On Thu, 28 Apr 2016, Shaohua Li wrote: > On Thu, Apr 28, 2016 at 08:00:22PM +0000, Holger Kiehl wrote: > > Hello, > > > > On Mon, 25 Apr 2016, Shaohua Li wrote: > > > > > blk_queue_split marks bio unmergeable, which makes sense for normal bio. > > > But if dispatching the bio to underlayer disk, the blk_queue_split > > > checks are invalid, hence it's possible the bio becomes mergeable. > > > > > > In the reported bug, this bug causes trim against raid0 performance slash > > > https://bugzilla.kernel.org/show_bug.cgi?id=117051 > > > > > This patch makes a huge difference. On a system with two Samsung 850 Pro > > in a MD Raid0 setup the time for fstrim went down from ~30min to 18sec! > > > > However, on another system with two Intel P3700 1.6TB NVMe PCIe SSD's > > also setup as one big MD Raid0, the patch does not make any difference > > at all. fstrim takes more then 4 hours! > > Does the raid0 cross two partitions or two SSD? > Two SSD's. Where it works, for the two Samsung 850 Pro SATA SSD it was via partitions. > can you post blktrace data in the bugzilloa, I'll track the bug there. > I did the blktrace on the two md raid0 devices /dev/nvme[01]n1 for 2 minutes and attached them to the bug 117051 as a tar.bz2 file: https://bugzilla.kernel.org/show_bug.cgi?id=117051 Please just ask if I have forgotten anything. And many thanks for looking at this and all the good work! Regards, Holger -- 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
