From patchwork Mon Jul 29 11:19:21 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Colin Ian King X-Patchwork-Id: 1138319 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=lists.ubuntu.com (client-ip=91.189.94.19; helo=huckleberry.canonical.com; envelope-from=kernel-team-bounces@lists.ubuntu.com; receiver=) Authentication-Results: ozlabs.org; dmarc=fail (p=none dis=none) header.from=canonical.com Received: from huckleberry.canonical.com (huckleberry.canonical.com [91.189.94.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 45xxzV5h5Rz9sMQ; Mon, 29 Jul 2019 21:19:34 +1000 (AEST) Received: from localhost ([127.0.0.1] helo=huckleberry.canonical.com) by huckleberry.canonical.com with esmtp (Exim 4.86_2) (envelope-from ) id 1hs3gh-0001wa-1v; Mon, 29 Jul 2019 11:19:31 +0000 Received: from youngberry.canonical.com ([91.189.89.112]) by huckleberry.canonical.com with esmtps (TLS1.0:DHE_RSA_AES_128_CBC_SHA1:128) (Exim 4.86_2) (envelope-from ) id 1hs3ga-0001tQ-D1 for kernel-team@lists.ubuntu.com; Mon, 29 Jul 2019 11:19:24 +0000 Received: from 1.general.cking.uk.vpn ([10.172.193.212] helo=localhost) by youngberry.canonical.com with esmtpsa (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.76) (envelope-from ) id 1hs3gZ-0000VF-WC; Mon, 29 Jul 2019 11:19:24 +0000 From: Colin King To: kernel-team@lists.ubuntu.com Subject: [PATCH 3/4][SRU][B-HWE][D][V3] mm/vmalloc.c: add priority threshold to __purge_vmap_area_lazy() Date: Mon, 29 Jul 2019 12:19:21 +0100 Message-Id: <20190729111922.8611-4-colin.king@canonical.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190729111922.8611-1-colin.king@canonical.com> References: <20190729111922.8611-1-colin.king@canonical.com> MIME-Version: 1.0 X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.20 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kernel-team-bounces@lists.ubuntu.com Sender: "kernel-team" From: "Uladzislau Rezki (Sony)" BugLink: https://bugs.launchpad.net/bugs/1838115 Commit 763b218ddfaf ("mm: add preempt points into __purge_vmap_area_lazy()") introduced some preempt points, one of those is making an allocation more prioritized over lazy free of vmap areas. Prioritizing an allocation over freeing does not work well all the time, i.e. it should be rather a compromise. 1) Number of lazy pages directly influences the busy list length thus on operations like: allocation, lookup, unmap, remove, etc. 2) Under heavy stress of vmalloc subsystem I run into a situation when memory usage gets increased hitting out_of_memory -> panic state due to completely blocking of logic that frees vmap areas in the __purge_vmap_area_lazy() function. Establish a threshold passing which the freeing is prioritized back over allocation creating a balance between each other. Using vmalloc test driver in "stress mode", i.e. When all available test cases are run simultaneously on all online CPUs applying a pressure on the vmalloc subsystem, my HiKey 960 board runs out of memory due to the fact that __purge_vmap_area_lazy() logic simply is not able to free pages in time. How I run it: 1) You should build your kernel with CONFIG_TEST_VMALLOC=m 2) ./tools/testing/selftests/vm/test_vmalloc.sh stress During this test "vmap_lazy_nr" pages will go far beyond acceptable lazy_max_pages() threshold, that will lead to enormous busy list size and other problems including allocation time and so on. Link: http://lkml.kernel.org/r/20190124115648.9433-3-urezki@gmail.com Signed-off-by: Uladzislau Rezki (Sony) Reviewed-by: Andrew Morton Cc: Michal Hocko Cc: Matthew Wilcox Cc: Thomas Garnier Cc: Oleksiy Avramchenko Cc: Steven Rostedt Cc: Joel Fernandes Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Tejun Heo Cc: Joel Fernandes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds (cherry picked from commit 68571be99f323c3c3db62a8513a43380ccefe97c) Signed-off-by: Colin Ian King --- mm/vmalloc.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 1bf8fa9..07c9a18 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -661,23 +661,27 @@ static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end) struct llist_node *valist; struct vmap_area *va; struct vmap_area *n_va; - bool do_free = false; + int resched_threshold; lockdep_assert_held(&vmap_purge_lock); valist = llist_del_all(&vmap_purge_list); + if (unlikely(valist == NULL)) + return false; + + /* + * TODO: to calculate a flush range without looping. + * The list can be up to lazy_max_pages() elements. + */ llist_for_each_entry(va, valist, purge_list) { if (va->va_start < start) start = va->va_start; if (va->va_end > end) end = va->va_end; - do_free = true; } - if (!do_free) - return false; - flush_tlb_kernel_range(start, end); + resched_threshold = (int) lazy_max_pages() << 1; spin_lock(&vmap_area_lock); llist_for_each_entry_safe(va, n_va, valist, purge_list) { @@ -685,7 +689,9 @@ static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end) __free_vmap_area(va); atomic_sub(nr, &vmap_lazy_nr); - cond_resched_lock(&vmap_area_lock); + + if (atomic_read(&vmap_lazy_nr) < resched_threshold) + cond_resched_lock(&vmap_area_lock); } spin_unlock(&vmap_area_lock); return true;