From: KOSAKI Motohiro <kosaki.motohiro-+CUm20s59erQFUHtdCDX3A@public.gmane.org> To: Roland Dreier <rdreier-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org> Cc: kosaki.motohiro-+CUm20s59erQFUHtdCDX3A@public.gmane.org, torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, jsquyres-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org, linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, general-ZwoEplunGu1OwGhvXhtEPSCwEArCW2h5@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Subject: Re: [GIT PULL] please pull ummunotify Date: Fri, 11 Sep 2009 15:11:36 +0900 (JST) [thread overview] Message-ID: <20090911150552.DB68.A69D9226@jp.fujitsu.com> (raw) In-Reply-To: <adatyzahvbm.fsf-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org> Hi Thank you explanation. > > > Can I this version already solved fork() + COW issue? if so, could you > > please explain what happen at fork. Obviously RDMA point to either parent > > or child page, not both. but Corrent COW rule is, first touch process > > get copyed page and other process still own original page. I think it's > > unpecected behavior form RDMA. > > No, ummunotify doesn't really help that much with fork() + COW. If a > parent forks and then touches pages that are actively in use for RDMA, > then of course they get COWed and RDMA goes to the wrong memory (from > the point of view of the parent). So, Can we assume OpenMPI user process doesn't such thing? Parhaps, madvise(DONTFORK) or vfork() avoid this issue. but I'm not sure all program in the world do that. > ummunotify does deal with the case where a process forks and touches > memory that was used for RDMA but no longer is -- in that case, the MPI > library has a chance to flush its registration cache because it will get > a ummunotify event invalidating the old mapping. > > The real purpose of ummunotify is to allow MPI implementations to cache > registrations, even when the MPI library is used with an application > that does funny things for allocation (mmap()/munmap() or brk(), etc). Yup, that's very worth. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> To: Roland Dreier <rdreier@cisco.com> Cc: kosaki.motohiro@jp.fujitsu.com, torvalds@linux-foundation.org, akpm@linux-foundation.org, jsquyres@cisco.com, linux-rdma@vger.kernel.org, general@lists.openfabrics.org, linux-kernel@vger.kernel.org Subject: Re: [GIT PULL] please pull ummunotify Date: Fri, 11 Sep 2009 15:11:36 +0900 (JST) [thread overview] Message-ID: <20090911150552.DB68.A69D9226@jp.fujitsu.com> (raw) In-Reply-To: <adatyzahvbm.fsf@cisco.com> Hi Thank you explanation. > > > Can I this version already solved fork() + COW issue? if so, could you > > please explain what happen at fork. Obviously RDMA point to either parent > > or child page, not both. but Corrent COW rule is, first touch process > > get copyed page and other process still own original page. I think it's > > unpecected behavior form RDMA. > > No, ummunotify doesn't really help that much with fork() + COW. If a > parent forks and then touches pages that are actively in use for RDMA, > then of course they get COWed and RDMA goes to the wrong memory (from > the point of view of the parent). So, Can we assume OpenMPI user process doesn't such thing? Parhaps, madvise(DONTFORK) or vfork() avoid this issue. but I'm not sure all program in the world do that. > ummunotify does deal with the case where a process forks and touches > memory that was used for RDMA but no longer is -- in that case, the MPI > library has a chance to flush its registration cache because it will get > a ummunotify event invalidating the old mapping. > > The real purpose of ummunotify is to allow MPI implementations to cache > registrations, even when the MPI library is used with an application > that does funny things for allocation (mmap()/munmap() or brk(), etc). Yup, that's very worth.
