On 2011-01-11 07:48, Tao Ma wrote: > From: Tao Ma <boyu.mt@xxxxxxxxxx> > > With the newest kernel(say 2.6.37, some older one should also have the > similar problem), some cfq messages are added to blktrace, so it makes > the old blkparse broken. > > See a simple example: > 1. blktrace /dev/sdb -o -|blkparse -i - > 2. Run the following command(/dev/sdb1 is mounted at /mnt/test_dir): > dd if=/mnt/test_dir/test of=/dev/null bs=4k count=1 iflag=direct > > There are only 2 lines of output there: > 8,16 0 1 0.000000000 13183 A R 114759 + 8 <- (8,17) 114696 > 8,16 0 2 0.000000491 13183 Q R 114759 + 8 [dd] > > And even we run a command line like: > for((i=0;i<100;i++))do dd if=/mnt/ocfs2/test of=/dev/null bs=4k count=1 iflag=direct;done > We are only given the same 2 lines of output. > > While the really one should look like: > 8,16 0 1 0.000000000 13319 A R 114759 + 8 <- (8,17) 114696 > 8,16 0 2 0.000000376 13319 Q R 114759 + 8 [dd] > 8,16 0 0 0.000005931 0 m N cfq13319 alloced > 8,16 0 3 0.000006259 13319 G R 114759 + 8 [dd] > 8,16 0 4 0.000007143 13319 P N [dd] > 8,16 0 5 0.000007817 13319 I R 114759 + 8 [dd] > 8,16 0 0 0.000008491 0 m N cfq13319 insert_request > 8,16 0 0 0.000009029 0 m N cfq13319 add_to_rr > ... > > The main reason is that in show_entries_rb, we test sequences every time, > but actually with some messages like cfq, the sequence number is always > 0 which makes the old sequence check refuses all the logs after it. > So only check/store sequence number if it isn't a message. Thanks for the patch with the nice and detailed description, I have applied it. But I'm curious, this is a 2.6.37 regression? -- Jens Axboe -- 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
