From nobody Wed Oct 28 20:41:30 2026 X-Original-To: dev-commits-src-all@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4jFK5k6QrJz6x6d3 for ; Wed, 28 Oct 2026 20:41:30 +0000 (UTC) (envelope-from git@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) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id 4jFK5k2ySNz4b9N for ; Wed, 28 Oct 2026 20:41:30 +0000 (UTC) (envelope-from git@FreeBSD.org) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1793220090; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=BeMVGKTKxzf6wQU42I3siJQ6J8tP2GH5iMjs5U4fWK0=; b=g7NZljJhxvSEuUtG3aOIgSntnBSArRxqk8IojZ0MH4M+NCzt5VYlqy9yOQePmj2OdhYllZ qkyPfIHS/JzopWmQojbh5n2g7DeCiNddLOA5CedpaFKU5ymHhuAeifEN9mnWEow0M11lUV 0qYR59Han19INore/a8eH8/f+A2sAKdf0pBDimBuwpi+nGXoC9huXSaTr2Dkz9R05HfQg/ SyRXH1sn27p/ghdkrycTSLjTJi8B93+SmhXO/cSwF23zyf5qZrNmtZC//CMvcBjue2D4M6 pbj7Viejgy7PyJYqOMvGngxcejSfYgyOhinE55yKqqgDQFQcu4ArMqDH7/gA6Q== ARC-Seal: i=1; a=rsa-sha256; d=freebsd.org; s=dkim; cv=none; t=1793220090; b=pLoy3NKzLOOvRW7BxU7WCohEMEqUvLRPGphooHjHyA3BC29M5EaSbINEvI6zC6Fh6G8/ww fXlFwqU3ywgp6stH3VkPPfoQWjCTlhVtd3w+QxuBUyBrf6rGDRQRynjwYjY/Ob4GMB0m3s z/FSrdmZneET99cnX3vqo/h6rETRI1wvAMMvic/gQWFmjGp6QSVdjHE8WDmkfnq9svLjPi mHySsI64EdX8i6VST6guK/nXXJwK9f/m7QQVk1d2yppWDOgxnPXVOf9aDZBGxcUxlB3bN1 IDeaYdvVHxgfNEm1MrQY2V7JKTTLgnFaktqhPT4lAeNVdkfqbm5Yx3cc6227ng== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1793220090; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=BeMVGKTKxzf6wQU42I3siJQ6J8tP2GH5iMjs5U4fWK0=; b=E8NrYqgX8P3Spitm9M5EeDj4KPhkA99VmIDtIUPDapKUbzULjuc/6x6oS0Z7ymbfvdT3HZ voo9wz4R6R36VJ6et++4oFK7LUL0n3bSUXWAJVq+Xh+XmfjF/GMLOAn/Gr1IFOPPbwVOnm VyZWH6E0BRBA9+jd+ux0lq3CKeq6na9nK7FS4siZMwI/gGyiknhulbldROnutFRhwtXE2f C0fnp/VN6jOo/lz6CJUbMgEDgrvComwqCICf+TTvU/+cLbWNEZdQKydJz/gpVBWldwW4hw D8SIzcjq0t4vPov7cgYNB1rDSc8MXqlEdSZw90ChhP0l+SBHFqyoZRccmg5s1A== ARC-Authentication-Results: i=1; mx1.freebsd.org; none Received: from gitrepo.freebsd.org (gitrepo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:5]) by mxrelay.nyi.freebsd.org (Postfix) with ESMTP id 4jFK5k26sjz1N5l for ; Wed, 28 Oct 2026 20:41:30 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from git (uid 1279) (envelope-from git@FreeBSD.org) id 1e23e by gitrepo.freebsd.org (DragonFly Mail Agent v0.13+ on gitrepo.freebsd.org); Wed, 28 Oct 2026 20:41:30 +0000 To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org From: R. Christian McDonald Subject: git: 55153512e9ab - stable/14 - iflib: Do not ring the transmit doorbell when nothing is pending List-Archive: https://lists.freebsd.org/archives/dev-commits-src-all X-BeenThere: dev-commits-src-all@freebsd.org Sender: owner-dev-commits-src-all@FreeBSD.org List-Id: Commit messages for all branches of the src repository List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Git-Committer: rcm X-Git-Repository: src X-Git-Refname: refs/heads/stable/14 X-Git-Reftype: branch X-Git-Commit: 55153512e9abd9ec4daa7888a6a62fc8038d70ce Auto-Submitted: auto-generated Date: Wed, 28 Oct 2026 20:41:30 +0000 Message-Id: <6ae25dfa.1e23e.6123c3bf@gitrepo.freebsd.org> The branch stable/14 has been updated by rcm: URL: https://cgit.FreeBSD.org/src/commit/?id=55153512e9abd9ec4daa7888a6a62fc8038d70ce commit 55153512e9abd9ec4daa7888a6a62fc8038d70ce Author: R. Christian McDonald AuthorDate: 2026-10-05 15:17:13 +0000 Commit: R. Christian McDonald CommitDate: 2026-10-28 20:38:05 +0000 iflib: Do not ring the transmit doorbell when nothing is pending For a lightly used ring iflib_txd_db_check() may defer zero descriptors, so its "pending >= limit" test is true even when nothing has been queued since the last doorbell. iflib_txq_drain() calls it before, inside and after its loop, so a sender that drains its own packet wrote the tail register three times per packet, twice with the value the hardware already had. The log of 81be655266fa ("iflib: ensure that tx interrupts enabled and cleanups") calls skipping the doorbell when db_pending is zero "an obvious missing optimization"; the comparison against a limit of zero defeated it. vmx(4) and mgb(4) have dropped such repeated requests in the driver since 2019. Return early when nothing is pending. Reviewed by: gallatin MFC after: 2 weeks Sponsored by: Rubicon Communications, LLC ("Netgate") Differential Revision: https://reviews.freebsd.org/D60290 (cherry picked from commit 4a0ec469934a5de60b9b540689703a698ac44105) --- sys/net/iflib.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/sys/net/iflib.c b/sys/net/iflib.c index e90709e84e6f..ed2813458ebe 100644 --- a/sys/net/iflib.c +++ b/sys/net/iflib.c @@ -3134,6 +3134,13 @@ iflib_txd_db_check(iflib_txq_t txq, int ring) if_ctx_t ctx = txq->ift_ctx; qidx_t dbval, max; + /* + * Nothing has been queued since the last doorbell. The threshold is + * zero for a lightly used ring, so the test below would not catch this. + */ + if (txq->ift_db_pending == 0) + return (false); + max = TXQ_MAX_DB_DEFERRED(txq, txq->ift_in_use); /* force || threshold exceeded || at the edge of the ring */