Recent concurrency improvements in the AHCI driver and CAM need testing
naoya.sugioka at gmail.com
Sun Apr 10 23:41:12 PDT 2011
This is happened before your recent update, but my laptop showing
on ahci0.1 when io_acpi is enabled. This timeout prevents to complete
I just wonder this is happened because ahci.0.1 is associated to ATAPI
(DVD-RW) drive without
ahci0.1: Found ATAPI "TSSTcorp DVD+/-RW TS-U633F D200" serial="R3476GSSA81272"
ahci0.1: tags=0/32 satacap=0202 satafea=0068 NCQ=NO capacity=1.00MB
ahci0.1: f85=0000 f86=0000 f87=4000 WC=notsupp RA=notsupp SEC=notsupp
then start showing a timeout message.
Let me know if you need further information, thank you.
On Sat, Apr 9, 2011 at 9:00 PM, Matthew Dillon
<dillon at apollo.backplane.com> wrote:
> I've pushed some serious changes to the AHCI SATA driver and CAM.
> One fixes issues where the tags were not being utilized to their fullest
> extent... well, really they weren't being utilized at all. I'm not
> sure how I missed the problem before, but it is fixed now.
> The second ensures that read requests cannot saturate all available
> tags and cause writes to stall, and vise-versa, and also separates
> out the read and write BIO streams and treats them as separate entities,
> which means that reads can continue to be dispatched even if writes
> saturate the drive's cache and writes can continue to be dispatched
> even if concurrent read(s) would otherwise eat all available tags.
> The reason the read/write saturation fixes are important is because
> writes are usually completed instantly since they just go to the drive
> cache, so even if reads are saturated there's no reason not to push
> writes to the drive. Plus when the HD's cache becomes saturated writes
> no longer complete instantly and would prevent reads from being
> dispatched if all the tags were used to hold the writes.
> With these fixes I am getting much better numbers with concurrency
> I now get around 37000 IOPS doing random 512-byte sector reads with
> a Crucial C300 SSD, verses ~8000 or so before the fix.
> And I now get around ~365 IOPS with the same test on a hard drive,
> verses ~150 IOPS before (remember these are random reads!).
> blogbench also appears to have much better write/read parallelism
> against the swapcache with the SSD/HD combo. Memory caches blow
> out at around blog #1300 on my test boxes.
> With the changes blogbench write performance is maintained through
> blog #1600 or so, without the changes it drops off at #1300.
> With the changes the swapcache SSD is pushing ~1400 IOPS or so
> satisfying random read requests. Without the changes the swapcache
> SSD is only pushing ~130 IOPS.
> With the changes blogbench is able to maintain a ~60000 article
> read rate at the end of the test. Without the changes the
> read rate is more around ~10000 at the end of the test. At this
> stage swapcache has cached a significant chunk of the data
> in the SSD so the I/O activity is mixed random SSD and HD reads.
> Ok, so I feel a bit sheepish that I missed the fact that the AHCI
> driver wasn't utilizing its tags properly before. The difference
> in performance is phenominal. Maybe we will start winning some
> of those I/O benchmark tests now.
> Matthew Dillon
> <dillon at backplane.com>
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