On Wed 10-05-17 11:19:43, David S. Miller wrote: > From: Michal Hocko <mhocko@xxxxxxxxxx> > Date: Wed, 10 May 2017 16:57:26 +0200 > > > Have you measured that? I do not think it would be super hard to > > measure. I would be quite surprised if this added much if anything at > > all as the whole struct page should be in the cache line already. We do > > set reference count and other struct members. Almost nobody should be > > looking at our page at this time and stealing the cache line. On the > > other hand a large memcpy will basically wipe everything away from the > > cpu cache. Or am I missing something? > > I guess it might be clearer if you understand what the block > initializing stores do on sparc64. There are no memory accesses at > all. > > The cpu just zeros out the cache line, that's it. > > No L3 cache line is allocated. So this "wipe everything" behavior > will not happen in the L3. OK, good to know. My undestanding of sparc64 is close to zero. Anyway, do you agree that doing the struct page initialization along with other writes to it shouldn't add a measurable overhead comparing to pre-zeroing of larger block of struct pages? We already have an exclusive cache line and doing one 64B write along with few other stores should be basically the same. -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
