On Fri, Sep 18, 2020 at 10:20:46AM +0200, Rasmus Villemoes wrote: > On 04/06/2020 12.31, Stefan Roese wrote: > > On 04.06.20 11:30, Rasmus Villemoes wrote: > >> Calling WATCHDOG_RESET for each and every cache line is overkill. > >> > >> In our case, the kernel image is a little over 7MB, and the almost > >> 500000 calls of WATCHDOG_RESET() adds about one second to the > >> boottime. > >> > >> I very highly doubt there's any real hardware where flushing 64K > >> from cache to memory takes more than a few milliseconds, so this > >> should be completely safe. Since it reduces the number of > >> WATCHDOG_RESET() calls by roughly a factor of 1000, the overhead from > >> those is practically eliminated. (Just in case the range flushed is so > >> small that it doesn't cross a 64K boundary, add a single > >> WATCHDOG_RESET() between the loops). > >> > >> 64K is chosen because that's also the default chunk size used by the > >> hashing algorithms, and when, say, a sha256 digest of a kernel image of > >> a few MB is being verified, that's almost guaranteed to be cache-cold, > >> so apart from the computations being done, the hashing is also bounded > >> by memory speed - so if 64K works for those cases, it should certainly > >> also work when memory access is the only thing being done. > >> > >> Signed-off-by: Rasmus Villemoes <rasmus.villem...@prevas.dk> > > > > Reviewed-by: Stefan Roese <s...@denx.de> > > Ping.
This too should end up in -next "soon". Thanks. -- Tom
signature.asc
Description: PGP signature
