2012/8/8 Jianpeng Ma <majianpeng@xxxxxxxxx>: > On 2012-08-08 10:58 Shaohua Li <shli@xxxxxxxxxx> Wrote: >>2012/8/7 Jianpeng Ma <majianpeng@xxxxxxxxx>: >>> On 2012-08-07 13:32 Shaohua Li <shli@xxxxxxxxxx> Wrote: >>>>2012/8/7 Jianpeng Ma <majianpeng@xxxxxxxxx>: >>>>> On 2012-08-07 11:22 Shaohua Li <shli@xxxxxxxxxx> Wrote: >>>>>>My directIO randomwrite 4k workload shows a 10~20% regression caused by commit >>>>>>895e3c5c58a80bb. directIO usually is random IO and if request size isn't big >>>>>>(which is the common case), delay handling of the stripe hasn't any advantages. >>>>>>For big size request, delay can still reduce IO. >>>>>> >>>>>>Signed-off-by: Shaohua Li <shli@xxxxxxxxxxxx> >>> [snip] >>>>>>-- >>>>> May be used size to judge is not a good method. >>>>> I firstly sended this patch, only want to control direct-write-block,not for reqular file. >>>>> Because i think if someone used direct-write-block for raid5,he should know the feature of raid5 and he can control >>>>> for write to full-write. >>>>> But at that time, i did know how to differentiate between regular file and block-device. >>>>> I thik we should do something to do this. >>>> >>>>I don't think it's possible user can control his write to be a >>>>full-write even for >>>>raw disk IO. Why regular file and block device io matters here? >>>> >>>>Thanks, >>>>Shaohua >>> Another problem is the size. How to judge the size is large or not? >>> A syscall write is a dio and a dio may be split more bios. >>> For my workload, i usualy write chunk-size. >>> But your patch is judge by bio-size. >> >>I'd ignore workload which does sequential directIO, though >>your workload is, but I bet no real workloads are. So I'd like > Sorry,my explain maybe not corcrect. I write data once which size is almost chunks-size * devices,in order to full-write > and as possible as to no pre-read operation. >>only to consider big size random directio. I agree the size >>judge is arbitrary. I can optimize it to be only consider stripe >>which hits two or more disks in one bio, but not sure if it's >>worthy doing. Not ware big size directio is common, and even >>is, big size request IOPS is low, a bit delay maybe not a big >>deal. > If add a acc_time for 'striep_head' to control? > When get_active_stripe() is ok, update acc_time. > For some time, stripe_head did not access and it shold pre-read. Do you want to add a timer for each stripe? This is even ugly. How do you choose the expire time? A time works for harddisk definitely will not work for a fast SSD. -- 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
