From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753047AbcKUE7x (ORCPT ); Sun, 20 Nov 2016 23:59:53 -0500 Received: from mail-pg0-f65.google.com ([74.125.83.65]:34437 "EHLO mail-pg0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751950AbcKUE7w (ORCPT ); Sun, 20 Nov 2016 23:59:52 -0500 Message-ID: <1479704390.8455.398.camel@edumazet-glaptop3.roam.corp.google.com> Subject: Re: Linux 4.9-rc6 From: Eric Dumazet To: Al Viro Cc: Linus Torvalds , Linux Kernel Mailing List Date: Sun, 20 Nov 2016 20:59:50 -0800 In-Reply-To: <20161121013558.GG1555@ZenIV.linux.org.uk> References: <1479680873.8455.386.camel@edumazet-glaptop3.roam.corp.google.com> <20161121013558.GG1555@ZenIV.linux.org.uk> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.10.4-0ubuntu2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2016-11-21 at 01:35 +0000, Al Viro wrote: > > Umm... One possibility would be something like fs/namespace.c:m_start() - > if nothing has changed since the last time, just use a cached pointer. > That has sped the damn thing (/proc/mounts et.al.) big way, but it's > dependent upon having an event count updated whenever we change the > mount tree - doing the same for vma_area list might or might not be > a good idea. /proc/mounts and friends get ->poll() on that as well; > that probably would _not_ be a good idea in this case. Yes, a generation number could help in some cases. Another potential issue with CONFIG_VMAP_STACK is that we make no attempt to allocate 4 consecutive pages. Even if we have plenty of memory, 4 calls to alloc_page() are likely to give us 4 pages in completely different locations. Here I printed the hugepage number of the 4 pages for some stacks : 0xffffc9001a07c000-0xffffc9001a081000 20480 _do_fork+0xe1/0x360 pages=4 vmalloc Hfcac Hfeba Hfec0 Hfc9d N0=4 0xffffc9001a084000-0xffffc9001a089000 20480 _do_fork+0xe1/0x360 pages=4 vmalloc Hfc79 Hfc79 Hfc79 Hfc83 N0=4 0xffffc9001a08c000-0xffffc9001a091000 20480 _do_fork+0xe1/0x360 pages=4 vmalloc Hfc9b Hfe91 Hfebe Hfca2 N0=4 0xffffc9001a094000-0xffffc9001a099000 20480 _do_fork+0xe1/0x360 pages=4 vmalloc Hfcaa Hfcaa Hfca6 Hfebc N0=4 0xffffc9001a09c000-0xffffc9001a0a1000 20480 _do_fork+0xe1/0x360 pages=4 vmalloc Hfe9b Hfe90 Hff09 Hfefb N0=4 0xffffc9001a0a4000-0xffffc9001a0a9000 20480 _do_fork+0xe1/0x360 pages=4 vmalloc Hfe94 Hfe62 Hfea0 Hfe7b N0=4 0xffffc9001a0ac000-0xffffc9001a0b1000 20480 _do_fork+0xe1/0x360 pages=4 vmalloc Hfe78 Hff05 Hff05 Hfc74 N0=4 0xffffc9001a0b4000-0xffffc9001a0b9000 20480 _do_fork+0xe1/0x360 pages=4 vmalloc Hfc9b Hfc9b Hfe83 Hf782 N0=4 0xffffc9001a0bc000-0xffffc9001a0c1000 20480 _do_fork+0xe1/0x360 pages=4 vmalloc Hfe78 Hfe78 Hfc7f Hfc7f N0=4 0xffffc9001a0c4000-0xffffc9001a0c9000 20480 _do_fork+0xe1/0x360 pages=4 vmalloc Hfebe Hfebe Hfe82 Hfe85 N0=4 0xffffc9001a0cc000-0xffffc9001a0d1000 20480 _do_fork+0xe1/0x360 pages=4 vmalloc Hfc6b Hfe62 Hfe62 Hfcaa N0=4 0xffffc9001a0d4000-0xffffc9001a0d9000 20480 _do_fork+0xe1/0x360 pages=4 vmalloc Hfebd Hfebd Hfc92 Hfc92 N0=4 This is a vmalloc() generic issue that is worth fixing now ? Note this RFC might conflict with NUMA interleave policy. diff --git a/mm/vmalloc.c b/mm/vmalloc.c index f2481cb4e6b2..0123e97debb9 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -1602,9 +1602,10 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask, pgprot_t prot, int node) { struct page **pages; - unsigned int nr_pages, array_size, i; + unsigned int nr_pages, array_size, i, j; const gfp_t nested_gfp = (gfp_mask & GFP_RECLAIM_MASK) | __GFP_ZERO; const gfp_t alloc_mask = gfp_mask | __GFP_NOWARN; + const gfp_t multi_alloc_mask = (gfp_mask & ~__GFP_DIRECT_RECLAIM) | __GFP_NORETRY; nr_pages = get_vm_area_size(area) >> PAGE_SHIFT; array_size = (nr_pages * sizeof(struct page *)); @@ -1624,20 +1625,34 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask, return NULL; } - for (i = 0; i < area->nr_pages; i++) { - struct page *page; - - if (node == NUMA_NO_NODE) - page = alloc_page(alloc_mask); - else - page = alloc_pages_node(node, alloc_mask, 0); + for (i = 0; i < area->nr_pages;) { + struct page *page = NULL; + unsigned int chunk_order = min(ilog2(area->nr_pages - i), MAX_ORDER - 1); + + while (chunk_order && !page) { + if (node == NUMA_NO_NODE) + page = alloc_pages(multi_alloc_mask, chunk_order); + else + page = alloc_pages_node(node, multi_alloc_mask, chunk_order); + if (page) + split_page(page, chunk_order); + else + chunk_order--; + } + if (!page) { + if (node == NUMA_NO_NODE) + page = alloc_pages(alloc_mask, 0); + else + page = alloc_pages_node(node, alloc_mask, 0); + } if (unlikely(!page)) { /* Successfully allocated i pages, free them in __vunmap() */ area->nr_pages = i; goto fail; } - area->pages[i] = page; + for (j = 0; j < (1 << chunk_order); j++) + area->pages[i++] = page++; if (gfpflags_allow_blocking(gfp_mask)) cond_resched(); }