From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [PATCH RFC 0/4]Porting Xentrace to kvm Date: Sun, 16 Mar 2008 17:12:41 +0100 Message-ID: <47DD46F9.5010809@web.de> References: <9D7649D18729DE4BB2BD7B494F7FEDC201084D2D@pdsmsx415.ccr.corp.intel.com> <47DD3CBB.9050201@qumranet.com> <47DD4085.7010607@web.de> <47DD4282.6010201@qumranet.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============1816343380==" Cc: kvm-devel , "Liu, Eric E" To: Avi Kivity Return-path: In-Reply-To: <47DD4282.6010201@qumranet.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces@lists.sourceforge.net Errors-To: kvm-devel-bounces@lists.sourceforge.net List-Id: kvm.vger.kernel.org This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --===============1816343380== Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig9E64D967E6FE085C06DE6D01" This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig9E64D967E6FE085C06DE6D01 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Avi Kivity wrote: > Jan Kiszka wrote: >> Avi Kivity wrote: >> =20 >>> Liu, Eric E wrote: >>> =20 >>>> Hi, >>>> The following patches port xentrace to kvm which is useful for >>>> performance tuning and debugging. >>>> >>>> It is designed to allow debugging traces of kvm to be generated on >>>> Up/Smp machines. Each trace entry is outputted in a trace ring buffe= r >>>> for per cpu which is mapped to userspace, and the userspace tools ca= n >>>> analyze the data according to some formats definitions. >>>> >>>> Since we already have had debugfs_entries and some other kernel debu= g >>>> mechanism to use, does this kvmtrace make sense? Any comment is >>>> welcomed. =20 >>> This looks very useful. While kvm_stat provides good data, this is >>> much more in depth. >>> >>> The kernel already contains a method of transferring percpu data to >>> userspace; see Documentation/filesystems/relay.txt. It supports >>> mmap() and read(). Please see if it is a good fit. >>> =20 >> >> I would also suggest to use the new kernel standard for instrumentatio= n: >> trace_mark(). >> >> This would also allow to reuse the trace points with other tracer and >> maybe even obsolete a separate transportation channel, e.g. when LTTng= >> is once :-/ merged. >> =20 >=20 > Can one have markers automatically recorded? Or do you need to connect= > the marker with a logging function? Yes, of course you need a probe function. Either your own one, or one provided by other tracers. >=20 > If the latter, it's too difficult to use. I don't think it is. Check linux/samples/markers/probe-example.c. BTW, RCU-Trace (not yet mainlined) make use of markers as well, see -rt. And in contrast to the suggested implementation, markers have less impact on the code if built-in but disabled. So there would be no reasons for not shipping kvm production binaries that are prepared to be traced. But if you prefer the inlined version, I bet you'll have to hide it from reviewers at LKML. ;) Jan --------------enig9E64D967E6FE085C06DE6D01 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.4-svn0 (GNU/Linux) Comment: Using GnuPG with SUSE - http://enigmail.mozdev.org iD8DBQFH3Ub9niDOoMHTA+kRAmUWAJ4n+XqqAinmz8Vjwy3Cx15vsYm/PQCfW8mB smD55h8I1NK/H7c91J8bJL4= =PPXv -----END PGP SIGNATURE----- --------------enig9E64D967E6FE085C06DE6D01-- --===============1816343380== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ --===============1816343380== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel --===============1816343380==--