Hi,
I am running blktrace to analyze I/O during a workload run and
obtained seek, latency and Block numbers as well as per-I/O-dump.
I found some of the I/Os present in seek data to be missing in
per-I/O-dump file. I have checked the binary file from blkparse and it
seems
to be containing the missing I/O s.
We tried to debug the issue. We observed that in case of the missing
I/O s that the function handle_issue (in trace_issue.c) does not print
to the per-io-dump file. The reason is that in routine:
dip_alloc, __dip_find(device) does not return NULL but some of the
fields of dip_info is null.
Code snippet:
struct d_info *dip_alloc(__u32 device, struct io *iop)
{
struct d_info *dip = __dip_find(device);
if (dip == NULL) {
char str[256];
dip = malloc(sizeof(struct d_info));
memset(dip, 0, sizeof(*di
....
}
The snippets for missing I/Os in per-io-dump file and the
corresponding seek data files are as follows.
Seek_d2d_c.dat
31.497678158 0 w
31.497684314 8 w
31.498714725 14965272 r
31.528598546 -14965280 w This IO is present in per-io dump
file as well.
Following IOs in seek file, not present in per-io-dump
..................................................................
31.528613109 0 w
31.528622309 0 w
31.528630846 0 w
31.528634955 83160 w
31.528642355 0 w
31.528649434 20528 w
31.528657480 0 w
31.528662694 8 w
31.528670169 0 w
31.528677839 0 w
31.528684786 0 w
31.528691806 0 w
31.528698477 0 w
31.528705403 0 w
31.528709002 400584 w
31.530779561 0 w
31.530788126 8 w
31.530795686 0 w
31.530802527 0 w
31.530810438 0 w
31.530818504 0 w
31.530825749 0 w
31.530833630 0 w
31.530838950 202957448 w
31.530843604 32328 w
31.530850399 0 w
31.530852766 8 w
31.530859075 0 w
31.530867215 0 w
31.530873892 0 w
31.530880583 0 w
31.562825308 0 w
31.562840145 0 w
31.562852559 1122896 w
31.562858357 32864 w
31.562867654 8 w
31.562877654 0 w
31.562885449 0 w
31.562893685 0 w
31.562901334 0 w
31.562909789 0 w
31.562918216 0 w
31.562924928 0 w
31.562928089 556128 w
31.562934325 8 w
31.562942388 0 w
31.562949731 0 w
31.562949731 0 w
31.564311119 0 w
31.564320633 0 w
31.564328996 0 w
31.564336468 0 w
31.564345531 0 w
31.564350328 186288 w
31.564427881 -206584872 w
31.564434939 206563432 w
31.565417543 -205184024 w
31.565420857 11800 w
31.565422806 8 w
31.565430704 45240 w
31.565438653 256 w
31.565444983 0 w
31.565451475 8984 w
31.565457018 0 w
31.599583103 0 w
31.599595560 0 w
31.599597558 45024 w
31.599606906 0 w
31.599609723 16 w
31.599618273 0 w
31.599625903 0 w
31.599634923 0 w
31.599644617 0 w
31.599652935 0 w
31.599655424 264976 w
31.599662249 0 w
31.599669961 0 w
31.599677146 8 w
31.599685009 0 w
31.599691789 0 w
31.601868207 0 w
31.601882099 0 w
31.601890870 0 w
31.601893157 166704 w
31.601900850 0 w
31.601906925 0 w
31.601913350 8 w
31.601918948 0 w
31.601921613 262144 w
31.601926410 0 w
31.601931174 0 w
31.601935870 0 w
31.601940385 0 w
31.601943616 167472 w
31.601948108 0 w
31.601952759 0 w
...............................................................
31.603150381 13656752 r <== this IO is seen in the
per-io-dump file, so above IOs are not added in per-io dup file
Per-io-dump file snippet: sda.dump
---------------------------------
8,0 : 31.526714955 Q 2486689584+8
31.526715179 M 2486689584+8
31.528598546 D 2486688568+1024
31.667381793 C 2486688568+1024
8,0 : 31.526713995 Q 2486689576+8
31.526714192 M 2486689576+8
31.528598546 D 2486688568+1024
31.667381793 C 2486688568+1024
-----------------------------------------
8,0 : 31.603144313 Q 2501586080+8 <=== IO till
this is missing from the above IO at time stamp (D) 31.528598546
31.603147310 G 2501586080+8
31.603149032 I 2501586080+8
31.603150381 D 2501586080+8
31.705885488 C 2501586080+8
-----------------------------------------
8,0 : 31.706148511 Q 2501577624+8
31.706149871 G 2501577624+8
31.706150682 I 2501577624+8
31.706151614 D 2501577624+8
31.802181772 C 2501577624+8
-----------------------------------------
8,0 : 31.802552026 Q 2501552992+8
31.802554440 G 2501552992+8
31.802555441 I 2501552992+8
31.802557069 D 2501552992+8
31.895693951 C 2501552992+8
-----------------------------------------
8,0 : 31.895980338 Q 2501544664+8
31.895981860 G 2501544664+8
31.895982601 I 2501544664+8
31.895983806 D 2501544664+8
31.896308616 C 2501544664+8
-----------------------------------------
8,0 : 31.924516917 Q 2501552680+8
31.924521388 G 2501552680+8
31.924523914 I 2501552680+8
31.924526197 D 2501552680+8
31.924967038 C 2501552680+8
----------------------------------------------------
Please help me to understand this discrepancy.
Exact commands to generate seek file and per-io dump file
1. blkparse -i sda -d sda.bin
2. btt -i sda.bin -p sda.dump
3. btt -i sda.bin -s sda.seek
Thanks in advance
Anindita
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