Increase GPU transfer buffer alignment to 16 bytes.

Increase GPU transfer buffer alignment to 16 bytes.

This might help improve the performance of copies from the buffer, particularly inside UpdateSubresource in the GPU driver.

BUG=524305
Committed: https://crrev.com/bbd6ee83dd7fea70ece8d5c73317390ef8d9478b
Cr-Commit-Position: refs/heads/master@{#372250}

[jbauman, 2016-01-27 22:17:59]

jbauman@chromium.org changed reviewers:
+ kbr@chromium.org

[Ken Russell (switch to Gerrit), 2016-01-28 01:04:54]

kbr@chromium.org changed reviewers:
+ piman@chromium.org, vmiura@chromium.org, zmo@chromium.org

[Ken Russell (switch to Gerrit), 2016-01-28 01:04:54]

I'm actually not an OWNER.

What's the likely overhead? Minimal, I suppose, given that most allocations out
of the transfer buffer are large?

[jbauman, 2016-01-28 01:14:13]

On 2016/01/28 01:04:54, Ken Russell wrote:
> I'm actually not an OWNER.
> 
> What's the likely overhead? Minimal, I suppose, given that most allocations
out
> of the transfer buffer are large?

Likely pretty small. We'll see on the bots, but I suspect the alignment costs
are also dwarfed by the default size of the transfer buffer.

[vmiura, 2016-01-28 01:47:43]

Looks reasonable.  Does it improve performance just by changing it?

[jbauman, 2016-01-28 02:27:04]

On 2016/01/28 01:47:43, vmiura wrote:
> Looks reasonable.  Does it improve performance just by changing it?

No, doesn't seem to improve performance by itself. The main reason I want this
is to re-land https://chromium-review.googlesource.com/293742, which was
reverted due to https://code.google.com/p/chromium/issues/detail?id=532647 . I'm
not sure why performance got so much worse due to that patch on NVIDIA drivers,
but one possible reason is that the alignment of the source buffer given to the
driver is insufficient. This patch should help determine that.

[piman, 2016-01-29 00:43:34]

LGTM. I thought we had 16 already actually, for similar reasons, but that's only
on the MappedMemoryManager/FencedAllocator. Doing it for the TransferBuffer as
well seems perfectly reasonable.

[jbauman, 2016-01-29 00:46:10]

The CQ bit was checked by jbauman@chromium.org

[commit-bot: I haz the power, 2016-01-29 00:46:23]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1635183003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1635183003/1

[commit-bot: I haz the power, 2016-01-29 01:54:45]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-01-29 01:55:38]

Description was changed from

==========
Increase GPU transfer buffer alignment to 16 bytes.

This might help improve the performance of copies from the buffer, particularly
inside UpdateSubresource in the GPU driver.

BUG=524305
==========

to

==========
Increase GPU transfer buffer alignment to 16 bytes.

This might help improve the performance of copies from the buffer, particularly
inside UpdateSubresource in the GPU driver.

BUG=524305

Committed: https://crrev.com/bbd6ee83dd7fea70ece8d5c73317390ef8d9478b
Cr-Commit-Position: refs/heads/master@{#372250}
==========

[commit-bot: I haz the power, 2016-01-29 01:55:39]

Patchset 1 (id:??) landed as
https://crrev.com/bbd6ee83dd7fea70ece8d5c73317390ef8d9478b
Cr-Commit-Position: refs/heads/master@{#372250}