Indan Zupancic wrote: >> Can you try to measure with sd_resume in place? > > [ 2.173366] sd 0:0:0:0: [sda] Starting disk > [ 2.475422] ata2: SATA link down (SStatus 0 SControl 310) > [ 5.478403] ata1: SATA link up 1.5 Gbps (SStatus 113 SControl 310) > [ 5.481928] ata1.00: ata_hpa_resize 1: sectors = 234441648, hpa_sectors = 234441648 > [ 5.485904] ata1.00: ata_hpa_resize 1: sectors = 234441648, hpa_sectors = 234441648 > [ 5.485913] ata1.00: configured for UDMA/100 > [ 5.505109] sd 0:0:0:0: [sda] 234441648 512-byte hardware sectors (120034 MB) > [ 5.505461] sd 0:0:0:0: [sda] Write Protect is off > [ 5.505465] sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00 > [ 5.505612] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or > FUA > ... > [ 6.157259] Restarting tasks ... done. > > > And with echo 0 > /sys/class/scsi_disk/0\:0\:0\:0/manage_start_stop: > > [ 2.476476] ata2: SATA link down (SStatus 0 SControl 310) > ... > [ 2.825479] Restarting tasks ... done. > ... > [ 5.022076] ata1: SATA link up 1.5 Gbps (SStatus 113 SControl 310) > [ 5.025605] ata1.00: ata_hpa_resize 1: sectors = 234441648, hpa_sectors = 234441648 > [ 5.028594] ata1.00: ata_hpa_resize 1: sectors = 234441648, hpa_sectors = 234441648 > [ 5.028606] ata1.00: configured for UDMA/100 > [ 5.028720] sd 0:0:0:0: [sda] 234441648 512-byte hardware sectors (120034 MB) > [ 5.028767] sd 0:0:0:0: [sda] Write Protect is off > [ 5.028773] sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00 > [ 5.028831] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or > FUA > > So over all it takes half a second longer to detect the disk, but > because everything waits on it, it takes more than three seconds > longer to resume. Eeeek. Extra three secs doesn't sound too hot. :-( > Setting manage_start_stop to 0 fixes it and is good enough for me, I > didn't notice anything bad yet because of the unmanaged > stop. Implementing background spin up will fix it too. Just commenting out sd_resume() would be a better solution for your case tho. >>> Everything seems to work fine without sd_resume(), so why is it needed? >> Because not all disks spin up without being told to do so and like it or >> not spinning disks up on resume is the default behavior. As I wrote in >> the other reply, it would be worthwhile to make it configurable. > > Not even after they receive a read command? Ugh. After receiving a command which requires media access, they do. What I was saying is that the current default behavior is to spin up all devices on resume and part of that is achieved by sd_resume(). Hmmm... skipping START_STOP during sd_resume() actually is a pretty good solution for ATA devices. I'll think about it. Thanks. -- tejun - 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
