Kent Overstreet <koverstreet@...> writes: > > Sounds like a good portion of your IO is bypassing the cache. That > will happen if some of it's sequential, or if the SSD latency goes > over a threshold - sequential_cutoff, congested_read_threshold_us and > congest_write_threshold_us (if I'm remembering the names correctly) > are the settings that control all that. 0 disables all of them. > So I set the sequential_cutoff and congested_read_threshold_us to both be 0. Since I was only doing reads, I figured there was no need to mess with the write option. But, I'm still seeing a problem. My hardware is: 1 - Dell PowerEdge R710 w/ 24 x Xeon processors, 96GB of ram 2 - Micron P320H SSD 3 - LSI storage device connected by a SAS interface What I see is that when I do random reads over a 10GB region, the cache warms up but hits a read response plateau at about 7ms. I still see a LOT (i.e. 32000 IOPS) of I/O to the disk. Yes, if I run the same test over a 1GB region, runs really fast. Pretty close to the max IOPS rate of the SSD. So I'm thinking there is a problem here or I have a bcache config issue. I'm willing to try things but I need some guidance on what to look for as it seems like a bcache issue. Thanks for the help. -brad w. -- To unsubscribe from this list: send the line "unsubscribe linux-bcache" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
