All graphs for this bug:
  https://chromeperf.appspot.com/group_report?bug_id=606891

Original alerts at time of bug-filing:
  https://chromeperf.appspot.com/group_report?keys=agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICg5NyZ9QgM,agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICg5IKMrQsM


Bot(s) for this bug's original alert(s):

android-nexus5X
android-nexus7v2

=== Auto-CCing suspected CL author vmpstr@chromium.org ===

Hi vmpstr@chromium.org, the bisect results pointed to your CL below as possibly
causing a regression. Please have a look at this info and see whether
your CL be related.


===== BISECT JOB RESULTS =====
Status: completed


===== SUSPECTED CL(s) =====
Subject : (Reland) content: Enable image decode tasks on android.
Author  : vmpstr
Commit description:
  
This patch enables image decode tasks on android.

R=enne@chromium.org, sievers@chromium.org

Review URL: https://codereview.chromium.org/1903973004

Cr-Commit-Position: refs/heads/master@{#389579}
Commit  : 6c0b5111741a42f7f4abc0d839c074bedde118a8
Date    : Mon Apr 25 22:14:43 2016


===== TESTED REVISIONS =====
Revision                Mean Value  Std. Dev.   Num Values  Good?
chromium@389560         211.99673   1.484985    5           good
chromium@389578         213.70552   0.676149    5           good
chromium@389579         256.42096   0.685407    5           bad         <-
chromium@389580         256.99125   1.28514     5           bad
chromium@389581         257.30748   1.085728    5           bad
chromium@389583         257.74655   1.470751    5           bad
chromium@389587         260.48525   2.640974    5           bad
chromium@389596         261.96168   2.073868    5           bad

Bisect job ran on: android_nexus7_perf_bisect
Bug ID: 606891

Test Command: src/tools/perf/run_benchmark -v --browser=android-chromium --output-format=chartjson --upload-results --also-run-disabled-tests image_decoding.image_decoding_measurement
Test Metric: ImageDecoding_avg/ImageDecoding_avg
Relative Change: 23.57%
Score: 99.9

Buildbot stdio: http://build.chromium.org/p/tryserver.chromium.perf/builders/android_nexus7_perf_bisect/builds/2939
Job details: https://chromeperf.appspot.com/buildbucket_job_status/9014291670356540096


Not what you expected? We'll investigate and get back to you!
  https://chromeperf.appspot.com/bad_bisect?try_job_id=5801928454307840

| O O | Visit http://www.chromium.org/developers/speed-infra/perf-bug-faq
|  X  | for more information addressing perf regression bugs. For feedback,
| / \ | file a bug with component Tests>AutoBisect.  Thank you!

based on bisect reults, vmpstr@ could you please check the issue.

Yep, I'll take a look.

It turns out to be the difference in memory reuse is the cause of this issue:

Before image decodes, the pixel ref (and discardable memory) for an original decode would be stored on the bitmap itself. The process of decoding this would first clear the memory, which would take about 60ms on the first run. 

When that bitmap is deleted, we would delete the discardable memory. When we create it again in the test, the discardable memory happens to hand out the exactly same memory. The second clear now only takes 2ms. I assume this is due to some clever caching on the cpu. 



Now, with image decodes, the original decode is stored independently of the image. So, this means that when the image is destroyed, we still hold on to the (unlocked) discardable memory and when it's recreated, we create a new discardable memory block always and the clear is always 60ms. 

I think this is just a artifact of the test and unlikely to be a common case in the wild. I would recommend a WontFix here.

enne@, wdyt?

Yeah, I think in practice this won't ever happen.

Marking WontFix as per #5.

===== BISECT JOB RESULTS =====
Status: completed


===== SUSPECTED CL(s) =====
Subject : (Reland) content: Enable image decode tasks on android.
Author  : vmpstr
Commit description:
  
This patch enables image decode tasks on android.

