From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 1878 invoked by alias); 15 Dec 2009 09:11:45 -0000 Received: (qmail 1870 invoked by uid 22791); 15 Dec 2009 09:11:44 -0000 X-SWARE-Spam-Status: No, hits=-2.5 required=5.0 tests=AWL,BAYES_00 X-Spam-Check-By: sourceware.org Received: from smarthost03.mail.zen.net.uk (HELO smarthost03.mail.zen.net.uk) (212.23.3.142) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Tue, 15 Dec 2009 09:11:38 +0000 Received: from [82.69.137.158] (helo=[10.17.20.102]) by smarthost03.mail.zen.net.uk with esmtp (Exim 4.63) (envelope-from ) id 1NKTRP-0000Aq-Rq; Tue, 15 Dec 2009 09:11:35 +0000 Message-ID: <4B2752C6.4050804@undo-software.com> Date: Tue, 15 Dec 2009 09:11:00 -0000 From: Greg Law User-Agent: Thunderbird 2.0.0.21 (X11/20090320) MIME-Version: 1.0 To: Sean Chen CC: Hui Zhu , gdb@sourceware.org Subject: Re: UndoDB's performance References: <5e81cb500912040734u5ce67afdpd6a2d0e63173f908@mail.gmail.com> <5e81cb500912140518r2ad3f2fdrd0dd5a546e6d8a33@mail.gmail.com> <5e81cb500912141840s389859c2r9c56dd8800adb731@mail.gmail.com> <5e81cb500912142326t1bd545ek9180661d8bac10fe@mail.gmail.com> In-Reply-To: <5e81cb500912142326t1bd545ek9180661d8bac10fe@mail.gmail.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 8bit X-Originating-Smarthost03-IP: [82.69.137.158] Mailing-List: contact gdb-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-owner@sourceware.org X-SW-Source: 2009-12/txt/msg00093.txt.bz2 Sean Chen wrote: > On Tue, Dec 15, 2009 at 11:56 AM, Hui Zhu wrote: >> I did some test but its speed close to prec. Some others was better. >> Maybe it have some special performance technology for some code. >> >> Hui >> >> On Tue, Dec 15, 2009 at 10:40, Sean Chen wrote: >>> On Mon, Dec 14, 2009 at 11:07 PM, Hui Zhu wrote: >>>> Try undodb. >>>> >>>> On Mon, Dec 14, 2009 at 21:18, Sean Chen wrote: >>>>> On Mon, Dec 14, 2009 at 7:14 PM, Hui Zhu wrote: >>>>>> gdb-7 reverse debugging accelerator. >>>>>> Regular gdb-7 reverse runs apps 40,000x slower >>>>>> UndoDB+gdb-7 reverse runs apps 1.7x slower! >>>>>> >>>>>> >>>>>> Are you really do some try? >>>>>> I suggest you do some test on it. :) >>>>>> >>>>>> Thanks, >>>>>> Hui >>>>>> >>>>>> On Fri, Dec 4, 2009 at 23:34, Sean Chen wrote: >>>>>>> On UndoDb’s website, I saw the following ad. >>>>>>> >>>>>>> Regular gdb-7 reverse runs apps 40,000x slower >>>>>>> UndoDB+gdb-7 reverse runs apps 1.7x slower! >>>>>>> >>>>>>> In my experiment, gdb-7 reverse does run apps more than 20,000x >>>>>>> slower. How does UndoDB improve the performance so much without a >>>>>>> simulator and without record? Below is its self-introduction on the >>>>>>> website. UndoDB's "snapshot-and-replay" technique stores periodic >>>>>>> copy-on-write snapshots of the application and only non-deterministic >>>>>>> inputs (system calls, thread-switches, shared memory reads, etc). >>>>>>> >>>>>>> Are there any obvious disadvantages in UndoDB? I tried to search >>>>>>> UndoDB in the archive of the mailing list, however, little discussion >>>>>>> is found. >>>>>>> >>>>>>> -- >>>>>>> Best Regards, >>>>>>> Sean Chen >>>>>>> >>>>> That’s UndoDB’s ad on its website. >>>>> >>>>> In my experiment, gdb-7 reverse runs apps about 22,000x slower. >>>>> >>>>> -- >>>>> Best Regards, >>>>> Sean Chen >>>>> >>> I also tried UndoDB, and it is really fast. So I am sure they are >>> using different strategy. >>> >>> -- >>> Best Regards, >>> Sean Chen >>> > > It might not use process record technique like your design. > > Below is its self-introduction on its website. > UndoDB's "snapshot-and-replay" technique stores periodic copy-on-write > snapshots of the application and only non-deterministic inputs (system > calls, thread-switches, shared memory reads, etc). > > Any comments? Yes, I can confirm that's what we do. We did it that way (and generally tried very hard) to get the best record-time performance. To answer the OP, the downside is replay mode performance, namely stepping backwards, will be worse because you have a lot more work to do. You also need to store the snapshots, although as noted, copy-on-write can mitigate this cost. Greg -- Greg Law, Undo Software http://undo-software.com/