2012/3/20 Holger Kiehl <Holger.Kiehl@xxxxxx>: > Hello, > > > On Tue, 20 Mar 2012, Shaohua Li wrote: > >> 2012/3/20 Holger Kiehl <Holger.Kiehl@xxxxxx>: >>> >>> Hello, >>> >>> >>> On Fri, 16 Mar 2012, Shaohua Li wrote: >>> >>>> The patches add TRIM support for raid linear/0/1/10. I'll add TRIM >>>> support >>>> for >>>> raid 4/5/6 later. The implementation is pretty straightforward and >>>> self-explained. >>>> >>>> v1->v2: >>>> 1. fixed a checking issue >>>> 2. dropped discard request plug and replace it with no discard merege, >>>> because >>>> current SCSI layer can't handle discard request merge. >>>> >>> Have tested TRIM patches on three different systems with the following >>> hardware/ setup: >>> >>> 1) root mounted on a raid1 over two SAS SSD's (200GB) and /home >>> partition >>> on a raid0 over a fusionio ioDrive Duo. Is very new and seen very >>> little usage. >>> >>> 2) root and /home mounted on a raid0 over two Intel X25 Postville >>> (160GB) connected to a Intel P55 Express chipset. Has seen very >>> heavy usage for approx. 2 years. >>> >>> 3) root and /home mounted on a raid0 over three OCZ-VERTEX2 (120GB) >>> connected via ICH7 south bridge. Has seen mild usage for approx. >>> 1.5 years. >>> >>> Made the following observations when running my own benchmark which >>> copies around a lot of small files and deletes them. The benchmark on >>> all systems was always run only on the /home partition ie. on a raid0. >>> >>> For system 1) there is hardly any measurable differnce whether discard >>> is enabled or not (~29000 files per second). >>> >>> On system 2) the performance drops from 6500->3700 files per second, >>> but under normal usage one does not notice any difference. >> >> do you have the blktrace data when the benchmark is running, especially >> when doing file deletion. I'd like to check the latency of discard in this >> case. >> > It is uploaded on ftp://ftp.dwd.de/pub/afd/test/trim Thanks, I'll check it. >>> System 3) has problems during boot, it is so slow that some operations >>> receive a timeout during boot: >>> >>> udevd[474]: timeout '/sbin/blkid -o udev -p /dev/md0' >>> udevd[474]: timeout: killing '/sbin/blkid -o udev -p /dev/md0' [866] >>> systemd[1]: dev-md3.swap activation timed out. Stopping. >> >> In this one, discard request is slow. And per SATA standard, discard >> request >> can't be parallel, so only one request one time, which further slows it >> down. >> > Ok, so having three disc in a raid 0 is even worth. > > >>> Even removing discard does not help and the above errors happen during >>> boot and booting takes a long time. >> >> this doesn't make sense. If you don't mount with discard option, no >> discard request >> is issued. >> > I read some where that swap uses discard by default and if I remember > correctly it initializes the whole swap area at boot. So doing that > over three disks might explain why I get those timeout error messages > and after boot these commands work without delay. This looks a bug to me. if swapon doesn't add discard option, we shouldn't do discard. Let me post a patch, and see how people think. Thanks, Shaohua -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
