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Re: Poor performance using discard

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: Poor performance using discard
From: Thomas Lynema <lyz27@xxxxxxxxx>
Date: Fri, 02 Mar 2012 09:57:00 -0500
Cc: xfs@xxxxxxxxxxx
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In-reply-to: <1330658311.6438.24.camel@core24>
References: <1330469778.9688.7.camel@core24> <20120229012259.GW3592@dastard> <1330480826.9688.23.camel@core24> <20120229040819.GZ3592@dastard> <1330658311.6438.24.camel@core24>
> > Also, I think you need to provide a block trace (output of
> > blktrace/blkparse for the rm -rf workloads) for both the XFS and
> > ext4 cases so we can see what discards are actually being issued and
> > how long they take to complete....
> 

Partial xfs results attached this was the overall summary with xfs.

The summary looks like this.

CPU0 (xfs.trace):
 Reads Queued:       1,274,    9,216KiB  Writes Queued:       9,981,
156,710KiB
 Read Dispatches:    1,738,    8,656KiB  Write Dispatches:    9,855,
157,818KiB
 Reads Requeued:       495               Writes Requeued:        72
 Reads Completed:    1,844,   12,916KiB  Writes Completed:   15,486,
8,360KiB
 Read Merges:            0,        0KiB  Write Merges:           42,
364KiB
 Read depth:            10               Write depth:            11
 IO unplugs:            95               Timer unplugs:           3
CPU1 (xfs.trace):
 Reads Queued:         153,    1,372KiB  Writes Queued:      14,521,
183,608KiB
 Read Dispatches:      235,    2,348KiB  Write Dispatches:   15,246,
183,627KiB
 Reads Requeued:        24               Writes Requeued:       748
 Reads Completed:      197,    1,868KiB  Writes Completed:   14,885,
11,825KiB
 Read Merges:            0,        0KiB  Write Merges:           19,
60KiB
 Read depth:            10               Write depth:            11
 IO unplugs:            39               Timer unplugs:           7
CPU2 (xfs.trace):
 Reads Queued:       1,156,    7,520KiB  Writes Queued:      10,873,
160,987KiB
 Read Dispatches:    1,586,    7,416KiB  Write Dispatches:   10,724,
160,687KiB
 Reads Requeued:       446               Writes Requeued:        69
 Reads Completed:      586,    3,820KiB  Writes Completed:    5,310,
4,103KiB
 Read Merges:            0,        0KiB  Write Merges:           57,
664KiB
 Read depth:            10               Write depth:            11
 IO unplugs:            54               Timer unplugs:           8
CPU3 (xfs.trace):
 Reads Queued:         126,    1,436KiB  Writes Queued:       5,197,
47,004KiB
 Read Dispatches:      135,    1,124KiB  Write Dispatches:    5,388,
46,187KiB
 Reads Requeued:        20               Writes Requeued:       333
 Reads Completed:       82,      940KiB  Writes Completed:    5,037,
1,551KiB
 Read Merges:            0,        0KiB  Write Merges:           91,
708KiB
 Read depth:            10               Write depth:            11
 IO unplugs:            50               Timer unplugs:           8

Total (xfs.trace):
 Reads Queued:       2,709,   19,544KiB  Writes Queued:      40,572,
548,309KiB
 Read Dispatches:    3,694,   19,544KiB  Write Dispatches:   41,213,
548,319KiB
 Reads Requeued:       985               Writes Requeued:     1,222
 Reads Completed:    2,709,   19,544KiB  Writes Completed:   40,718,
25,839KiB
 Read Merges:            0,        0KiB  Write Merges:          209,
1,796KiB
 IO unplugs:           238               Timer unplugs:          26

Throughput (R/W): 45KiB/s / 60KiB/s
Events (xfs.trace): 309,109 entries
Skips: 0 forward (0 -   0.0%)

