From owner-freebsd-bugs@freebsd.org Thu Jul 16 02:34:40 2020 Return-Path: Delivered-To: freebsd-bugs@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 219F9350C13 for ; Thu, 16 Jul 2020 02:34:40 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from mailman.nyi.freebsd.org (unknown [127.0.1.3]) by mx1.freebsd.org (Postfix) with ESMTP id 4B6dcw07Hcz3b92 for ; Thu, 16 Jul 2020 02:34:40 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: by mailman.nyi.freebsd.org (Postfix) id 047033508EC; Thu, 16 Jul 2020 02:34:40 +0000 (UTC) Delivered-To: bugs@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 043B935087E for ; Thu, 16 Jul 2020 02:34:40 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4B6dcv6P9Wz3bFS for ; Thu, 16 Jul 2020 02:34:39 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org (kenobi.freebsd.org [IPv6:2610:1c1:1:606c::50:1d]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id BF1BB21486 for ; Thu, 16 Jul 2020 02:34:39 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org ([127.0.1.5]) by kenobi.freebsd.org (8.15.2/8.15.2) with ESMTP id 06G2YdDu092895 for ; Thu, 16 Jul 2020 02:34:39 GMT (envelope-from bugzilla-noreply@freebsd.org) Received: (from www@localhost) by kenobi.freebsd.org (8.15.2/8.15.2/Submit) id 06G2YdcZ092894 for bugs@FreeBSD.org; Thu, 16 Jul 2020 02:34:39 GMT (envelope-from bugzilla-noreply@freebsd.org) X-Authentication-Warning: kenobi.freebsd.org: www set sender to bugzilla-noreply@freebsd.org using -f From: bugzilla-noreply@freebsd.org To: bugs@FreeBSD.org Subject: [Bug 248008] Post r358097 an i386 system can hang with many processes sleeping on btalloc Date: Thu, 16 Jul 2020 02:34:39 +0000 X-Bugzilla-Reason: AssignedTo X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Base System X-Bugzilla-Component: kern X-Bugzilla-Version: CURRENT X-Bugzilla-Keywords: X-Bugzilla-Severity: Affects Some People X-Bugzilla-Who: rmacklem@FreeBSD.org X-Bugzilla-Status: New X-Bugzilla-Resolution: X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: bugs@FreeBSD.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: attachments.created Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: https://bugs.freebsd.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-BeenThere: freebsd-bugs@freebsd.org X-Mailman-Version: 2.1.33 Precedence: list List-Id: Bug reports List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 16 Jul 2020 02:34:40 -0000 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D248008 --- Comment #1 from Rick Macklem --- Created attachment 216478 --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=3D216478&action= =3Dedit Ryan Libby's suggestion #2 way to fix this When doing a kernel build over NFS, I could frequently get the system hung with many processes sleeping on btalloc. Ryan Libby made the following suggestions: I think the patch is not complete. It looks like the problem is that for systems that do not have UMA_MD_SMALL_ALLOC, we do uma_zone_set_allocf(vmem_bt_zone, vmem_bt_alloc); but we haven't set an appropriate free function. This is probably why UMA_ZONE_NOFREE was originally there. When NOFREE was removed, it was appropriate for systems with uma_small_alloc. So by default we get page_free as our free function. That calls kmem_free, which calls vmem_free ... but we do our allocs with vmem_xalloc. I'm not positive, but I think the problem is that in effect we vmem_xalloc -> vmem_free, not vmem_xfree. Three possible fixes: 1: The one you tested, but this is not best for systems with uma_small_alloc. 2: Pass UMA_ZONE_NOFREE conditional on UMA_MD_SMALL_ALLOC. 3: Actually provide an appropriate vmem_bt_free function. I think we should just do option 2 with a comment, it's simple and it's what we used to do. I'm not sure how much benefit we would see from option 3, but it's more work. This patch implements #2 and seems to fix the problem. The problem was not reproducible on an amd64 system with memory set to 1Gbyte. --=20 You are receiving this mail because: You are the assignee for the bug.=