From owner-freebsd-net@freebsd.org Tue Mar 30 22:27:32 2021 Return-Path: Delivered-To: freebsd-net@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 9A26A5B0694 for ; Tue, 30 Mar 2021 22:27:32 +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 4F93wh3pVNz3hbD for ; Tue, 30 Mar 2021 22:27:32 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: by mailman.nyi.freebsd.org (Postfix) id 80E995B05CC; Tue, 30 Mar 2021 22:27:32 +0000 (UTC) Delivered-To: net@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 80AAC5B0691 for ; Tue, 30 Mar 2021 22:27:32 +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 "R3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4F93wh37bkz3hkW for ; Tue, 30 Mar 2021 22:27:32 +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 507656733 for ; Tue, 30 Mar 2021 22:27:32 +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 12UMRWcn085388 for ; Tue, 30 Mar 2021 22:27:32 GMT (envelope-from bugzilla-noreply@freebsd.org) Received: (from www@localhost) by kenobi.freebsd.org (8.15.2/8.15.2/Submit) id 12UMRWV9085387 for net@FreeBSD.org; Tue, 30 Mar 2021 22:27:32 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: net@FreeBSD.org Subject: [Bug 254333] [tcp] sysctl net.inet.tcp.hostcache.list hangs Date: Tue, 30 Mar 2021 22:27:32 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Base System X-Bugzilla-Component: kern X-Bugzilla-Version: 11.4-STABLE X-Bugzilla-Keywords: X-Bugzilla-Severity: Affects Many People X-Bugzilla-Who: rscheff@freebsd.org X-Bugzilla-Status: In Progress X-Bugzilla-Resolution: X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: rscheff@freebsd.org X-Bugzilla-Flags: mfc-stable13? mfc-stable12? mfc-stable11? X-Bugzilla-Changed-Fields: 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-net@freebsd.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 30 Mar 2021 22:27:32 -0000 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D254333 --- Comment #19 from Richard Scheffenegger --- (In reply to Michael Tuexen from comment #18) > Richard: Do you see a way how the counter could be off? Unfortunately not. I was thinking about adding KASSERTS when the counter is about to be decremented, but is already zero... Or simply reset all the counters to zero (hch_length, cache_count) when a purgeall is being performed, to return to a "known good" state. The only feasible way I can thing of right now, would be if the hostcache settings are changed dynamically, while the hostcache is already populated = with some entries. That may leave the hc_bucket full, but the counters off... But all the normal processing of the accounting variables look good. > But tcp_hc_purge_internal() decrements the counter when it removes an > entry and frees it. I double checked the code and I think the counter > is handled correctly. I did look for an underflow, but I could not > find it... > I also looked at the 11.4 code, but I see no issue. The diff between 11.4 and HEAD is minuscle. None of the logic has changed (meaning this very same issue could potentially still be impacting HEAD). > If the hash buckets are used highly un-symmetric, I wouldn't suggest > to use larger buckets. That results in long processing time. In that > case I would suggest to use a better hash algorithm. But this is not > the issue right now. Correct. (A different salt during hashing may also help. Frequently used entries do percholate to the head of the TAILQ, though.) > For the counter having such a large value could happen when there is > an underflow. But I don't see how it can happen. For me it looks like > the global and the bucket counter are handled correctly.=20 Still, a underflow is more likely than an overflow. > Since the statement is that this happens every 3 to 4 month, it must > be a rare event. Or some other code is writing in the memory location > where the counter is... KASSERTS for safety? (And an eventual core to potentially analyze) --=20 You are receiving this mail because: You are on the CC list for the bug.=