From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from shards.monkeyblade.net (shards.monkeyblade.net [184.105.139.130]) by lists.ozlabs.org (Postfix) with ESMTP id 3vq2wk35j7zDq7c for ; Fri, 24 Mar 2017 10:35:31 +1100 (AEDT) Date: Thu, 23 Mar 2017 16:35:20 -0700 (PDT) Message-Id: <20170323.163520.123614131649571916.davem@davemloft.net> To: willy@infradead.org Cc: pasha.tatashin@oracle.com, linux-kernel@vger.kernel.org, sparclinux@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.or Subject: Re: [v1 0/5] parallelized "struct page" zeroing From: David Miller In-Reply-To: <20170323232638.GB29134@bombadil.infradead.org> References: <1490310113-824438-1-git-send-email-pasha.tatashin@oracle.com> <20170323232638.GB29134@bombadil.infradead.org> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: Matthew Wilcox Date: Thu, 23 Mar 2017 16:26:38 -0700 > On Thu, Mar 23, 2017 at 07:01:48PM -0400, Pavel Tatashin wrote: >> When deferred struct page initialization feature is enabled, we get a >> performance gain of initializing vmemmap in parallel after other CPUs are >> started. However, we still zero the memory for vmemmap using one boot CPU. >> This patch-set fixes the memset-zeroing limitation by deferring it as well. >> >> Here is example performance gain on SPARC with 32T: >> base >> https://hastebin.com/ozanelatat.go >> >> fix >> https://hastebin.com/utonawukof.go >> >> As you can see without the fix it takes: 97.89s to boot >> With the fix it takes: 46.91 to boot. > > How long does it take if we just don't zero this memory at all? We seem > to be initialising most of struct page in __init_single_page(), so it > seems like a lot of additional complexity to conditionally zero the rest > of struct page. Alternatively, just zero out the entire vmemmap area when it is setup in the kernel page tables.