CPU0 (xfs.trace):
 Reads Queued:       1,274,    9,216KiB  Writes Queued:       9,981,
156,710KiB
 Read Dispatches:    1,738,    8,656KiB  Write Dispatches:    9,855,
157,818KiB
 Reads Requeued:       495               Writes Requeued:        72
 Reads Completed:    1,844,   12,916KiB  Writes Completed:   15,486,
8,360KiB
 Read Merges:            0,        0KiB  Write Merges:           42,
364KiB
 Read depth:            10               Write depth:            11
 IO unplugs:            95               Timer unplugs:           3
CPU1 (xfs.trace):
 Reads Queued:         153,    1,372KiB  Writes Queued:      14,521,
183,608KiB
 Read Dispatches:      235,    2,348KiB  Write Dispatches:   15,246,
183,627KiB
 Reads Requeued:        24               Writes Requeued:       748
 Reads Completed:      197,    1,868KiB  Writes Completed:   14,885,
11,825KiB
 Read Merges:            0,        0KiB  Write Merges:           19,
60KiB
 Read depth:            10               Write depth:            11
 IO unplugs:            39               Timer unplugs:           7
CPU2 (xfs.trace):
 Reads Queued:       1,156,    7,520KiB  Writes Queued:      10,873,
160,987KiB
 Read Dispatches:    1,586,    7,416KiB  Write Dispatches:   10,724,
160,687KiB
 Reads Requeued:       446               Writes Requeued:        69
 Reads Completed:      586,    3,820KiB  Writes Completed:    5,310,
4,103KiB
 Read Merges:            0,        0KiB  Write Merges:           57,
664KiB
 Read depth:            10               Write depth:            11
 IO unplugs:            54               Timer unplugs:           8
CPU3 (xfs.trace):
 Reads Queued:         126,    1,436KiB  Writes Queued:       5,197,
47,004KiB
 Read Dispatches:      135,    1,124KiB  Write Dispatches:    5,388,
46,187KiB
 Reads Requeued:        20               Writes Requeued:       333
 Reads Completed:       82,      940KiB  Writes Completed:    5,037,
1,551KiB
 Read Merges:            0,        0KiB  Write Merges:           91,
708KiB
 Read depth:            10               Write depth:            11
 IO unplugs:            50               Timer unplugs:           8

Total (xfs.trace):
 Reads Queued:       2,709,   19,544KiB  Writes Queued:      40,572,
548,309KiB
 Read Dispatches:    3,694,   19,544KiB  Write Dispatches:   41,213,
548,319KiB
 Reads Requeued:       985               Writes Requeued:     1,222
 Reads Completed:    2,709,   19,544KiB  Writes Completed:   40,718,
25,839KiB
 Read Merges:            0,        0KiB  Write Merges:          209,
1,796KiB
 IO unplugs:           238               Timer unplugs:          26

Throughput (R/W): 45KiB/s / 60KiB/s
Events (xfs.trace): 309,109 entries
Skips: 0 forward (0 -   0.0%)

CPU0 (xfs.trace):
 Reads Queued:       1,274,    9,216KiB  Writes Queued:       9,981,
156,710KiB
 Read Dispatches:    1,738,    8,656KiB  Write Dispatches:    9,855,
157,818KiB
 Reads Requeued:       495               Writes Requeued:        72
 Reads Completed:    1,844,   12,916KiB  Writes Completed:   15,486,
8,360KiB
 Read Merges:            0,        0KiB  Write Merges:           42,
364KiB
 Read depth:            10               Write depth:            11
 IO unplugs:            95               Timer unplugs:           3
CPU1 (xfs.trace):
 Reads Queued:         153,    1,372KiB  Writes Queued:      14,521,
183,608KiB
 Read Dispatches:      235,    2,348KiB  Write Dispatches:   15,246,
183,627KiB
 Reads Requeued:        24               Writes Requeued:       748
 Reads Completed:      197,    1,868KiB  Writes Completed:   14,885,
11,825KiB
 Read Merges:            0,        0KiB  Write Merges:           19,
60KiB
 Read depth:            10               Write depth:            11
 IO unplugs:            39               Timer unplugs:           7
CPU2 (xfs.trace):
 Reads Queued:       1,156,    7,520KiB  Writes Queued:      10,873,
160,987KiB
 Read Dispatches:    1,586,    7,416KiB  Write Dispatches:   10,724,
160,687KiB
 Reads Requeued:       446               Writes Requeued:        69
 Reads Completed:      586,    3,820KiB  Writes Completed:    5,310,
4,103KiB
 Read Merges:            0,        0KiB  Write Merges:           57,
664KiB
 Read depth:            10               Write depth:            11
 IO unplugs:            54               Timer unplugs:           8
CPU3 (xfs.trace):
 Reads Queued:         126,    1,436KiB  Writes Queued:       5,197,
47,004KiB
 Read Dispatches:      135,    1,124KiB  Write Dispatches:    5,388,
46,187KiB
 Reads Requeued:        20               Writes Requeued:       333
 Reads Completed:       82,      940KiB  Writes Completed:    5,037,
1,551KiB
 Read Merges:            0,        0KiB  Write Merges:           91,
708KiB
 Read depth:            10               Write depth:            11
 IO unplugs:            50               Timer unplugs:           8

