On Thu, 12 Apr 2012, Tommi Virtanen wrote: > On Thu, Apr 12, 2012 at 12:45, Sage Weil <sage@xxxxxxxxxxxx> wrote: > >> So maybe we could reduce the memory footprint of the cache, but keep it's > >> performance. > > > > I'm not familiar with the performance implications of KSM, but the > > objectcacher doesn't modify existing buffers in place, so I suspect it's a > > good candidate. And it looks like there's minimal effort in enabling > > it... > > Are the objectcacher cache entries full pages, page aligned, with no > bookkeeping data inside the page? Those are pretty much the > requirements for page-granularity dedup to work.. Some buffers are, some aren't, but we'd only want to madvise on page aligned ones. The messenger is careful to read things into aligned memory, and librbd will only be getting block-sized (probably page-sized, if we say we have 4k blocks) IO... so that should include every buffer in this case. sage
