Re: [zfs-discuss] ZFS ARC Hits By App

2010-02-14 Thread Sanjeev 
Abdullah,

On Thu, Feb 11, 2010 at 03:42:38PM -0500, Abdullah Al-Dahlawi wrote:
 Hi Sanjeev
 
 linking the application to the ARCSTAT_BUMP(arcstat_hits) is not
 straightforward and time consuming especially if I am running many
 experiments.
 
 Brendan has commented on on the post by providing an alternative DTrace
 script , here is his post ...
 --
 dtrace -n 'sdt:::arc-hit { @[execname] = count(); }'
 
 Or to filter just on firefox:
 
  dtrace -n 'sdt:::arc-hit /execname == firefox-bin/ { @ = count(); }'
 
 If neither of them work, it just means that that particular sdt provider
 probe wasn't available, and we can get this information from using the fbt
 provider instead.
 
 Note: ZFS prefetch is pretty effective, so streaming reads from disk will
 often
 show up as arc hits since ZFS has put the data in cache before the
 application
 reads it.  Which is the intent.
 
 I ran Brendan script while watching arcstat from kstat and notice great deal
 of discrepancy in terms of cache hits  misses numbers between kstat 
 Brendan's scrip. I am not sure exactly where 'sdt' probe collects the cache
 hits information !!.

The DTrace probe which collects the info is right above the location that I
mentioned. Look for lines similar to : DTRACE_PROBE1(arc__hit, arc_buf_hdr_t 
*, hdr);
in zfs/arc.c.

The script which Brendan has mentioned tracks only those which are caused by the
application that you are tracking. Whereas, kstat values are for the entire arc.
Hence, they would be completely different (kstat numbers would be much higher).
Are you noticing this pattern or is it something else ?

Thanks and regards,
Sanjeev

 On Wed, Feb 10, 2010 at 11:43 PM, Sanjeev sanjeev.bagew...@sun.com wrote:
 
  Abdullah,
 
  On Tue, Feb 09, 2010 at 02:12:24PM -0500, Abdullah Al-Dahlawi wrote:
   Greeting ALL
  
   I am wondering if it is possible to monitor the ZFS ARC cache hits using
   DTRACE. In orher words, would be possible to know how many ARC cache hits
   have been resulted by a particular application such as firefox ??
 
  ZFS has kstat for a whole bunch of these. You could run kstat -m zfs and
  see
  if which ones help you.
 
  Correlating these stats to a particular application would be a little
  difficult.
 
  Using Dtrace, you could track down the read/write operations and see if
  they
  lead to a hit/miss in ARC. Take a look at the routine arc_read here :
 
  http://src.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/uts/common/fs/zfs/arc.c
 
  ARCSTAT_BUMP(arcstat_hits); is the routine which increments the hit
  count.
 
  You could track arc_read()s called from the context of the application and
  check
  if it causes a hit or a miss.
 
  Thanks and regards,
  Sanjeev
  
   Your response is highly appreciated.
  
  
   Thanks
  
  
   --
   Abdullah
   dahl...@ieee.org
   (IM) ieee2...@hotmail.com
   
   Check The Fastest 500 Super Computers Worldwide
   http://www.top500.org/list/2009/11/100
 
 
  --
  
  Sanjeev Bagewadi
  Solaris RPE
  Bangalore, India
 
 
 
 
 -- 
 Abdullah Al-Dahlawi
 http://www.google.com/profiles/aldahlawi
 
 Check The Fastest 500 Super Computers Worldwide
 http://www.top500.org/list/2009/11/100

-- 

Sanjeev Bagewadi
Solaris RPE 
Bangalore, India
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Re: [zfs-discuss] ZFS ARC Hits By App

2010-02-11 Thread Abdullah Al-Dahlawi 
Hi Sanjeev

linking the application to the ARCSTAT_BUMP(arcstat_hits) is not
straightforward and time consuming especially if I am running many
experiments.

Brendan has commented on on the post by providing an alternative DTrace
script , here is his post ...
--
dtrace -n 'sdt:::arc-hit { @[execname] = count(); }'

Or to filter just on firefox:

 dtrace -n 'sdt:::arc-hit /execname == firefox-bin/ { @ = count(); }'

If neither of them work, it just means that that particular sdt provider
probe wasn't available, and we can get this information from using the fbt
provider instead.

