+ Renesas people Hello Will, hello Ard, On Fri, Sep 07, 2018 at 03:44:47PM +0100, Will Deacon wrote: > On Thu, Sep 06, 2018 at 01:24:22PM +0200, Ard Biesheuvel wrote: > > OK so we can summarize the benefits of this series as follows: > > - boot time on a virtual model of a Samurai CPU drops from 109 to 62 seconds > > - boot time on a QDF2400 arm64 server with 96 GB of RAM drops by ~15 > > *milliseconds* > > > > Google was not very helpful in figuring out what a Samurai CPU is and > > why we should care about the boot time of Linux running on a virtual > > model of it, and the 15 ms speedup is not that compelling either. > > > > Apologies to Jia that it took 11 revisions to reach this conclusion, > > but in /my/ opinion, tweaking the fragile memblock/pfn handling code > > for this reason is totally unjustified, and we're better off > > disregarding these patches. > > Oh, we're talking about a *simulator* for the significant boot time > improvement here? I didn't realise that, so I agree that the premise of > this patch set looks pretty questionable given how much "fun" we've had > with the memmap on arm and arm64. > > Will Similar to https://lkml.org/lkml/2018/1/24/420, my measurements show that the boot time of R-Car H3-ES2.0 Salvator-X (having 4GiB RAM) is decreased by ~135-140ms with this patch-set applied on top of v4.19-rc3. I agree that in the Desktop realm you would barely perceive the 140ms difference, but saving 140ms on the automotive SoC (designed for products which must comply with 2s-to-rear-view-camera NHTSA US regulations) *is* significant. FWIW, cppcheck and `checkpatch --strict` report style issues for patches #2 and #3. I hope these can be fixed and the review process can go on? From functional standpoint, I did some dynamic testing on H3-Salvator-X with UBSAN/KASAN=y and didn't observe any regressions, so: Tested-by: Eugeniu Rosca <erosca@xxxxxxxxxxxxxx> Best regards, Eugeniu.
