From owner-svn-src-all@freebsd.org Tue Jun 21 17:49:34 2016 Return-Path: Delivered-To: svn-src-all@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id BA324AC5646; Tue, 21 Jun 2016 17:49:34 +0000 (UTC) (envelope-from kib@FreeBSD.org) Received: from repo.freebsd.org (repo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 6D45E1721; Tue, 21 Jun 2016 17:49:34 +0000 (UTC) (envelope-from kib@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id u5LHnX50078954; Tue, 21 Jun 2016 17:49:33 GMT (envelope-from kib@FreeBSD.org) Received: (from kib@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id u5LHnXLk078952; Tue, 21 Jun 2016 17:49:33 GMT (envelope-from kib@FreeBSD.org) Message-Id: <201606211749.u5LHnXLk078952@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: kib set sender to kib@FreeBSD.org using -f From: Konstantin Belousov Date: Tue, 21 Jun 2016 17:49:33 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r302063 - head/sys/vm X-SVN-Group: head MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 21 Jun 2016 17:49:34 -0000 Author: kib Date: Tue Jun 21 17:49:33 2016 New Revision: 302063 URL: https://svnweb.freebsd.org/changeset/base/302063 Log: The vmtotal sysctl handler marks active vm objects to calculate statistics. Marking is done by setting the OBJ_ACTIVE flag. The flags change is locked, but the problem is that many parts of system assume that vm object initialization ensures that no other code could change the object, and thus performed lockless. The end result is corrupted flags in vm objects, most visible is spurious OBJ_DEAD flag, causing random hangs. Avoid the active object marking, instead provide equally inexact but immutable is_object_alive() definition for the object mapped state. Avoid iterating over the processes mappings altogether by using arguably improved definition of the paging thread as one which sleeps on the v_free_count. PR: 204764 Diagnosed by: pho Tested by: pho (previous version) Reviewed by: alc Sponsored by: The FreeBSD Foundation MFC after: 1 week Approved by: re (gjb) Modified: head/sys/vm/vm_meter.c head/sys/vm/vm_object.h Modified: head/sys/vm/vm_meter.c ============================================================================== --- head/sys/vm/vm_meter.c Tue Jun 21 15:49:09 2016 (r302062) +++ head/sys/vm/vm_meter.c Tue Jun 21 17:49:33 2016 (r302063) @@ -89,29 +89,31 @@ SYSCTL_PROC(_vm, VM_LOADAVG, loadavg, CT CTLFLAG_MPSAFE, NULL, 0, sysctl_vm_loadavg, "S,loadavg", "Machine loadaverage history"); +/* + * This function aims to determine if the object is mapped, + * specifically, if it is referenced by a vm_map_entry. Because + * objects occasionally acquire transient references that do not + * represent a mapping, the method used here is inexact. However, it + * has very low overhead and is good enough for the advisory + * vm.vmtotal sysctl. + */ +static bool +is_object_active(vm_object_t obj) +{ + + return (obj->ref_count > obj->shadow_count); +} + static int vmtotal(SYSCTL_HANDLER_ARGS) { - struct proc *p; struct vmtotal total; - vm_map_entry_t entry; vm_object_t object; - vm_map_t map; - int paging; + struct proc *p; struct thread *td; - struct vmspace *vm; bzero(&total, sizeof(total)); - /* - * Mark all objects as inactive. - */ - mtx_lock(&vm_object_list_mtx); - TAILQ_FOREACH(object, &vm_object_list, object_list) { - VM_OBJECT_WLOCK(object); - vm_object_clear_flag(object, OBJ_ACTIVE); - VM_OBJECT_WUNLOCK(object); - } - mtx_unlock(&vm_object_list_mtx); + /* * Calculate process statistics. */ @@ -132,11 +134,15 @@ vmtotal(SYSCTL_HANDLER_ARGS) case TDS_INHIBITED: if (TD_IS_SWAPPED(td)) total.t_sw++; - else if (TD_IS_SLEEPING(td) && - td->td_priority <= PZERO) - total.t_dw++; - else - total.t_sl++; + else if (TD_IS_SLEEPING(td)) { + if (td->td_priority <= PZERO) + total.t_dw++; + else + total.t_sl++; + if (td->td_wchan == + &vm_cnt.v_free_count) + total.t_pw++; + } break; case TDS_CAN_RUN: @@ -154,29 +160,6 @@ vmtotal(SYSCTL_HANDLER_ARGS) } } PROC_UNLOCK(p); - /* - * Note active objects. - */ - paging = 0; - vm = vmspace_acquire_ref(p); - if (vm == NULL) - continue; - map = &vm->vm_map; - vm_map_lock_read(map); - for (entry = map->header.next; - entry != &map->header; entry = entry->next) { - if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) || - (object = entry->object.vm_object) == NULL) - continue; - VM_OBJECT_WLOCK(object); - vm_object_set_flag(object, OBJ_ACTIVE); - paging |= object->paging_in_progress; - VM_OBJECT_WUNLOCK(object); - } - vm_map_unlock_read(map); - vmspace_free(vm); - if (paging) - total.t_pw++; } sx_sunlock(&allproc_lock); /* @@ -202,9 +185,18 @@ vmtotal(SYSCTL_HANDLER_ARGS) */ continue; } + if (object->ref_count == 1 && + (object->flags & OBJ_NOSPLIT) != 0) { + /* + * Also skip otherwise unreferenced swap + * objects backing tmpfs vnodes, and POSIX or + * SysV shared memory. + */ + continue; + } total.t_vm += object->size; total.t_rm += object->resident_page_count; - if (object->flags & OBJ_ACTIVE) { + if (is_object_active(object)) { total.t_avm += object->size; total.t_arm += object->resident_page_count; } @@ -212,7 +204,7 @@ vmtotal(SYSCTL_HANDLER_ARGS) /* shared object */ total.t_vmshr += object->size; total.t_rmshr += object->resident_page_count; - if (object->flags & OBJ_ACTIVE) { + if (is_object_active(object)) { total.t_avmshr += object->size; total.t_armshr += object->resident_page_count; } Modified: head/sys/vm/vm_object.h ============================================================================== --- head/sys/vm/vm_object.h Tue Jun 21 15:49:09 2016 (r302062) +++ head/sys/vm/vm_object.h Tue Jun 21 17:49:33 2016 (r302063) @@ -182,7 +182,6 @@ struct vm_object { */ #define OBJ_FICTITIOUS 0x0001 /* (c) contains fictitious pages */ #define OBJ_UNMANAGED 0x0002 /* (c) contains unmanaged pages */ -#define OBJ_ACTIVE 0x0004 /* active objects */ #define OBJ_DEAD 0x0008 /* dead objects (during rundown) */ #define OBJ_NOSPLIT 0x0010 /* dont split this object */ #define OBJ_UMTXDEAD 0x0020 /* umtx pshared was terminated */