next prev parent reply other threads:[~2009-09-11 6:11 UTC|newest] Thread overview: 82+ messages / expand[flat|nested] mbox.gz Atom feed top 2009-09-11 4:38 [GIT PULL] please pull ummunotify Roland Dreier 2009-09-11 4:38 ` Roland Dreier 2009-09-15 11:34 ` Pavel Machek [not found] ` <20090915113434.GF1328-+ZI9xUNit7I@public.gmane.org> 2009-09-15 14:57 ` [ofa-general] " Roland Dreier 2009-09-15 14:57 ` Roland Dreier [not found] ` <ada7hw0gsqz.fsf-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org> 2009-09-28 20:49 ` Pavel Machek 2009-09-28 20:49 ` Pavel Machek [not found] ` <20090928204923.GA1960-I/5MKhXcvmPrBKCeMvbIDA@public.gmane.org> 2009-09-28 21:40 ` Jason Gunthorpe 2009-09-28 21:40 ` Jason Gunthorpe [not found] ` <aday6omhz9d.fsf-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org> 2009-09-11 5:56 ` KOSAKI Motohiro 2009-09-11 5:56 ` KOSAKI Motohiro 2009-09-11 6:03 ` [ofa-general] " Roland Dreier 2009-09-11 6:03 ` Roland Dreier [not found] ` <adatyzahvbm.fsf-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org> 2009-09-11 6:11 ` KOSAKI Motohiro [this message] 2009-09-11 6:11 ` KOSAKI Motohiro [not found] ` <20090911150552.DB68.A69D9226-+CUm20s59erQFUHtdCDX3A@public.gmane.org> 2009-09-11 16:42 ` Gleb Natapov 2009-09-11 16:42 ` Gleb Natapov 2009-09-11 6:15 ` Brice Goglin [not found] ` <4AA9EAF7.5010401-MZpvjPyXg2s@public.gmane.org> 2009-09-11 6:21 ` KOSAKI Motohiro 2009-09-11 6:21 ` KOSAKI Motohiro 2009-09-11 6:22 ` Roland Dreier 2009-09-11 6:22 ` Roland Dreier 2009-09-11 6:40 ` [ofa-general] " Jason Gunthorpe 2009-09-11 6:40 ` Jason Gunthorpe [not found] ` <20090911064019.GZ4973-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org> 2009-09-11 16:58 ` Roland Dreier 2009-09-11 16:58 ` Roland Dreier [not found] ` <adaljklifkt.fsf-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org> 2009-09-15 7:03 ` KOSAKI Motohiro 2009-09-15 7:03 ` KOSAKI Motohiro 2009-09-15 8:27 ` Roland Dreier 2009-09-15 8:27 ` Roland Dreier 2009-09-15 12:38 ` Jeff Squyres 2009-09-15 12:38 ` Jeff Squyres 2009-09-16 16:30 ` Roland Dreier 2009-09-16 16:30 ` Roland Dreier 2009-09-16 16:40 ` [ofa-general] " Linus Torvalds 2009-09-16 16:40 ` Linus Torvalds 2009-09-17 11:30 ` Peter Zijlstra 2009-09-17 11:30 ` Peter Zijlstra 2009-09-17 14:24 ` [ofa-general] " Roland Dreier [not found] ` <adafxalejiq.fsf-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org> 2009-09-17 14:32 ` Roland Dreier 2009-09-17 14:32 ` Roland Dreier [not found] ` <adaab0tej5c.fsf-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org> 2009-09-17 14:49 ` Peter Zijlstra 2009-09-17 14:49 ` Peter Zijlstra 2009-09-17 15:03 ` Roland Dreier 2009-09-17 15:03 ` Roland Dreier [not found] ` <adazl8td35u.fsf-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org> 2009-09-17 15:22 ` Peter Zijlstra 2009-09-17 15:22 ` Peter Zijlstra 2009-09-17 15:45 ` Roland Dreier 2009-09-17 15:45 ` Roland Dreier [not found] ` <adatyz1d17q.fsf-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org> 2009-09-18 11:50 ` Ingo Molnar 2009-09-18 11:50 ` Ingo Molnar 2009-09-29 17:13 ` Pavel Machek 2009-09-29 17:13 ` Pavel Machek [not found] ` <20090929171332.GD14405-I/5MKhXcvmPrBKCeMvbIDA@public.gmane.org> 2009-09-30 9:44 ` Ingo Molnar 2009-09-30 9:44 ` Ingo Molnar [not found] ` <20090930094456.GD24621-X9Un+BFzKDI@public.gmane.org> 2009-09-30 16:02 ` Jason Gunthorpe 2009-09-30 16:02 ` Jason Gunthorpe [not found] ` <20090930160232.GZ22310-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org> 2009-10-12 18:19 ` Ingo Molnar 2009-10-12 18:19 ` Ingo Molnar [not found] ` <20091012181944.GF17138-X9Un+BFzKDI@public.gmane.org> 2009-10-12 19:30 ` Jason Gunthorpe 2009-10-12 19:30 ` Jason Gunthorpe 2009-10-12 20:20 ` Ingo Molnar [not found] ` <20091012202046.GA7648-X9Un+BFzKDI@public.gmane.org> 2009-10-13 4:05 ` Jason Gunthorpe 2009-10-13 4:05 ` Jason Gunthorpe 2009-10-13 6:40 ` Ingo Molnar [not found] ` <20091013064006.GC9470-X9Un+BFzKDI@public.gmane.org> 2009-10-13 16:27 ` Jason Gunthorpe 2009-10-13 16:27 ` Jason Gunthorpe 2009-10-13 5:43 ` Brice Goglin [not found] ` <4AD41373.8010108-MZpvjPyXg2s@public.gmane.org> 2009-10-13 6:38 ` Ingo Molnar 2009-10-13 6:38 ` Ingo Molnar 2009-09-30 17:06 ` Roland Dreier 2009-09-30 17:06 ` Roland Dreier 2009-10-02 16:32 ` Roland Dreier 2009-10-02 16:32 ` Roland Dreier [not found] ` <ada3a61rc3j.fsf-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org> 2009-10-02 20:45 ` Pavel Machek 2009-10-02 20:45 ` Pavel Machek 2009-10-07 22:34 ` Roland Dreier 2009-10-07 22:34 ` Roland Dreier [not found] ` <ada3a5uq1dk.fsf-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org> 2009-10-12 17:33 ` Peter Zijlstra 2009-10-12 17:33 ` Peter Zijlstra 2009-09-17 14:43 ` Peter Zijlstra 2009-09-17 14:43 ` Peter Zijlstra
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