R=enne@chromium.org, sievers@chromium.org

Review URL: https://codereview.chromium.org/1903973004

Cr-Commit-Position: refs/heads/master@{#389579}
Commit  : 6c0b5111741a42f7f4abc0d839c074bedde118a8
Date    : Mon Apr 25 22:14:43 2016


===== TESTED REVISIONS =====
Revision         Mean     Std Dev   N  Good?
chromium@389402  77.8462  0.684596  5  good
chromium@389555  75.7226  0.414688  5  good
chromium@389574  75.551   0.372117  5  good
chromium@389577  75.4708  0.844309  5  good
chromium@389578  75.6249  0.272612  5  good
chromium@389579  175.093  0.648626  5  bad    <--
chromium@389584  174.689  0.586437  5  bad
chromium@389593  175.649  1.34583   5  bad
chromium@389631  175.744  1.17834   5  bad
chromium@389707  175.384  0.635955  5  bad
chromium@390011  173.932  1.30994   5  bad
chromium@390620  174.27   0.65655   5  bad
chromium@391837  176.918  0.719709  5  bad

Bisect job ran on: android_s5_perf_bisect
Bug ID: 606891

Test Command: src/tools/perf/run_benchmark -v --browser=android-chromium --output-format=chartjson --upload-results --also-run-disabled-tests image_decoding.image_decoding_measurement
Test Metric: ImageDecoding_avg/image_decoding.html?jpg
Relative Change: 127.27%
Score: 99.9

Buildbot stdio: http://build.chromium.org/p/tryserver.chromium.perf/builders/android_s5_perf_bisect/builds/651
Job details: https://chromeperf.appspot.com/buildbucket_job_status/9013032836839949776


Not what you expected? We'll investigate and get back to you!
  https://chromeperf.appspot.com/bad_bisect?try_job_id=5263346836701184

| O O | Visit http://www.chromium.org/developers/speed-infra/perf-bug-faq
|  X  | for more information addressing perf regression bugs. For feedback,
| / \ | file a bug with component Tests>AutoBisect.  Thank you!

===== BISECT JOB RESULTS =====
Status: completed


===== SUSPECTED CL(s) =====
Subject : (Reland) content: Enable image decode tasks on android.
Author  : vmpstr
Commit description:
  
This patch enables image decode tasks on android.

R=enne@chromium.org, sievers@chromium.org

Review URL: https://codereview.chromium.org/1903973004

Cr-Commit-Position: refs/heads/master@{#389579}
Commit  : 6c0b5111741a42f7f4abc0d839c074bedde118a8
Date    : Mon Apr 25 22:14:43 2016


===== TESTED REVISIONS =====
Revision         Mean     Std Dev   N  Good?
chromium@389402  75.3993  0.417735  5  good
chromium@389555  74.918   0.759633  5  good
chromium@389574  75.4362  0.443295  5  good
chromium@389577  75.4111  0.692046  5  good
chromium@389578  75.7505  0.906417  5  good
chromium@389579  175.133  1.5535    5  bad    <--
chromium@389584  175.71   1.32157   5  bad
chromium@389593  175.16   1.31702   5  bad
chromium@389631  175.251  0.895545  5  bad
chromium@389707  175.245  1.30477   5  bad
chromium@390011  174.111  0.765935  5  bad
chromium@390620  174.597  1.45298   5  bad
chromium@391837  176.654  0.639581  5  bad

Bisect job ran on: android_s5_perf_bisect
Bug ID: 606891

Test Command: src/tools/perf/run_benchmark -v --browser=android-chromium --output-format=chartjson --upload-results --also-run-disabled-tests image_decoding.image_decoding_measurement
Test Metric: ImageDecoding_avg/image_decoding.html?jpg
Relative Change: 134.29%
Score: 99.9

Buildbot stdio: http://build.chromium.org/p/tryserver.chromium.perf/builders/android_s5_perf_bisect/builds/652
Job details: https://chromeperf.appspot.com/buildbucket_job_status/9013032767723427344


Not what you expected? We'll investigate and get back to you!
  https://chromeperf.appspot.com/bad_bisect?try_job_id=5861525319843840

| O O | Visit http://www.chromium.org/developers/speed-infra/perf-bug-faq
|  X  | for more information addressing perf regression bugs. For feedback,
| / \ | file a bug with component Tests>AutoBisect.  Thank you!