Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757696Ab3CFLVe (ORCPT ); Wed, 6 Mar 2013 06:21:34 -0500 Received: from mx1.redhat.com ([209.132.183.28]:47246 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757401Ab3CFLVa (ORCPT ); Wed, 6 Mar 2013 06:21:30 -0500 Date: Wed, 6 Mar 2013 12:26:12 +0100 From: Alexander Gordeev To: Jeff Garzik Cc: linux-kernel@vger.kernel.org, linux-ide@vger.kernel.org Subject: [PATCH RFC 0/1] AHCI: Optimize interrupt processing Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3872 Lines: 101 Hi Jeff, As I am not sure about my reading of the statistics and the trade-off I identified (below), this patch a RFC. The numbers are taken by running 'if=/dev/sd{a,b,c} of=/dev/null' All time values is in us. Before this update host lock average holdtime was 3.266532061 and average waittime was 0.009832679 [1]. After the update average holdtime (slightly) rose up to 0.335267418 while average waittime decreased to 0.000320469 [2]. Which means host lock with local interrupt disabled is held roughly the same while the average waittime dropped 30 times. After this update port events are handled with local interrupts enabled and compete on individual per-port locks with average holdtime 1.540987475 and average waittime 0.000714864 [3]. Comparing to [1], ata_scsi_queuecmd() holds port locks 2 times less and waits for locks 13 times less. The downside of this change is introduction of a kernel thread and (supposedly) increased total average time of handling a AHCI interrupt - at most 1.5 times. The upside is better access times from ata_scsi_queuecmd() to port locks and moving port interrupt handling out of the hardware interrupt context. Thanks! Lock usage statistics. 1. ahci_interrupt vs ata_scsi_queuecmd (host->lock) Test holdtime-total waittime-total acquisitions holdtime-avg waittime-avg # 01. 22732497.77 93399.89 06393367 3.555637862 0.014608874 02. 20358052.08 52869.72 06454133 3.154265969 0.008191607 03. 20322516.57 54981.40 06459318 3.146232554 0.008511951 04. 18558686.89 39178.05 06469468 2.868657344 0.006055838 05. 19069799.90 31961.00 06455953 2.953831897 0.004950625 06. 23783542.56 97159.79 06387322 3.723554654 0.015211350 07. 23889266.74 102625.45 06386666 3.740491007 0.016068705 08. 19284522.61 32655.91 06450568 2.989585198 0.005062486 ----------- ----------- avg 3.266532061 0.009832679 2. ahci_single_irq_intr vs ahci_port_thread_fn (host->lock) Test holdtime-total waittime-total acquisitions holdtime-avg waittime-avg # 01. 7572820.95 08414.47 21614279 0.350361951 0.000389301 02. 7029942.02 02992.88 21680248 0.324255609 0.000138046 03. 7298791.32 05974.01 21701755 0.336322630 0.000275278 04. 7077621.26 04360.66 21745564 0.325474256 0.000275278 05. 7606619.38 12158.88 21832248 0.348412100 0.000556923 06. 7605174.70 12205.41 21828021 0.348413386 0.000559162 07. 7058514.97 03701.46 21740632 0.324669263 0.000170255 08. 7039641.91 04331.74 21711867 0.324230151 0.000199510 ----------- ----------- avg 0.335267418 0.000320469 3. ahci_port_thread_fn vs ata_scsi_queuecmd (pp->lock) Test holdtime-total waittime-total acquisitions holdtime-avg waittime-avg # 01. 38531452.56 24236.62 21752844 1.771329421 0.001114182 02. 00024050.92 00005.84 00015999 1.503276455 0.000365023 03. 34071257.07 09699.50 21829593 1.560782973 0.000444328 04. 00019086.10 00001.37 00016054 1.188868818 0.000085337 05. 36535324.31 20676.43 21949439 1.664522009 0.000942003 06. 37433608.34 22942.34 21945295 1.705769202 0.001045433 07. 31456091.88 19895.22 21862170 1.438836670 0.000910030 08. 32628001.94 17739.99 21831844 1.494514249 0.000812574 ----------- ----------- avg 1.540987475 0.000714864 Alexander Gordeev (1): AHCI: Optimize interrupt processing drivers/ata/acard-ahci.c | 8 ++--- drivers/ata/ahci.c | 54 ++++++++++++++++++------------- drivers/ata/ahci.h | 10 +++-- drivers/ata/ahci_platform.c | 3 +- drivers/ata/libahci.c | 74 +++++++++++++++++++++++++------------------ 5 files changed, 85 insertions(+), 64 deletions(-) -- 1.7.7.6 -- Regards, Alexander Gordeev agordeev@redhat.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/