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Architecture - Profiling Tools for IO

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Note: The content on this page reflects the state of design of a Lustre feature at a particular point in time and may contain outdated information.

Contents

Definitions

Ganglia - distributed monitoring system(http://ganglia.info/)

Background

The profiling tool should be the part of LRE, and it will also be used in ORNL to profile the I/O status of their XT4/XT3 cluster. We decided to implemented the whole profiling system based on Ganglia.

Use cases

Collect profile information Performance & Usuability collect I/O and other stats from servers or all nodes.
Analyse profile information Usuability generate some nice graph according to the profiling information
Output profile information Usuability Output these graph to the end user.

Collect profile information

Stats collection

Scenario: Collecting stats from the servers and clients.
goals Overhead & Usuability
details OST_Req_Handle_Info req_qdepth, req_active, req_waittime /proc/fs/lustre/ost/OSS/ost_io/stats (server load)
OST_Read/Write_Info ost read/write count from each client /proc/fs/lustre/ost/OSS/ost_io/req_history
Read/Write_Req_Info req detail information. (percentage of !M rpc)/proc/fs/lustre/obdfilter/lustre-OST0001/brw_stats
Client_Cache_Avaiblity client cache stats information/proc/fs/lustre/obdfilter/lustre-OSTXXXX/exports/NID@nettype/UUID/cur_grant(dirty)_bytes
Client_RPC_Frequency Client RPC stats /proc/fs/lustre/osc(mdc)/stats
MDS_OPS_Stats MDS stats ops /proc/fs/lustre/mds/stats
Ldlm_Stats /proc/fs/lustre/ldlm/services/ldlm_cbd/stats
Implementation constrains Collecting stats by garlia monitor daemon

Trace logs collection job

Scenario: Generating the trace logs on each nodes.
goals Usuability (Geting indivial call trace information)
details VFS trace call logs Get VFS trace logs with enable D_VFSTRACE on each clients.
Server RPC trace log Get OST RPC handler trace log with enable D_RPCTRACE on each OSTS.
Implementation constrains Enable/Disable trace log by garlia monitor daemon

Analyse profile information

items

ID Description
OST_Load Represent the OST load over the time
Client_IO_Efficiency Represent client I/O rpc effiency (1 MB RPC percentage)
Client_Cache_Stats Represent whether client cache(grant) is efficiency
Client_RPC Represent client RPC frequency
VFS_trace Individial VFS trace call execute time (different call has different color)
Server RPC trace Individial OST RPC handler time
Ldlm Stats Represent lock (enqueue)conflicts status over the time

graphs

graphs input x_axis y axis
OST_Load OST_Req_Handle_Info time req_qdepth + req_active, req_waittime
Client_OST_IO_Efficiency Read/Write_Req_Info time each size req percent
Client_Cache_Stats Client_Cache_Avaiblity time Client cache(grant) avaiblity.
Client_RPC Client_RPC_Frequency time read_req_read_count
ldlm stats ldlm_stats time lock blocking_ast handler count on server.
VFS trace info VFS trace logs time Individial VFS trace call execute time (different call has different color)
Server RPC trace OST RPC trace logs time Individial OST RPC handler time

Note: It will need trace log analyse tool to retrieve the exectue call time frome the trace log.

Output profile information

Output the those graphes we got by Ganglia PHP Web Frontend.

Implementation constraint

  1. Use current utilities and architecture as much as possible, and be available to use as soon as possible.
  2. Implement the whole profiling system based on Ganglia
  3. It should work with lustre 1.4 also (ORNL may be stuck here for a long time)
  4. Easily extensible - realize that we may want to add or remove some stats in the future.
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