From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sedat Dilek Subject: Re: 2.6.39-rc4+: Kernel leaking memory during FS scanning, regression? Date: Tue, 26 Apr 2011 21:17:28 +0200 Message-ID: References: <20110425203606.4e78246c@neptune.home> <20110425191607.GL2468@linux.vnet.ibm.com> <20110425231016.34b4293e@neptune.home> <20110425214933.GO2468@linux.vnet.ibm.com> <20110426081904.0d2b1494@pluto.restena.lu> <20110426112756.GF4308@linux.vnet.ibm.com> <20110426183859.6ff6279b@neptune.home> <20110426185036.GG2135@linux.vnet.ibm.com> Reply-To: sedat.dilek@gmail.com Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Cc: Linus Torvalds , =?UTF-8?Q?Bruno_Pr=C3=A9mont?= , Ingo Molnar , Peter Zijlstra , Mike Frysinger , KOSAKI Motohiro , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, "Paul E. McKenney" , Pekka Enberg To: paulmck@linux.vnet.ibm.com Return-path: In-Reply-To: <20110426185036.GG2135@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org On Tue, Apr 26, 2011 at 8:50 PM, Paul E. McKenney wrote: > On Tue, Apr 26, 2011 at 10:12:39AM -0700, Linus Torvalds wrote: >> On Tue, Apr 26, 2011 at 9:38 AM, Bruno Pr=C3=A9mont >> wrote: >> > >> > Here it comes: >> > >> > rcu_kthread (when build processes are STOPped): >> > [ =C2=A0836.050003] rcu_kthread =C2=A0 =C2=A0 R running =C2=A0 7324 = =C2=A0 =C2=A0 6 =C2=A0 =C2=A0 =C2=A02 0x00000000 >> > [ =C2=A0836.050003] =C2=A0dd473f28 00000046 5a000240 dd65207c dd407360= dd651d40 0000035c dd473ed8 >> > [ =C2=A0836.050003] =C2=A0c10bf8a2 c14d63d8 dd65207c dd473f28 dd445040= dd445040 dd473eec c10be848 >> > [ =C2=A0836.050003] =C2=A0dd651d40 dd407360 ddfdca00 dd473f14 c10bfde2= 00000000 00000001 000007b6 >> > [ =C2=A0836.050003] Call Trace: >> > [ =C2=A0836.050003] =C2=A0[] ? check_object+0x92/0x210 >> > [ =C2=A0836.050003] =C2=A0[] ? init_object+0x38/0x70 >> > [ =C2=A0836.050003] =C2=A0[] ? free_debug_processing+0x112/0= x1f0 >> > [ =C2=A0836.050003] =C2=A0[] ? lock_timer_base+0x2d/0x70 >> > [ =C2=A0836.050003] =C2=A0[] schedule_timeout+0x137/0x280 >> >> Hmm. >> >> I'm adding Ingo and Peter to the cc, because this whole "rcu_kthread >> is running, but never actually running" is starting to smell like a >> scheduler issue. >> >> Peter/Ingo: RCUTINY seems to be broken for Bruno. During any kind of >> heavy workload, at some point it looks like rcu_kthread simply stops >> making any progress. It's constantly in runnable state, but it doesn't >> actually use any CPU time, and it's not processing the RCU callbacks, >> so the RCU memory freeing isn't happening, and slabs just build up >> until the machine dies. >> >> And it really is RCUTINY, because the thing doesn't happen with the >> regular tree-RCU. > > The difference between TINY_RCU and TREE_RCU is that TREE_RCU still uses > softirq for the core RCU processing. =C2=A0TINY_RCU switched to a kthread > when I implemented RCU priority boosting. =C2=A0There is a similar change= in > my -rcu tree that makes TREE_RCU use kthreads, and Sedat has been running > into a very similar problem with that change in place. =C2=A0Which is why= I > do not yet push it to the -next tree. > >> This is without CONFIG_RCU_BOOST_PRIO, so we basically have >> >> =C2=A0 =C2=A0 =C2=A0 =C2=A0 struct sched_param sp; >> >> =C2=A0 =C2=A0 =C2=A0 =C2=A0 rcu_kthread_task =3D kthread_run(rcu_kthread= , NULL, "rcu_kthread"); >> =C2=A0 =C2=A0 =C2=A0 =C2=A0 sp.sched_priority =3D RCU_BOOST_PRIO; >> =C2=A0 =C2=A0 =C2=A0 =C2=A0 sched_setscheduler_nocheck(rcu_kthread_task,= SCHED_FIFO, &sp); >> >> where RCU_BOOST_PRIO is 1 for the non-boost case. > > Good point! =C2=A0Bruno, Sedat, could you please set CONFIG_RCU_BOOST_PRI= O to > (say) 50, and see if this still happens? =C2=A0(I bet that you do, but...= ) > What's with CONFIG_RCU_BOOST_DELAY setting? Are those values OK? $ egrep 'M486|M686|X86_UP|CONFIG_SMP|NR_CPUS|PREEMPT|_RCU|_HIGHMEM|PAE' .co= nfig CONFIG_TREE_PREEMPT_RCU=3Dy CONFIG_PREEMPT_RCU=3Dy CONFIG_RCU_TRACE=3Dy CONFIG_RCU_FANOUT=3D32 # CONFIG_RCU_FANOUT_EXACT is not set CONFIG_TREE_RCU_TRACE=3Dy CONFIG_RCU_BOOST=3Dy CONFIG_RCU_BOOST_PRIO=3D50 CONFIG_RCU_BOOST_DELAY=3D500 CONFIG_SMP=3Dy # CONFIG_M486 is not set CONFIG_M686=3Dy CONFIG_NR_CPUS=3D32 # CONFIG_PREEMPT_NONE is not set # CONFIG_PREEMPT_VOLUNTARY is not set CONFIG_PREEMPT=3Dy CONFIG_HIGHMEM4G=3Dy # CONFIG_HIGHMEM64G is not set CONFIG_HIGHMEM=3Dy CONFIG_DEBUG_OBJECTS_RCU_HEAD=3Dy CONFIG_DEBUG_PREEMPT=3Dy # CONFIG_SPARSE_RCU_POINTER is not set # CONFIG_DEBUG_HIGHMEM is not set CONFIG_RCU_TORTURE_TEST=3Dm CONFIG_RCU_CPU_STALL_TIMEOUT=3D60 CONFIG_RCU_CPU_STALL_VERBOSE=3Dy CONFIG_PREEMPT_TRACER=3Dy - Sedat - >> Is that so low that even the idle thread will take priority? It's a UP >> config with PREEMPT_VOLUNTARY. So pretty much _all_ the stars are >> aligned for odd scheduling behavior. >> >> Other users of SCHED_FIFO tend to set the priority really high (eg >> "MAX_RT_PRIO-1" is clearly the default one - softirq's, watchdog), but >> "1" is not unheard of either (touchscreen/ucb1400_ts and >> mmc/core/sdio_irq), and there are some other random choises out tere. >> >> Any ideas? > > I have found one bug so far in my code, but it only affects TREE_RCU > in my -rcu tree, and even then only if HOTPLUG_CPU is enabled. =C2=A0I am > testing a fix, but I expect Sedat's tests to still break. > > I gave Sedat a patch that make rcu_kthread() run at normal (non-realtime) > priority, and he did not see the failure. =C2=A0So running non-realtime a= t > least greatly reduces the probability of failure. > > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0Thanx, Paul > -- > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" = in > the body of a message to majordomo@vger.kernel.org > More majordomo info at =C2=A0http://vger.kernel.org/majordomo-info.html > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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