google.com>,
Pavel Emelianov <xemul@openvz.org>,
Dhaval Giani <dhaval@linux.vnet.ibm.com>,
Rik van Riel <riel@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 0/4] Memory controller soft limit patches (v3)
Date: Mon, 2 Mar 2009 16:06:02 +0900 [thread overview]
Message-ID: <20090302160602.521928a5.kamezawa.hiroyu@jp.fujitsu.com> (raw)
In-Reply-To: <20090302063649.GJ11421@balbir.in.ibm.com>
On Mon, 2 Mar 2009 12:06:49 +0530
Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
> * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-03-02 15:21:28]:
>
> > On Mon, 2 Mar 2009 11:35:19 +0530
> > Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
> >
> > > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-03-02 14:32:50]:
> > >
> > > > On Mon, 2 Mar 2009 10:10:43 +0530
> > > > Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
> > > >
> > > > > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-03-02 09:24:04]:
> > > > >
> > > > > > On Sun, 01 Mar 2009 11:59:59 +0530
> > > > > > Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
> > > > > >
> > > > > > >
> > > > > > > From: Balbir Singh <balbir@linux.vnet.ibm.com>
> > > >
> > > > > >
> > > > > > At first, it's said "When cgroup people adds something, the kernel gets slow".
> > > > > > This is my start point of reviewing. Below is comments to this version of patch.
> > > > > >
> > > > > > 1. I think it's bad to add more hooks to res_counter. It's enough slow to give up
> > > > > > adding more fancy things..
> > > > >
> > > > > res_counters was desgined to be extensible, why is adding anything to
> > > > > it going to make it slow, unless we turn on soft_limits?
> > > > >
> > > > You inserted new "if" logic in the core loop.
> > > > (What I want to say here is not that this is definitely bad but that "isn't there
> > > > any alternatives which is less overhead.)
> > > >
> > > >
> > > > > >
> > > > > > 2. please avoid to add hooks to hot-path. In your patch, especially a hook to
> > > > > > mem_cgroup_uncharge_common() is annoying me.
> > > > >
> > > > > If soft limits are not enabled, the function does a small check and
> > > > > leaves.
> > > > >
> > > > &soft_fail_res is passed always even if memory.soft_limit==ULONG_MAX
> > > > res_counter_soft_limit_excess() adds one more function call and spinlock, and irq-off.
> > > >
> > >
> > > OK, I see that overhead.. I'll figure out a way to work around it.
> > >
> > > > > >
> > > > > > 3. please avoid to use global spinlock more.
> > > > > > no lock is best. mutex is better, maybe.
> > > > > >
> > > > >
> > > > > No lock to update a tree which is update concurrently?
> > > > >
> > > > Using tree/sort itself is nonsense, I believe.
> > > >
> > >
> > > I tried using prio trees in the past, but they are not easy to update
> > > either. I won't mind asking for suggestions for a data structure that
> > > can scaled well, allow quick insert/delete and search.
> > >
> > Now, because the routine is called by kswapd() not by try_to_free.....
> >
> > It's not necessary to be very very fast. That's my point.
> >
>
> OK, I get your point, but whay does that make RB-Tree data structure non-sense?
>
1. Until memory-shortage, rb-tree is kept to be updated and the users(kernel)
has to pay its maintainace/check cost, whici is unnecessary.
Considering trade-off, paying cost only when memory-shortage happens tend to
be reasonable way.
2. Current "exceed" just shows "How much we got over my soft limit" but doesn't
tell any information per-node/zone. Considering this, this rb-tree
information will not be able to help kswapd (on NUMA).
But maintain per-node information uses too much resource.
Considering above 2, it's not bad to find victim by proper logic
from balance_pgdat() by using mem_cgroup_select_victim().
like this:
==
struct mem_cgroup *select_vicitim_at_soft_limit_via_balance_pgdat(int nid, int zid)
{
while (?) {
vitcim = mem_cgroup_select_victim(init_mem_cgroup); #need some modification.
if (victim is not over soft-limit)
continue;
/* Ok this is candidate */
usage = mem_cgroup_nid_zid_usage(mem, nid, zid); #get sum of active/inactive
if (usage_is_enough_big)
return victim;
}
}
balance_pgdat()
...... find target zone....
