On 12.03.2015 22:31, Alireza Haghdoost wrote: > On Mon, Feb 23, 2015 at 12:32 PM, Alireza Haghdoost <alireza@xxxxxxxxxx> wrote: >> I needed to inject I/O completion latency in the RAID5/6 codes for >> test purpose. I was wondering where would be the good place in >> md/raid5.c code to add delay ? >> >> So far I have tried adding mdelay/udelay in raid5_end_write_request() >> and it seems it works to increase I/O completion of writes. However, >> adding delay in raid5_end_read_request() does not really change the >> read I/O latency. Any idea ? >> >> --Alireza > > Can Some one help me on this issue ? Everything comes through md_make_request() in drivers/md/md.c but there are multiple different bio->bi_end_io functions. We have implemented custom I/O latency measurement. I've posted the patch to this list some time ago. So feel free to look how it works as an inspiration. http://www.spinics.net/lists/raid/msg46525.html It introduces its own struct md_bio_private containing the original bi_end_io function pointer and introduces the md_bio_endio() function as a generic bi_end_io to be always called before calling the original bi_end_io function. I hope this helps! We've reworked this stuff since then a bit more but it's really beneficial to detect disks which became slow. Cheers, Sebastian -- 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
