Disk cache: Extend the internal buffering performed by each entry...

Disk cache: Extend the internal buffering performed by each entry
to cover external files.

We now keep a variable-size buffer and use it even after we
know that the data is not going to be stored by a block-file.
The backend keeps track of the total memory used by all entries
and prevents that value from going over a max value that
depends on the total memory available.

This CL removes the tests that were checking the synchronous
operation of sparse IO because that model is no longer supported
by the public API, and this CL would add complexity to them
(they fail due to thread safety concerns).

BUG=6626
TEST=net_unittests


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=57082

[rvargas (doing something else), 2010-08-17 23:21:19]

I think the simplest thing is to start with entry_impl.cc... everything else is
a consequence of that change.

http://codereview.chromium.org/3167020/diff/1/7
File net/disk_cache/entry_impl.cc (right):

http://codereview.chromium.org/3167020/diff/1/7#newcode1000
net/disk_cache/entry_impl.cc:1000: if (truncate)
I'd suggest not paying too much attention to the old version of this method and
the next one because the logic changed.

[Paweł Hajdan Jr., 2010-08-17 23:47:34]

Drive-by with a test comment. No need to wait for another review by me.

http://codereview.chromium.org/3167020/diff/1/4
File net/disk_cache/backend_unittest.cc (right):

http://codereview.chromium.org/3167020/diff/1/4#newcode1764
net/disk_cache/backend_unittest.cc:1764: for (int i = 0; i < 10; i++) {
SCOPED_TRACE please with the iteration number.

[gavinp, 2010-08-19 18:17:22]

LGTM.

http://codereview.chromium.org/3167020/diff/25001/26001
File net/disk_cache/backend_impl.cc (right):

http://codereview.chromium.org/3167020/diff/25001/26001#newcode1893
net/disk_cache/backend_impl.cc:1893: total_memory = total_memory * 2 / 100;
How did you arrive at 2%?

http://codereview.chromium.org/3167020/diff/25001/26003
File net/disk_cache/backend_unittest.cc (right):

http://codereview.chromium.org/3167020/diff/25001/26003#newcode1810
net/disk_cache/backend_unittest.cc:1810: }
NIT: add a newline here

http://codereview.chromium.org/3167020/diff/25001/26004
File net/disk_cache/disk_cache_test_base.cc (right):

http://codereview.chromium.org/3167020/diff/25001/26004#newcode225
net/disk_cache/disk_cache_test_base.cc:225: }
nit: add a newline

[rvargas (doing something else), 2010-08-20 18:22:21]

Thanks.

The newlines are there, it's just rietveld / lint.

http://codereview.chromium.org/3167020/diff/25001/26001
File net/disk_cache/backend_impl.cc (right):

http://codereview.chromium.org/3167020/diff/25001/26001#newcode1893
net/disk_cache/backend_impl.cc:1893: total_memory = total_memory * 2 / 100;
On 2010/08/19 18:17:22, gavinp wrote:
> How did you arrive at 2%?

From nowhere?. That seems like a reasonable number, but there is no real reason.
That's the same number used for the incognito cache, but with a lower limit.