base: Avoid purging more discardable memory than necessary.

base: Avoid purging more discardable memory than necessary.

In situations when discardable memory usage is above the limit,
instead of purging the amount of memory that we would try to
reclaim under moderate memory pressure, purge only what is
necessary to stay below the limit.

This simplifies the code and makes it easier to understand how
memory is purged as a result of reaching the memory limit.

BUG=237681
TEST=base_unittests --gtest_filter=DiscardableMemoryProviderPermutationTests/DiscardableMemoryProviderPermutationTest.LRUDiscardedAmount/*

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=234652

[reveman, 2013-11-05 23:17:13]

I think this simplifies the code a bit and makes it easier to reason with how
memory is purged as a result of reaching the memory limit. Please take a look.

[Ian Vollick, 2013-11-06 14:35:13]

On 2013/11/05 23:17:13, David Reveman wrote:
> I think this simplifies the code a bit and makes it easier to reason with how
> memory is purged as a result of reaching the memory limit. Please take a look.

lgtm.

[reveman, 2013-11-11 20:28:52]

ping

[willchan no longer on Chromium, 2013-11-12 17:22:59]

Reviewing now. First thing...please update the CL description to explain why
this change is being made. I think maybe your first mail explains this.

[willchan no longer on Chromium, 2013-11-12 17:34:25]

lgtm

https://codereview.chromium.org/59083011/diff/1/base/memory/discardable_memor...
File base/memory/discardable_memory_provider.h (right):

https://codereview.chromium.org/59083011/diff/1/base/memory/discardable_memor...
base/memory/discardable_memory_provider.h:114: //
|bytes_to_reclaim_under_moderate_pressure_|.
Maybe we should add better comments here since you've changed the implementation
but the function comments didn't change.

[reveman, 2013-11-12 20:38:11]

Updated description and comment.

https://codereview.chromium.org/59083011/diff/1/base/memory/discardable_memor...
File base/memory/discardable_memory_provider.h (right):

https://codereview.chromium.org/59083011/diff/1/base/memory/discardable_memor...
base/memory/discardable_memory_provider.h:114: //
|bytes_to_reclaim_under_moderate_pressure_|.
On 2013/11/12 17:34:26, willchan wrote:
> Maybe we should add better comments here since you've changed the
implementation
> but the function comments didn't change.

Done.

[commit-bot: I haz the power, 2013-11-12 20:42:23]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/reveman@chromium.org/59083011/90001

[commit-bot: I haz the power, 2013-11-12 22:43:25]

Change committed as 234652