From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Subject: Re: RAID456 direct I/O write performance Date: Tue, 9 Sep 2014 13:24:31 +1000 Message-ID: <20140909132431.24456db1@notabene.brown> References: <12EF8D94C6F8734FB2FF37B9FBEDD17358642FF8@EXCHANGE.collogia.de> <12EF8D94C6F8734FB2FF37B9FBEDD17358643012@EXCHANGE.collogia.de> <5408D5CC.101@shiftmail.org> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; boundary="Sig_//m.OM8fCq8W4gglo1zoj+Fg"; protocol="application/pgp-signature" Return-path: In-Reply-To: <5408D5CC.101@shiftmail.org> Sender: linux-raid-owner@vger.kernel.org To: Ethan Wilson Cc: "linux-raid@vger.kernel.org" List-Id: linux-raid.ids --Sig_//m.OM8fCq8W4gglo1zoj+Fg Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Thu, 04 Sep 2014 23:12:44 +0200 Ethan Wilson wrote: > OTOH I would like to ask kernel experts one thing if I may: does anybody= =20 > know a way to get a stack trace for a process which is currently running= =20 > in kernel mode and is running NOW on a CPU and it is not stopped waiting= =20 > in a queue? I know about /proc/pid/stack but that one shows=20 > 0xffffffffffffffff for such a case. Being able to do that would help to=20 > answer the above question too... The contents of the stack would change while it was being inspected, so it would be impossible to get a meaningful trace. Maybe you could disable all but one CPU. Then whenever you try to look at the stack of another process it must have scheduled and so will have a stable visible stack... Or maybe you would use "perf record -g" to get some stack information, I'm not sure. NeilBrown --Sig_//m.OM8fCq8W4gglo1zoj+Fg Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) iQIVAwUBVA5y7znsnt1WYoG5AQKAAQ//c3Ag0bKH0E94ohnd8ABrw7wn4+NNEjyn O9YOBrR/+1r7L+MY0mO3KiangjNBbyZBoyFHMp9kEW41f5G3iCnmx66QI2YoOAcH KLMX79wVxl2Alc9CHGjaVHkmaMXZkUIDIqqIU3jEj5VlIR9GT+Z3eV4pTVauMAQ3 0Abpqs+eYwDN+mS6edLbHZRNXwLz9p2hz2V/fBz+fugksn1MZYN0K3mSxAV78kIC iI7bhVtgPopdAOoPZTte08yME0zyd4ThJE5YCCpL74o9FTwuwtSRtLAKuLgmofCh HgUBhSO0mejcd2m+/0ua1VnKM42b5q6vwBoNR644onlQn+eVLCfu+ToHVRIktq5k ZXku9kGlGwTqc1WnstI94GAVDCWNcPkUpCcdGLzx8PNnUOe90gx7ffWRWFQ1mj3g jeFTkAjVqSaWfunH8yUcb0/+1jD7Hi12ktf32N1gMX9GL+pA958I0n9Yq7zqXbXK ZrZ3gpjnl95ClwjX9hs5xKEj8g4F7vAcZZejysPI/cyfO/uZQxpUkRSLeqUWE5jb NdZHmP2AfZjc+xda1oifazqW0+/xNS0Ekq+vM4OoAJXKAtxdH0HPf2pCTZSNo/vP jI1vtXa0X5frNSaj7NLWFvrL+29EqS0tsmfGBT9HPLkrEv8VVjHaBwyeKWGlyHHU cyecp2L/svU= =4FP7 -----END PGP SIGNATURE----- --Sig_//m.OM8fCq8W4gglo1zoj+Fg--