...
mem = select_victime_at_soft_limit_via_balance_pgdat(nid, zid)
if (mem)
sc->mem = mem;
shrink_zone();
if (mem) {
sc->mem = NULL;
css_put(&mem->css);
}
==
We have to pay scan cost but it will not be too big(if there are not thousands of memcg.)
Under above, round-robin rotation is used rather than sort.
Maybe I can show you sample.....(but I'm a bit busy.)
Thanks,
-Kame
next prev parent reply other threads:[~2009-03-02 7:07 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-01 6:29 [PATCH 0/4] Memory controller soft limit patches (v3) Balbir Singh
2009-03-01 6:30 ` [PATCH 1/4] Memory controller soft limit documentation (v3) Balbir Singh
2009-03-01 6:30 ` [PATCH 2/4] Memory controller soft limit interface (v3) Balbir Singh
2009-03-02 2:03 ` KAMEZAWA Hiroyuki
2009-03-02 4:46 ` Balbir Singh
2009-03-02 5:35 ` KAMEZAWA Hiroyuki
2009-03-02 6:07 ` Balbir Singh
2009-03-02 6:19 ` KAMEZAWA Hiroyuki
2009-03-02 6:29 ` Balbir Singh
2009-03-01 6:30 ` [PATCH 3/4] Memory controller soft limit organize cgroups (v3) Balbir Singh
2009-03-01 6:30 ` [PATCH 4/4] Memory controller soft limit reclaim on contention (v3) Balbir Singh
2009-03-02 3:08 ` KOSAKI Motohiro
2009-03-02 4:44 ` Balbir Singh
2009-03-03 2:43 ` KOSAKI Motohiro
2009-03-03 11:17 ` Balbir Singh
2009-03-04 0:07 ` KOSAKI Motohiro
2009-03-02 0:24 ` [PATCH 0/4] Memory controller soft limit patches (v3) KAMEZAWA Hiroyuki
2009-03-02 4:40 ` Balbir Singh
2009-03-02 5:32 ` KAMEZAWA Hiroyuki
2009-03-02 6:05 ` Balbir Singh
2009-03-02 6:18 ` KAMEZAWA Hiroyuki
2009-03-02 17:52 ` Balbir Singh
2009-03-03 0:03 ` KAMEZAWA Hiroyuki
2009-03-03 11:23 ` Balbir Singh
2009-03-02 6:21 ` KAMEZAWA Hiroyuki
2009-03-02 6:36 ` Balbir Singh
2009-03-02 7:06 ` KAMEZAWA Hiroyuki [this message]
2009-03-02 7:17 ` KAMEZAWA Hiroyuki
2009-03-02 12:42 ` Balbir Singh
2009-03-02 14:04 ` KAMEZAWA Hiroyuki
2009-03-02 17:41 ` Balbir Singh
2009-03-02 23:59 ` KAMEZAWA Hiroyuki
2009-03-03 11:12 ` Balbir Singh
2009-03-03 11:50 ` KAMEZAWA Hiroyuki
2009-03-03 13:14 ` Balbir Singh
2009-03-05 9:04 ` KAMEZAWA Hiroyuki
2009-03-05 9:13 ` KAMEZAWA Hiroyuki
2009-03-05 15:26 ` Balbir Singh
2009-03-05 23:53 ` KAMEZAWA Hiroyuki
2009-03-06 3:23 ` KAMEZAWA Hiroyuki
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20090302160602.521928a5.kamezawa.hiroyu@jp.fujitsu.com \
--to=kamezawa.hiroyu@jp.fujitsu.com \
--cc=akpm@linux-foundation.org \
--cc=balbir@linux.vnet.ibm.com \
--cc=bharata@in.ibm.com \
--cc=dhaval@linux.vnet.ibm.com \
--cc=kosaki.motohiro@jp.fujitsu.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=lizf@cn.fujitsu.com \
--cc=menage@google.com \
--cc=riel@redhat.com \
--cc=rientjes@google.com \
--cc=skumar@linux.vnet.ibm.com \
--cc=xemul@openvz.org \
--cc=yamamoto@valinux.co.jp \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).