Note: ZFS prefetch is pretty effective, so streaming reads from disk will
often
show up as arc hits since ZFS has put the data in cache before the
application
reads it.  Which is the intent.

I ran Brendan script while watching arcstat from kstat and notice great deal
of discrepancy in terms of cache hits  misses numbers between kstat 
Brendan's scrip. I am not sure exactly where 'sdt' probe collects the cache
hits information !!.

Any feed back ?




On Wed, Feb 10, 2010 at 11:43 PM, Sanjeev sanjeev.bagew...@sun.com wrote:

 Abdullah,

 On Tue, Feb 09, 2010 at 02:12:24PM -0500, Abdullah Al-Dahlawi wrote:
  Greeting ALL
 
  I am wondering if it is possible to monitor the ZFS ARC cache hits using
  DTRACE. In orher words, would be possible to know how many ARC cache hits
  have been resulted by a particular application such as firefox ??

 ZFS has kstat for a whole bunch of these. You could run kstat -m zfs and
 see
 if which ones help you.

 Correlating these stats to a particular application would be a little
 difficult.

 Using Dtrace, you could track down the read/write operations and see if
 they
 lead to a hit/miss in ARC. Take a look at the routine arc_read here :

 http://src.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/uts/common/fs/zfs/arc.c

 ARCSTAT_BUMP(arcstat_hits); is the routine which increments the hit
 count.

 You could track arc_read()s called from the context of the application and
 check
 if it causes a hit or a miss.

 Thanks and regards,
 Sanjeev
 
  Your response is highly appreciated.
 
 
  Thanks
 
 
  --
  Abdullah
  dahl...@ieee.org
  (IM) ieee2...@hotmail.com
  
  Check The Fastest 500 Super Computers Worldwide
  http://www.top500.org/list/2009/11/100


 --
 
 Sanjeev Bagewadi
 Solaris RPE
 Bangalore, India




-- 
Abdullah Al-Dahlawi
http://www.google.com/profiles/aldahlawi

Check The Fastest 500 Super Computers Worldwide
http://www.top500.org/list/2009/11/100
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Re: [zfs-discuss] ZFS ARC Hits By App

2010-02-10 Thread Sanjeev 
Abdullah,

On Tue, Feb 09, 2010 at 02:12:24PM -0500, Abdullah Al-Dahlawi wrote:
 Greeting ALL
 
 I am wondering if it is possible to monitor the ZFS ARC cache hits using
 DTRACE. In orher words, would be possible to know how many ARC cache hits
 have been resulted by a particular application such as firefox ??

ZFS has kstat for a whole bunch of these. You could run kstat -m zfs and see
if which ones help you.

Correlating these stats to a particular application would be a little difficult.

Using Dtrace, you could track down the read/write operations and see if they
lead to a hit/miss in ARC. Take a look at the routine arc_read here :
http://src.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/uts/common/fs/zfs/arc.c

ARCSTAT_BUMP(arcstat_hits); is the routine which increments the hit count.

You could track arc_read()s called from the context of the application and check
if it causes a hit or a miss. 

Thanks and regards,
Sanjeev
 
 Your response is highly appreciated.
 
 
 Thanks
 
 
 -- 
 Abdullah
 dahl...@ieee.org
 (IM) ieee2...@hotmail.com
 
 Check The Fastest 500 Super Computers Worldwide
 http://www.top500.org/list/2009/11/100


-- 

Sanjeev Bagewadi
Solaris RPE 
Bangalore, India
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[zfs-discuss] ZFS ARC Hits By App

2010-02-09 Thread Abdullah Al-Dahlawi 
Greeting ALL

I am wondering if it is possible to monitor the ZFS ARC cache hits using
DTRACE. In orher words, would be possible to know how many ARC cache hits
have been resulted by a particular application such as firefox ??

Your response is highly appreciated.


Thanks


-- 
Abdullah
dahl...@ieee.org
(IM) ieee2...@hotmail.com

Check The Fastest 500 Super Computers Worldwide
http://www.top500.org/list/2009/11/100
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