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no slat log

DISCUSSION Dennis Jacobfeuerborn 3 participants 5 messages Aug 6, 2013 – Aug 8, 2013

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#0 lore raw

Hi,
when I try to create logs with fio I get bw, iops, lat, clat and slat logs but the slat log always has a size of 0 bytes. Is this a bug or is data for this log only generated with specific options for fio?

Regards,
Dennis

#1 lore raw
Quoted 3 lines · Dennis Jacobfeuerborn

Hi,
when I try to create logs with fio I get bw, iops, lat, clat and slat logs but the slat log always has a size of 0 bytes. Is this a bug or is data for this log only generated with specific options for fio?

Dennis,

I've been trying this on my 2.1.2 with the following job :

[read-sda-4k-para]
bs=4k
filename=/dev/sda
rw=read
write_lat_log=lat.log

On my side, the slat file is perfectly filled.

Can you provide a testing procedure & the version you use ?

Cheers,

#2 lore raw
Quoted 16 lines · Erwan Velu
Quoted 5 lines · Dennis Jacobfeuerborn

Hi,
when I try to create logs with fio I get bw, iops, lat, clat and slat logs but the slat log always has a size of 0 bytes. Is this a bug or is data for this log only generated with specific options for fio?

Dennis,

I've been trying this on my 2.1.2 with the following job :

[read-sda-4k-para]
bs=4k
filename=/dev/sda
rw=read
write_lat_log=lat.log

Quoted 3 lines

On my side, the slat file is perfectly filled.

Can you provide a testing procedure & the version you use ?

I just tested the job above and these are the files produced:

[dennis@nexus fio]$ ls -l
total 11272

-rw-r--r--. 1 root   root   5767080  7. Aug 12:31 lat.log_clat.log
-rw-r--r--. 1 root   root   5767087  7. Aug 12:31 lat.log_lat.log
-rw-r--r--. 1 root   root         0  7. Aug 12:31 lat.log_slat.log
-rw-rw-r--. 1 dennis dennis      84  7. Aug 12:31 logtest.fio

There are not errors or warnings during the fio run so it's not clear why the file ends up being empty.

Regards,
Dennis

#3 lore raw
Quoted 11 lines · Dennis Jacobfeuerborn

I just tested the job above and these are the files produced:

[dennis@nexus fio]$ ls -l
total 11272

(quoted diff) +0 -4
-rw-r--r--. 1 root   root   5767080  7. Aug 12:31 lat.log_clat.log
-rw-r--r--. 1 root   root   5767087  7. Aug 12:31 lat.log_lat.log
-rw-r--r--. 1 root   root         0  7. Aug 12:31 lat.log_slat.log
-rw-rw-r--. 1 dennis dennis      84  7. Aug 12:31 logtest.fio

There are not errors or warnings during the fio run so it's not clear why the file ends up being empty.

Are you running 2.1.2 ?
If so, can you provides the complete output of fio while running ?

Cheers,

#4 lore raw
In reply to Dennis Jacobfeuerborn
Quoted 30 lines · Dennis Jacobfeuerborn
Quoted 16 lines · Erwan Velu
Quoted 5 lines · Dennis Jacobfeuerborn

Hi,
when I try to create logs with fio I get bw, iops, lat, clat and slat logs but the slat log always has a size of 0 bytes. Is this a bug or is data for this log only generated with specific options for fio?

Dennis,

I've been trying this on my 2.1.2 with the following job :

[read-sda-4k-para]
bs=4k
filename=/dev/sda
rw=read
write_lat_log=lat.log

Quoted 3 lines

On my side, the slat file is perfectly filled.

Can you provide a testing procedure & the version you use ?

I just tested the job above and these are the files produced:

[dennis@nexus fio]$ ls -l
total 11272

(quoted diff) +0 -4
-rw-r--r--. 1 root   root   5767080  7. Aug 12:31 lat.log_clat.log
-rw-r--r--. 1 root   root   5767087  7. Aug 12:31 lat.log_lat.log
-rw-r--r--. 1 root   root         0  7. Aug 12:31 lat.log_slat.log
-rw-rw-r--. 1 dennis dennis      84  7. Aug 12:31 logtest.fio
Quoted 2 lines

There are not errors or warnings during the fio run so it's not clear why the file ends up being empty.

slat only exists for async IO engines. For a sync workload, submission and completion retrieval are not separate events, so you cannot do split submission + completion stats.

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Jens Axboe