Bug 21451 – tune cMaxInactiveFontData when cleaning old FontData

• Component: Platform
• Status: RESOLVED WONTFIX

[Mike Belshe]

When Chromium picked up the latest WebKit; we discovered that our international page cycler test took a ~20% performance hit.  This was due to the FontData cleanup.  The test is a bit brutal, as it intentionally uses more fonts than users are likely to use.

It turns out that tuning cMaxInactiveFontData (FontCache.cpp) from a constant 120 to a constant 256 works around the problem with this test.

I'm hoping that this value is currently somewhat arbitrary, so that nobody objects to this change.  However, I could submit a patch to allow platform-specific tuning of this value if that is preferred.

How much more memory does that amount to? What about other scarce resources used by the cache (GDI handles perhaps)?

[Dave Hyatt]

I'm fine with raising the constant if Dan is.

[Maciej Stachowiak]

I think an international test of this sort would almost certainly use more fonts than any normal user would, since most people do not browse to pages using many different scripts. I do not think it would be a good tradeoff to use more memory for solely for the benefit of such a benchmark, if we do not think it would help any real browsing scenario.

However, it would help to have data on the increase in memory use from changing this constant.

[Maciej Stachowiak]

Another useful piece of data would be to determine how many different fonts are loaded in the course of typical browsing for various users.

[Dimitri Glazkov (Google)]

I think we'll roll our fork out and see what difference it makes.

[Dimitri Glazkov (Google)]

Obsoleting old bugs.