From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [PATCH 2/2] lib/librte_eal: Remove unnecessary hugepage zero-filling Date: Sun, 22 Nov 2015 18:28:00 -0800 Message-ID: <20151122182800.397e0701@xeon-e3> References: <1448219615-63746-1-git-send-email-zhihong.wang@intel.com> <1448219615-63746-3-git-send-email-zhihong.wang@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: dev@dpdk.org To: Zhihong Wang Return-path: Received: from mail-pa0-f48.google.com (mail-pa0-f48.google.com [209.85.220.48]) by dpdk.org (Postfix) with ESMTP id 43B7A8E6C for ; Mon, 23 Nov 2015 03:27:49 +0100 (CET) Received: by pacdm15 with SMTP id dm15so175862747pac.3 for ; Sun, 22 Nov 2015 18:27:48 -0800 (PST) In-Reply-To: <1448219615-63746-3-git-send-email-zhihong.wang@intel.com> List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On Sun, 22 Nov 2015 14:13:35 -0500 Zhihong Wang wrote: > The kernel fills new allocated (huge) pages with zeros. > DPDK just has to populate page tables to trigger the allocation. > > Signed-off-by: Zhihong Wang > --- > lib/librte_eal/linuxapp/eal/eal_memory.c | 20 ++++++-------------- > 1 file changed, 6 insertions(+), 14 deletions(-) > > diff --git a/lib/librte_eal/linuxapp/eal/eal_memory.c b/lib/librte_eal/linuxapp/eal/eal_memory.c > index 0de75cd..21a5146 100644 > --- a/lib/librte_eal/linuxapp/eal/eal_memory.c > +++ b/lib/librte_eal/linuxapp/eal/eal_memory.c > @@ -399,8 +399,10 @@ map_all_hugepages(struct hugepage_file *hugepg_tbl, > return -1; > } > > + /* map the segment, and populate page tables, > + * the kernel fills this segment with zeros */ > virtaddr = mmap(vma_addr, hugepage_sz, PROT_READ | PROT_WRITE, > - MAP_SHARED, fd, 0); > + MAP_SHARED | MAP_POPULATE, fd, 0); > if (virtaddr == MAP_FAILED) { > RTE_LOG(ERR, EAL, "%s(): mmap failed: %s\n", __func__, > strerror(errno)); > @@ -410,7 +412,6 @@ map_all_hugepages(struct hugepage_file *hugepg_tbl, > > if (orig) { > hugepg_tbl[i].orig_va = virtaddr; > - memset(virtaddr, 0, hugepage_sz); > } > else { > hugepg_tbl[i].final_va = virtaddr; > @@ -529,22 +530,16 @@ remap_all_hugepages(struct hugepage_file *hugepg_tbl, struct hugepage_info *hpi) > > old_addr = vma_addr; > > - /* map new, bigger segment */ > + /* map new, bigger segment, and populate page tables, > + * the kernel fills this segment with zeros */ > vma_addr = mmap(vma_addr, total_size, > - PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); > + PROT_READ | PROT_WRITE, MAP_SHARED | MAP_POPULATE, fd, 0); > > if (vma_addr == MAP_FAILED || vma_addr != old_addr) { > RTE_LOG(ERR, EAL, "%s(): mmap failed: %s\n", __func__, strerror(errno)); > close(fd); > return -1; > } > - > - /* touch the page. this is needed because kernel postpones mapping > - * creation until the first page fault. with this, we pin down > - * the page and it is marked as used and gets into process' pagemap. > - */ > - for (offset = 0; offset < total_size; offset += hugepage_sz) > - *((volatile uint8_t*) RTE_PTR_ADD(vma_addr, offset)); > } > > /* set shared flock on the file. */ > @@ -592,9 +587,6 @@ remap_all_hugepages(struct hugepage_file *hugepg_tbl, struct hugepage_info *hpi) > } > } > > - /* zero out the whole segment */ > - memset(hugepg_tbl[page_idx].final_va, 0, total_size); > - > page_idx++; > } > Nice, especially on slow machines or with large memory. Acked-by: Stephen Hemminger