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 <grundler@xxxxxxxxxx> 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 <grundler@xxxxxxxxxx> > Signed-off-by: Gwendal Grignou <gwendal@xxxxxxxxxx> > Acked-by: Tejun Heo <tj@xxxxxxxxxx> > > --- > > 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 "<unknown>"; > } > > +#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-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
