[LU-487] procfs stats file incorrectly records brw_read and brw_write values

• Status: Resolved
• Project: Lustre
• Affects Version/s: Lustre 2.1.0, Lustre 1.8.6
• Fix Version/s: Lustre 2.1.0
• Type: Bug
• Priority: Minor
• Reporter: Richard Henwood (Inactive)
• Assignee: Richard Henwood (Inactive)
• Resolution: Fixed
• Severity: 3
• Epic: papercut

Description

brw_read in llite client procfs stats file claims to measure in units of pages. For example:

# cat /proc/fs/lustre/llite/lustre-ffff88000449a800/stats
snapshot_time             1308264214.464257 secs.usecs
dirty_pages_hits          1419716 samples [regs]
dirty_pages_misses        833472 samples [regs]
read_bytes                322963 samples [bytes] 1 2684356 154236888794
write_bytes               225001 samples [bytes] 0 125912 3323679002
brw_read                  15285 samples [pages] 4096 4096 62607360

However, in ./lustre/llite/lloop.c the tallying of the LPROC_LL_BRW_WRITE/READ counter increments by the value of:

page_count << PAGE_CACHE_SHIFT

Using this value has the effect of not measure pages, but the total bytes of the pages. A simple fix maybe to remove the PAGE_CACHE_SHIFT. Or, rename '[pages]' to '[bytes]' in the output.

Comments

[Andreas Dilger]

Since the "read_bytes" and "write_bytes" entries already exist, it makes sense to remove the "<< PAGE_CACHE_SHIFT" and actually count in pages. It is also inconsistent that there is a brw_read stat, but not a brw_write stat...

[Richard Henwood (Inactive)]

Can I query:

Since this tally call is in lloop.c, it is only used during loopback testing.

If this is the case, the stats brw_ records are the number of partial page request that took place during testing.

so: brw_ in it's current state of limited use.

[Richard Henwood (Inactive)]

So, to call out explicitly:

It seems to me brw_ records can lead to miss-interpretation in their current state.

How about omitting them entirely?

[Richard Henwood (Inactive)]

change available at:

http://review.whamcloud.com/#change,1056

[Build Master (Inactive)]

Integrated in lustre-master » x86_64,client,el5,ofa #244
LU-487 brw_[read|write] stats to correctly counts number of pages.

Oleg Drokin : 6aea71f39238f370c02a2f293a01555cc653bd01
Files :

• lustre/llite/lloop.c

[Build Master (Inactive)]

Integrated in lustre-master » x86_64,client,el5,inkernel #244
LU-487 brw_[read|write] stats to correctly counts number of pages.

Oleg Drokin : 6aea71f39238f370c02a2f293a01555cc653bd01
Files :

• lustre/llite/lloop.c

[Build Master (Inactive)]

Integrated in lustre-master » i686,client,el6,inkernel #244
LU-487 brw_[read|write] stats to correctly counts number of pages.

Oleg Drokin : 6aea71f39238f370c02a2f293a01555cc653bd01
Files :

• lustre/llite/lloop.c

[Build Master (Inactive)]

Integrated in lustre-master » i686,client,el5,inkernel #244
LU-487 brw_[read|write] stats to correctly counts number of pages.

Oleg Drokin : 6aea71f39238f370c02a2f293a01555cc653bd01
Files :

• lustre/llite/lloop.c

[Build Master (Inactive)]

Integrated in lustre-master » x86_64,server,el6,inkernel #244
LU-487 brw_[read|write] stats to correctly counts number of pages.

Oleg Drokin : 6aea71f39238f370c02a2f293a01555cc653bd01
Files :

• lustre/llite/lloop.c

[Build Master (Inactive)]

Integrated in lustre-master » x86_64,client,sles11,inkernel #244
LU-487 brw_[read|write] stats to correctly counts number of pages.

Oleg Drokin : 6aea71f39238f370c02a2f293a01555cc653bd01
Files :

• lustre/llite/lloop.c

[Build Master (Inactive)]

Integrated in lustre-master » x86_64,client,el6,inkernel #244
LU-487 brw_[read|write] stats to correctly counts number of pages.

Oleg Drokin : 6aea71f39238f370c02a2f293a01555cc653bd01
Files :

• lustre/llite/lloop.c

[Build Master (Inactive)]

Integrated in lustre-master » x86_64,server,el5,ofa #244
LU-487 brw_[read|write] stats to correctly counts number of pages.

Oleg Drokin : 6aea71f39238f370c02a2f293a01555cc653bd01
Files :

• lustre/llite/lloop.c

[Build Master (Inactive)]

Integrated in lustre-master » x86_64,client,ubuntu1004,inkernel #244
LU-487 brw_[read|write] stats to correctly counts number of pages.

Oleg Drokin : 6aea71f39238f370c02a2f293a01555cc653bd01
Files :

• lustre/llite/lloop.c

[Build Master (Inactive)]

Integrated in lustre-master » x86_64,server,el5,inkernel #244
LU-487 brw_[read|write] stats to correctly counts number of pages.

Oleg Drokin : 6aea71f39238f370c02a2f293a01555cc653bd01
Files :

• lustre/llite/lloop.c

[Build Master (Inactive)]

Integrated in lustre-master » i686,server,el5,ofa #244
LU-487 brw_[read|write] stats to correctly counts number of pages.

Oleg Drokin : 6aea71f39238f370c02a2f293a01555cc653bd01
Files :

• lustre/llite/lloop.c

[Build Master (Inactive)]

Integrated in lustre-master » i686,server,el5,inkernel #244
LU-487 brw_[read|write] stats to correctly counts number of pages.

Oleg Drokin : 6aea71f39238f370c02a2f293a01555cc653bd01
Files :

• lustre/llite/lloop.c

[Build Master (Inactive)]

Integrated in lustre-master » i686,server,el6,inkernel #244
LU-487 brw_[read|write] stats to correctly counts number of pages.

Oleg Drokin : 6aea71f39238f370c02a2f293a01555cc653bd01
Files :

• lustre/llite/lloop.c

[Build Master (Inactive)]

Integrated in lustre-master » i686,client,el5,ofa #244
LU-487 brw_[read|write] stats to correctly counts number of pages.

Oleg Drokin : 6aea71f39238f370c02a2f293a01555cc653bd01
Files :

• lustre/llite/lloop.c

[Richard Henwood (Inactive)]

Fix merged into Master.