From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f72.google.com (mail-pg0-f72.google.com [74.125.83.72]) by kanga.kvack.org (Postfix) with ESMTP id 88B362806F4 for ; Tue, 22 Aug 2017 13:23:53 -0400 (EDT) Received: by mail-pg0-f72.google.com with SMTP id b8so92382502pgn.10 for ; Tue, 22 Aug 2017 10:23:53 -0700 (PDT) Received: from mga07.intel.com (mga07.intel.com. [134.134.136.100]) by mx.google.com with ESMTPS id g1si10022408pld.694.2017.08.22.10.23.51 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 22 Aug 2017 10:23:51 -0700 (PDT) From: "Liang, Kan" Subject: RE: [PATCH 1/2] sched/wait: Break up long wake list walk Date: Tue, 22 Aug 2017 17:23:47 +0000 Message-ID: <37D7C6CF3E00A74B8858931C1DB2F0775378A24A@SHSMSX103.ccr.corp.intel.com> References: <37D7C6CF3E00A74B8858931C1DB2F0775378761B@SHSMSX103.ccr.corp.intel.com> <20170818122339.24grcbzyhnzmr4qw@techsingularity.net> <37D7C6CF3E00A74B8858931C1DB2F077537879BB@SHSMSX103.ccr.corp.intel.com> <20170818144622.oabozle26hasg5yo@techsingularity.net> <37D7C6CF3E00A74B8858931C1DB2F07753787AE4@SHSMSX103.ccr.corp.intel.com> <20170818185455.qol3st2nynfa47yc@techsingularity.net> <20170821183234.kzennaaw2zt2rbwz@techsingularity.net> <37D7C6CF3E00A74B8858931C1DB2F07753788B58@SHSMSX103.ccr.corp.intel.com> In-Reply-To: <37D7C6CF3E00A74B8858931C1DB2F07753788B58@SHSMSX103.ccr.corp.intel.com> Content-Language: en-US Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: 'Mel Gorman' , 'Linus Torvalds' Cc: 'Mel Gorman' , "'Kirill A. Shutemov'" , 'Tim Chen' , 'Peter Zijlstra' , 'Ingo Molnar' , 'Andi Kleen' , 'Andrew Morton' , 'Johannes Weiner' , 'Jan Kara' , 'linux-mm' , 'Linux Kernel Mailing List' > > Covering both paths would be something like the patch below which > > spins until the page is unlocked or it should reschedule. It's not > > even boot tested as I spent what time I had on the test case that I > > hoped would be able to prove it really works. >=20 > I will give it a try. Although the patch doesn't trigger watchdog, the spin lock wait time is not small (0.45s). It may get worse again on larger systems. Irqsoff ftrace result. # tracer: irqsoff # # irqsoff latency trace v1.1.5 on 4.13.0-rc4+ # -------------------------------------------------------------------- # latency: 451753 us, #4/4, CPU#159 | (M:desktop VP:0, KP:0, SP:0 HP:0 #P:2= 24) # ----------------- # | task: fjsctest-233851 (uid:0 nice:0 policy:0 rt_prio:0) # ----------------- # =3D> started at: wake_up_page_bit # =3D> ended at: wake_up_page_bit # # # _------=3D> CPU# =20 # / _-----=3D> irqs-off =20 # | / _----=3D> need-resched =20 # || / _---=3D> hardirq/softirq=20 # ||| / _--=3D> preempt-depth =20 # |||| / delay =20 # cmd pid ||||| time | caller =20 # \ / ||||| \ | / =20 <...>-233851 159d... 0us@: _raw_spin_lock_irqsave <-wake_up_page_bit <...>-233851 159dN.. 451726us+: _raw_spin_unlock_irqrestore <-wake_up_pa= ge_bit <...>-233851 159dN.. 451754us!: trace_hardirqs_on <-wake_up_page_bit <...