From: Ingo Molnar <mingo-X9Un+BFzKDI@public.gmane.org> To: Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org> Cc: Pavel Machek <pavel-+ZI9xUNit7I@public.gmane.org>, Roland Dreier <rdreier-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>, Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>, linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Paul Mackerras <paulus-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>, Anton Blanchard <anton-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>, general-ZwoEplunGu1OwGhvXhtEPSCwEArCW2h5@public.gmane.org, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, Jeff Squyres <jsquyres-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org> Subject: Re: [ofa-general] Re: [GIT PULL] please pull ummunotify Date: Mon, 12 Oct 2009 20:19:44 +0200 [thread overview] Message-ID: <20091012181944.GF17138@elte.hu> (raw) In-Reply-To: <20090930160232.GZ22310-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org> * Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org> wrote: > On Wed, Sep 30, 2009 at 11:44:56AM +0200, Ingo Molnar wrote: > > > > OK. It would be nice to tie into something more general, but I > > > > think I agree -- perf counters are missing the filtering and the "no > > > > lost events" that ummunotify does have. [...] > > > > Performance events filtering is being worked on and now with the > > proper non-DoS limit you've added you can lose events too, dont you? > > So it's all a question of how much buffering to add - and with perf > > events too you can buffer arbitrary large amount of events. > > No, the ummunotify does not loose events, that is the fundamental > difference between it and all tracing schemes. > > Every call to ibv_reg_mr is paired with a call to ummunotify to create > a matching watcher. Both calls allocate some kernel memory, if one > fails the entire operation fails and userspace can do whatever it does > on memory allocation failure. We already support signal notification for perf events, and we also support two modi of perf ring-buffer overflow notification. Adding a third one that sends a signal when events are lost would be in line with that. This would allow you to have the OOM semantics of requesting a SIGBUS - or user-space could do other things: like print a warning in the app or ignore the event overflow. Which are all interesting things to do. (If you do that you might want to add that to 'perf top' or 'perf record' as well.) > After that point the scheme is perfectly lossless. Well if it can OOM it's not lossless, obviously. You just define "event loss" to be equivalent to "Destruction of the universe." ;-) Ingo -- 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: Ingo Molnar <mingo@elte.hu> To: Jason Gunthorpe <jgunthorpe@obsidianresearch.com> Cc: Pavel Machek <pavel@ucw.cz>, Roland Dreier <rdreier@cisco.com>, Peter Zijlstra <peterz@infradead.org>, linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org, Paul Mackerras <paulus@samba.org>, Anton Blanchard <anton@samba.org>, general@lists.openfabrics.org, akpm@linux-foundation.org, torvalds@linux-foundation.org, Jeff Squyres <jsquyres@cisco.com> Subject: Re: [ofa-general] Re: [GIT PULL] please pull ummunotify Date: Mon, 12 Oct 2009 20:19:44 +0200 [thread overview] Message-ID: <20091012181944.GF17138@elte.hu> (raw) In-Reply-To: <20090930160232.GZ22310@obsidianresearch.com> * Jason Gunthorpe <jgunthorpe@obsidianresearch.com> wrote: > On Wed, Sep 30, 2009 at 11:44:56AM +0200, Ingo Molnar wrote: > > > > OK. It would be nice to tie into something more general, but I > > > > think I agree -- perf counters are missing the filtering and the "no > > > > lost events" that ummunotify does have. [...] > > > > Performance events filtering is being worked on and now with the > > proper non-DoS limit you've added you can lose events too, dont you? > > So it's all a question of how much buffering to add - and with perf > > events too you can buffer arbitrary large amount of events. > > No, the ummunotify does not loose events, that is the fundamental > difference between it and all tracing schemes. > > Every call to ibv_reg_mr is paired with a call to ummunotify to create > a matching watcher. Both calls allocate some kernel memory, if one > fails the entire operation fails and userspace can do whatever it does > on memory allocation failure. We already support signal notification for perf events, and we also support two modi of perf ring-buffer overflow notification. Adding a third one that sends a signal when events are lost would be in line with that. This would allow you to have the OOM semantics of requesting a SIGBUS - or user-space could do other things: like print a warning in the app or ignore the event overflow. Which are all interesting things to do. (If you do that you might want to add that to 'perf top' or 'perf record' as well.) > After that point the scheme is perfectly lossless. Well if it can OOM it's not lossless, obviously. You just define "event loss" to be equivalent to "Destruction of the universe." ;-) Ingo
next prev parent reply other threads:[~2009-10-12 18:19 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 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 [this message] 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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