On Tue, Sep 04, 2012 at 01:59:29PM +0300, Aryeh Gregor wrote: > On Tue, Sep 4, 2012 at 3:19 AM, Gregory Szorc <g...@mozilla.com> wrote: > > I re-ran some builds on my desktop with my instrumented build system that > > records system metrics and an SSD clobber build was only ~50s faster than > > the same build on a 7200RPM drive. This comes out to ~5%, which isn't much. > > Both results were on a freshly booted virtual machine (read: empty page > > cache) that had access to 12GB of memory. This was also with ccache disabled > > (all my previous measurements on list posts and my personal blog were with > > ccache enabled, which definitely has an impact on I/O). > > Having no page cache and no ccache is great for getting stable > numbers, but not very realistic. In practice, most compiles will have > the page cache populated, so it probably won't even be 5%. > > (On the other hand, in principle ccache should increase the amount of > on-disk data being accessed, and therefore *increase* the value of an > SSD. But I haven't noticed this in practice.)
On the other hand, the ccache miss rate is pretty high, at least it is for me, so in the end, ccache might not be a win at all. Mike _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
