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 hF7niVvK 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2/24/26 11:26, Linus Walleij wrote: >> >>>> After the introduction of clear_pages() we exploit the >>>> fact that the process vm_area is allocated in contiguous >>>> pages to just clear them all in one swift operation. >>> >>> The pages are virtually contiguous (vmalloc IIUC), not necessarily >>> physically contiguous. For clear_pages() that should work. >> >> Yeah that's what I meant with contiguous, sorry. >> >>>> /* Clear stale pointers from reused stack. */ >>>> - memset(stack, 0, THREAD_SIZE); >>>> + clear_pages(vm_area->addr, vm_area->nr_pages); >>> >>> LGTM. >>> >>> Do we have any idea about performance impact etc? >> >> I have a pending patch for implementing clear_pages() for arm64, >> https://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-integrator.= git/log/?h=3Db4/aarch64-clear-pages >> which is in a performance test loop, once I get baseline data from that >> I can test something fork-intensive (hackbench, I guess) with this patch= on top. >> >> So making that patch made me remember this one code site... > > I'll note that clear_pages() documents: "When running under preemptible > models this is not a problem. Under cooperatively scheduled models, > however, the caller is expected to limit @npages to no more than > PROCESS_PAGES_NON_PREEMPT_BATCH." > > We discussed during review that we should probably move that batching > logic into clear_pages() at some point. Yeah. However, clear_pages() can be architecturally overriden. I don't see any use for a non-batched implementation. So, maybe the arch version should become __clear_pages() and clear_pages() can always do the appropriate batching. -- ankur