>-233851 159dN.. 451873us : =3D> unlock_page =3D> migrate_pages =3D> migrate_misplaced_page =3D> __handle_mm_fault =3D> handle_mm_fault =3D> __do_page_fault =3D> do_page_fault =3D> page_fault The call stack of wait_on_page_bit_common 100.00% (ffffffff971b252b) | ---__spinwait_on_page_locked | =20 |--96.81%--__migration_entry_wait | migration_entry_wait | do_swap_page | __handle_mm_fault | handle_mm_fault | __do_page_fault | do_page_fault | page_fault | | =20 | |--22.49%--0x123a2 | | | =20 | | --22.34%--start_thread | | =20 | |--15.69%--0x127bc | | | =20 | | --13.20%--start_thread | | =20 | |--13.48%--0x12352 | | | =20 | | --11.74%--start_thread | | =20 | |--13.43%--0x127f2 | | | =20 | | --11.25%--start_thread | | =20 | |--10.03%--0x1285e | | | =20 | | --8.59%--start_thread | | =20 | |--5.90%--0x12894 | | | =20 | | --5.03%--start_thread | | =20 | |--5.66%--0x12828 | | | =20 | | --4.81%--start_thread | | =20 | |--5.17%--0x1233c | | | =20 | | --4.46%--start_thread | | =20 | --4.72%--0x2b788 | | =20 | --4.72%--0x127a2 | start_thread | =20 --3.19%--do_huge_pmd_numa_page __handle_mm_fault handle_mm_fault __do_page_fault do_page_fault page_fault 0x2b788 0x127a2 start_thread >=20 > > > > diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index > > 79b36f57c3ba..31cda1288176 100644 > > --- a/include/linux/pagemap.h > > +++ b/include/linux/pagemap.h > > @@ -517,6 +517,13 @@ static inline void wait_on_page_locked(struct > > page > > *page) > > wait_on_page_bit(compound_head(page), PG_locked); } > > > > +void __spinwait_on_page_locked(struct page *page); static inline void > > +spinwait_on_page_locked(struct page *page) { > > + if (PageLocked(page)) > > + __spinwait_on_page_locked(page); > > +} > > + > > static inline int wait_on_page_locked_killable(struct page *page) { > > if (!PageLocked(page)) > > diff --git a/mm/filemap.c b/mm/filemap.c index > > a49702445ce0..c9d6f49614bc 100644 > > --- a/mm/filemap.c > > +++ b/mm/filemap.c > > @@ -1210,6 +1210,15 @@ int __lock_page_or_retry(struct page *page, > > struct mm_struct *mm, > > } > > } > > > > +void __spinwait_on_page_locked(struct page *page) { > > + do { > > + cpu_relax(); > > + } while (PageLocked(page) && !cond_resched()); > > + > > + wait_on_page_locked(page); > > +} > > + > > /** > > * page_cache_next_hole - find the next hole (not-present entry) > > * @mapping: mapping > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c index > > 90731e3b7e58..c7025c806420 100644 > > --- a/mm/huge_memory.c > > +++ b/mm/huge_memory.c > > @@ -1443,7 +1443,7 @@ int do_huge_pmd_numa_page(struct vm_fault > *vmf, > > pmd_t pmd) > > if (!get_page_unless_zero(page)) > > goto out_unlock; > > spin_unlock(vmf->ptl); > > - wait_on_page_locked(page); > > + spinwait_on_page_locked(page); > > put_page(page); > > goto out; > > } > > @@ -1480,7 +1480,7 @@ int do_huge_pmd_numa_page(struct vm_fault > *vmf, > > pmd_t pmd) > > if (!get_page_unless_zero(page)) > > goto out_unlock; > > spin_unlock(vmf->ptl); > > - wait_on_page_locked(page); > > + spinwait_on_page_locked(page); > > put_page(page); > > goto out; > > } > > diff --git a/mm/migrate.c b/mm/migrate.c index > > e84eeb4e4356..9b6c3fc5beac 100644 > > --- a/mm/migrate.c > > +++ b/mm/migrate.c > > @@ -308,7 +308,7 @@ void __migration_entry_wait(struct mm_struct > *mm, > > pte_t *ptep, > > if (!get_page_unless_zero(page)) > > goto out; > > pte_unmap_unlock(ptep, ptl); > > - wait_on_page_locked(page); > > + spinwait_on_page_locked(page); > > put_page(page); > > return; > > out: > > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org