Yeah, if we're not testing them I guess we don't have to make or distribute them at all.
-David On Wednesday, October 10, 2012 2:58:18 PM UTC-7, Justin Lebar wrote: > By "turning off Linux PGO testing", you really mean "stop making and > > distributing Linux PGO builds," right? > > > > The main reason I'd want Linux PGO is for mobile. On desktop Linux, > > most users (I expect) don't run our builds, so it's not a big deal if > > they're some percent slower. (Unless distros commonly do PGO builds > > of Firefox?) But we're not doing mobile Linux PGO builds (that I know > > of), and I don't expect success with desktop PGO is much related to > > success with mobile PGO. > > > > -Justin > > > > On Wed, Oct 10, 2012 at 5:14 PM, David Anderson wrote: > > > Hi, > > > > > > After being faced with the prospect of debugging Yet Another PGO-only Bug, > > I propose that we stop testing Linux PGO builds. One of these bugs is > > causing perma-red on Aurora (bug 799295). The developer cost of figuring > > out how to reproduce, debug, and fix these problems is quite high, and even > > higher where a specific distro and compiler version might be in play. The > > cost is not worth the benefit of testing this configuration. > > > > > > All evidence at Mozilla suggests that PGO is endlessly buggy, and I've > > heard this has been true historically in compilers. PGO deeply and > > zealously modifies calling conventions, function bodies, and large > > callgraphs, causing subtle problems, often topcrashes, that are difficult > > to reproduce and nearly impossible to debug. The result is that we litter > > the codebase with untestable deoptimization hints that may or may not > > randomly become obsolete. > > > > > > This is depressing on any platform, but at least on Windows, we have a > > single compiler version to worry about (and, notably, a compiler that has > > PGO bugs even with a huge amount of resources behind its development). It > > is possible that PGO could expose real bugs. If so, we'll see the bug one > > way or another, likely in a context that is more easily reproducible and > > easier to debug. > > > > > > So, let's turn off Linux PGO testing, free up releng resources, and save > > ourselves the inevitable pain and suffering. > > > > > > -David > > > _______________________________________________ > > > dev-platform mailing list > > > dev-platform@lists.mozilla.org > > > https://lists.mozilla.org/listinfo/dev-platform _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
