From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Reinecke Subject: Re: [PATCH v2.5 3/6] scsi_debug: add multiple queue support Date: Mon, 2 May 2016 10:35:53 +0200 Message-ID: <57271169.8020204@suse.de> References: <1462070687-12689-1-git-send-email-dgilbert@interlog.com> <1462070687-12689-4-git-send-email-dgilbert@interlog.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from mx2.suse.de ([195.135.220.15]:51880 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752317AbcEBIf4 (ORCPT ); Mon, 2 May 2016 04:35:56 -0400 In-Reply-To: <1462070687-12689-4-git-send-email-dgilbert@interlog.com> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Douglas Gilbert , linux-scsi@vger.kernel.org Cc: martin.petersen@oracle.com, tomas.winkler@intel.com, emilne@redhat.com, bart.vanassche@sandisk.com On 05/01/2016 04:44 AM, Douglas Gilbert wrote: > Add submit_queue parameter (minimum and default: 1; maximum: > nr_cpu_ids) that controls how many queues are built, each with > their own lock and in_use bit vector. Add statistics parameter > which is default on. >=20 > Signed-off-by: Douglas Gilbert > --- > drivers/scsi/scsi_debug.c | 680 +++++++++++++++++++++++++++++-------= ---------- > 1 file changed, 426 insertions(+), 254 deletions(-) >=20 Two general questions for this: - Why do you get rid of the embedded command payload? Where's the benefit of allocating the commands yourself? - Wouldn't it be better to move to a per-cpu structure per queue? Each queue will be tacked to a CPU anyway, so you could be using per-cpu structures. Otherwise you'll run into synchronization issues, and any performance gain you might get from scsi-mq is lost as you to synchronize on the lower level. Cheers, Hannes --=20 Dr. Hannes Reinecke Teamlead Storage & Networking hare@suse.de +49 911 74053 688 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 N=FCrnberg GF: F. Imend=F6rffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton HRB 21284 (AG N=FCrnberg) -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html