Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755296Ab0DTUwh (ORCPT ); Tue, 20 Apr 2010 16:52:37 -0400 Received: from smtp-out.google.com ([216.239.44.51]:38548 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755214Ab0DTUwg convert rfc822-to-8bit (ORCPT ); Tue, 20 Apr 2010 16:52:36 -0400 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=mime-version:in-reply-to:references:date:message-id:subject:from:to: cc:content-type:content-transfer-encoding:x-system-of-record; b=LYza2YBLdqFuK9MiyLSaZURub1m8IDmxsYBi3yVjUjYqCoI9XkRiWwx1i9dLIw9xZ KDlQ7eX79JbZByhISZIMA== MIME-Version: 1.0 In-Reply-To: References: Date: Tue, 20 Apr 2010 13:52:21 -0700 Message-ID: Subject: Re: [PATCH] 2.6.34-rc3 v2 Disable R_OK (Early ACK) on SII 3726 PMP From: Grant Grundler To: Linux IDE mailing list Cc: Jeff Garzik , Tejun Heo , LKML Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5044 Lines: 108 ping? Can this patch please be applied? I was assuming this will show up here: http://git.kernel.org/?p=linux/kernel/git/jgarzik/libata-dev.git;a=shortlog;h=refs/heads/upstream-linus thanks, grant On Wed, Apr 14, 2010 at 6:43 PM, Grant Grundler wrote: > In 2009, While running "cache read" performance test of drives behind > SII PMP we encountered a "all 5 drives" timeout on more than 30% of the > machines under test.  This patch reduces the rate by a factor of about 70. > Low enough that we didn't care to further investigate the issue. > > Performance impact with any sort of "normal" use was ~2%+ CPU and less > than 1% throughput degradation.  Worst case impact (cached read) was > 6% IOPS reduction. This is with NCQ off (q=1) but I believe FIS based > switching enabled in the SATA driver. > > The patch disables "Early ACK" in the 3726 port multiplier. > "Early ACK" is issued when device sends a FIS to the host (via PMP) > and the PMP sends an ACK immediately back to the device - well before > the host gets the response. Under worst case IOPs load (cached read > test) and more than 2 PMPs connected to a 4-port SATA controller, > I suspect the time to service all of the PMPs is exceeding the PMPs > ability to keep track of outstanding FIS it owes the Host. Reducing > the number of PMPs to 2 (or 1) reduces the frequency by several orders > of magnitude. Kudos to Gwendal for initial debugging of this issue. > [Any errors in the description are mine, not his.] > > Patch is currently in production on Google servers. > > Signed-off-by: Grant Grundler > Signed-off-by: Gwendal Grignou > Acked-by: Tejun Heo > > --- > > v2: dropped references to 4726 since I didn't test 4726, >    moved register definition directly into libata-pmp.c, and >    expanded the comment in the code to summarize the above description. > > Code below is white space mangled. Please use attached file. > > diff --git a/drivers/ata/libata-pmp.c b/drivers/ata/libata-pmp.c > index 00305f4..487227a 100644 > --- a/drivers/ata/libata-pmp.c > +++ b/drivers/ata/libata-pmp.c > @@ -231,10 +231,14 @@ static const char *sata_pmp_spec_rev_str(const u32 *gscr) >        return ""; >  } > > +#define PMP_GSCR_SII_POL 129 > + >  static int sata_pmp_configure(struct ata_device *dev, int print_info) >  { >        struct ata_port *ap = dev->link->ap; >        u32 *gscr = dev->gscr; > +       u16 vendor = sata_pmp_gscr_vendor(gscr); > +       u16 devid = sata_pmp_gscr_devid(gscr); >        unsigned int err_mask = 0; >        const char *reason; >        int nr_ports, rc; > @@ -260,12 +264,34 @@ static int sata_pmp_configure(struct ata_device > *dev, int print_info) >                goto fail; >        } > > +       /* Disable sending Early R_OK. > +        * With "cached read" HDD testing and multiple ports busy on a SATA > +        * host controller, 3726 PMP will very rarely drop a deferred > +        * R_OK that was intended for the host. Symptom will be all > +        * 5 drives under test will timeout, get reset, and recover. > +        */ > +       if (vendor == 0x1095 && devid == 0x3726) { > +               u32 reg; > + > +               err_mask = sata_pmp_read(&ap->link, PMP_GSCR_SII_POL, ®); > +               if (err_mask) { > +                       rc = -EIO; > +                       reason = "failed to read Sil3726 Private Register"; > +                       goto fail; > +               } > +               reg &= ~0x1; > +               err_mask = sata_pmp_write(&ap->link, PMP_GSCR_SII_POL, reg); > +               if (err_mask) { > +                       rc = -EIO; > +                       reason = "failed to write Sil3726 Private Register"; > +                       goto fail; > +               } > +       } > + >        if (print_info) { >                ata_dev_printk(dev, KERN_INFO, "Port Multiplier %s, " >                               "0x%04x:0x%04x r%d, %d ports, feat 0x%x/0x%x\n", > -                              sata_pmp_spec_rev_str(gscr), > -                              sata_pmp_gscr_vendor(gscr), > -                              sata_pmp_gscr_devid(gscr), > +                              sata_pmp_spec_rev_str(gscr), vendor, devid, >                               sata_pmp_gscr_rev(gscr), >                               nr_ports, gscr[SATA_PMP_GSCR_FEAT_EN], >                               gscr[SATA_PMP_GSCR_FEAT]); > -- 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/