Re: [RFC v2 PATCH 4/4] mm: pre zero out free pages to speed up page allocation for __GFP_ZERO
From: Dave Hansen <hidden>
Date: 2021-01-04 19:52:37
Also in:
linux-mm, lkml
On 1/4/21 11:27 AM, Matthew Wilcox wrote:
On Mon, Jan 04, 2021 at 11:19:13AM -0800, Dave Hansen wrote:quoted
On 12/21/20 8:30 AM, Liang Li wrote:quoted
--- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h@@ -137,6 +137,9 @@ enum pageflags { #endif #ifdef CONFIG_64BIT PG_arch_2, +#endif +#ifdef CONFIG_PREZERO_PAGE + PG_zero, #endif __NR_PAGEFLAGS,I don't think this is worth a generic page->flags bit. There's a ton of space in 'struct page' for pages that are in the allocator. Can't we use some of that space?I was going to object to that too, but I think the entire approach is flawed and needs to be thrown out. It just nukes the caches in extremely subtle and hard to measure ways, lowering overall system performance.
Yeah, it certainly can't be the default, but it *is* useful for thing where we know that there are no cache benefits to zeroing close to where the memory is allocated. The trick is opting into it somehow, either in a process or a VMA. _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization