Re: accuracy of btt result on btreplay?
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Updates. I decreased/increased max-pkts to 1/16, however nothing changed, still less merges in the replay run. I think the "S" attribute for "write" should be the reason. First I suspected the "S" attribute is brought by io_submit system call, however I tested aio-stress tool which uses io_submit to send AIO also. In the gathering traces, the write operations doesn't have "S" attribute, however during replay, the "S" attribute happened again. So I wonder where the "S" comes from? Does anyone have suggestions? Thanks in advance. Thx, Xuekun On Thu, Mar 4, 2010 at 9:37 AM, Xuekun Hu <xuekun.hu@xxxxxxxxx> wrote: > Hi, Alan > > It should be no changes on the system. > > I compared the per io dump info, and found the merges did decrease a > lot. Another interesting thing I found from the blkparse output is the > write requests has much more "WS" (synchronous) flag in the replay > run. Does the merges decrease due to the "S" flag? > > Perhaps I need to tune the "-max-pkts"? In my case, to increase its > value to let more requests have more opportunities to merge? > > BTW. I also tried replaying "dd" traces, and found the number of > merges also decreases. > > Thx, Xuekun > -- To unsubscribe from this list: send the line "unsubscribe linux-btrace" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html