Total (xfs.trace):
 Reads Queued:       2,709,   19,544KiB  Writes Queued:      40,572,
548,309KiB
 Read Dispatches:    3,694,   19,544KiB  Write Dispatches:   41,213,
548,319KiB
 Reads Requeued:       985               Writes Requeued:     1,222
 Reads Completed:    2,709,   19,544KiB  Writes Completed:   40,718,
25,839KiB
 Read Merges:            0,        0KiB  Write Merges:          209,
1,796KiB
 IO unplugs:           238               Timer unplugs:          26

Throughput (R/W): 45KiB/s / 60KiB/s
Events (xfs.trace): 309,109 entries
Skips: 0 forward (0 -   0.0%)

CPU0 (xfs.trace):
 Reads Queued:       1,274,    9,216KiB  Writes Queued:       9,981,
156,710KiB
 Read Dispatches:    1,738,    8,656KiB  Write Dispatches:    9,855,
157,818KiB
 Reads Requeued:       495               Writes Requeued:        72
 Reads Completed:    1,844,   12,916KiB  Writes Completed:   15,486,
8,360KiB
 Read Merges:            0,        0KiB  Write Merges:           42,
364KiB
 Read depth:            10               Write depth:            11
 IO unplugs:            95               Timer unplugs:           3
CPU1 (xfs.trace):
 Reads Queued:         153,    1,372KiB  Writes Queued:      14,521,
183,608KiB
 Read Dispatches:      235,    2,348KiB  Write Dispatches:   15,246,
183,627KiB
 Reads Requeued:        24               Writes Requeued:       748
 Reads Completed:      197,    1,868KiB  Writes Completed:   14,885,
11,825KiB
 Read Merges:            0,        0KiB  Write Merges:           19,
60KiB
 Read depth:            10               Write depth:            11
 IO unplugs:            39               Timer unplugs:           7
CPU2 (xfs.trace):
 Reads Queued:       1,156,    7,520KiB  Writes Queued:      10,873,
160,987KiB
 Read Dispatches:    1,586,    7,416KiB  Write Dispatches:   10,724,
160,687KiB
 Reads Requeued:       446               Writes Requeued:        69
 Reads Completed:      586,    3,820KiB  Writes Completed:    5,310,
4,103KiB
 Read Merges:            0,        0KiB  Write Merges:           57,
664KiB
 Read depth:            10               Write depth:            11
 IO unplugs:            54               Timer unplugs:           8
CPU3 (xfs.trace):
 Reads Queued:         126,    1,436KiB  Writes Queued:       5,197,
47,004KiB
 Read Dispatches:      135,    1,124KiB  Write Dispatches:    5,388,
46,187KiB
 Reads Requeued:        20               Writes Requeued:       333
 Reads Completed:       82,      940KiB  Writes Completed:    5,037,
1,551KiB
 Read Merges:            0,        0KiB  Write Merges:           91,
708KiB
 Read depth:            10               Write depth:            11
 IO unplugs:            50               Timer unplugs:           8

Total (xfs.trace):
 Reads Queued:       2,709,   19,544KiB  Writes Queued:      40,572,
548,309KiB
 Read Dispatches:    3,694,   19,544KiB  Write Dispatches:   41,213,
548,319KiB
 Reads Requeued:       985               Writes Requeued:     1,222
 Reads Completed:    2,709,   19,544KiB  Writes Completed:   40,718,
25,839KiB
 Read Merges:            0,        0KiB  Write Merges:          209,
1,796KiB
 IO unplugs:           238               Timer unplugs:          26

Throughput (R/W): 45KiB/s / 60KiB/s
Events (xfs.trace): 309,109 entries
Skips: 0 forward (0 -   0.0%)



>  
> 
> Thanks for the input and patience.  
> 
> ~tom
> 
> 

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