Martin Peschke wrote: > On Wed, 2008-07-16 at 10:22 -0400, Alan D. Brunelle wrote: >> Martin Peschke wrote: >>> Low-level device drivers might have additional data which complements >>> blktrace data. For example, zfcp, a SCSI HBA driver, is capable of >>> obtaining additional latency information per request from HBAs. Those >>> latencies allow to further break down the overall D2C request latency >>> provided by blktrace. >>> >>> We propose an additional trace for blktrace, called "driver data". It is >>> a sort of small binary blob, which contains a low-level driver specific >>> struct. Blktrace would be able to filter this trace (-a option) and >>> include it within its binary output. A small device driver specific tool >>> on top of blktrace would then analyze "driver data" traces. >>> >>> Patch 1/3 makes the blktrace kernel code provide blk_add_driver_data() >>> for use by device drivers. >>> >>> Patch 2/3 adds support for driver data traces to blktrace tools. >>> >>> Patch 3/3 makes zfcp provide additional request latency and queue >>> utilization data through blktrace. >>> >>> >>> Patches are against scsi-misc and blktrace git. >>> >>> >>> Martin >> Hi Martin - >> >> Have you thought about just using blk_add_trace_msg instead? > > Hi Alan, > good point. Yes, we thought about it. It actually inspired > blk_add_drv_data(). > > blk_add_trace_msg adds information to the textual output of blkparse. > There is no point in forwarding it to the binary output. > > We need the opposite. We want driver data to show up in binary ouput. > But there is no point in blkparse trying to generate some ascii message > from low-level device driver specific data. > > Besides this would lead us down the path of parsing textual output for > our monitoring tool. This would burn more CPU than a c-program which > consumes binary data. > > Martin > > Hm, again, if the blktrace | blkiomon (direct, no blkparse) is how you do things, I would think that it would /not/ take all that much processing power to parse character strings. (I've heard that IBM makes some pretty fast processors... :-) ) In particular, if you make the character strings more machine readable (no text, just numbers) for example it's just some atoi's going on. Alan -- 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
