From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D145A25A2CE; Wed, 19 Feb 2025 21:36:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740000968; cv=none; b=SyghCiFYcYp4QMUnjPkTLZvaDvSYRx/Igsj7KaxediJfFcbWXH+aI1ZdP4plSgQViJe6bX0Def3FqiH+APwdMVU9y4kt18DJ41Wd2YoozfJhEVmHefEltLgOsarmSZFLIn47rlHVPNvBz5VPmUCexMTdwJAdvhhXUSo1+hpIkt4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740000968; c=relaxed/simple; bh=H8cW+KqFza/9wuv7O8fJzMx0LlSrfigkACT10J58gp0=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=ItVvNDK6AkQ8AEAtmQg7It6KAim0EnksC0LRCc+2HAFbMXIG/M5caih+2c7LSaz5CIER/a9/9TrDkYhMnnzRFRfIkVffmWholHMbUlq5pQgrw6L0fbdSTiO+7WD9Kr6WvSPLA+Dn4H4zj9P9SNenjV+4qeWzHt6q1Rp5r9OBmRU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=T4oki23B; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="T4oki23B" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7D845C4CEEC; Wed, 19 Feb 2025 21:36:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1740000968; bh=H8cW+KqFza/9wuv7O8fJzMx0LlSrfigkACT10J58gp0=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=T4oki23BOklJRKQRrSsBaXrq37NWTBXHfc2eQZ8rbrtekenigDrNgwdtQv8fa5lQ6 8Uqj41b6Qwb7u5iG0a//FcJ6gtmgp56YOAK8oUfVgFaX/PSwvRAs/x8a+RZB/ERbGx U/PR9GcbTvnR2xd38uEIapiTTYgDghyJ/4aCxjWa3EauahKmyLI4QRtUEeED/TByYg ys9Duj3bl7KmnJ4CWUi3uGwGWe6xgx2bEcvgG51rxyUuU5NaxoMLIJ6T9kOQBsACXQ 9gC9+mZXLqwYhTK/xFMPRUserlgFWiCyp8/ux31cjah/yzmv8z5GT38ajPCPp9Xo+M iCuFWMZWQzhsg== Date: Wed, 19 Feb 2025 13:36:07 -0800 From: Jakub Kicinski To: Greg Kroah-Hartman Cc: stable@vger.kernel.org, patches@lists.linux.dev, Eric Dumazet , Paolo Abeni , Sasha Levin Subject: Re: [PATCH 6.13 235/274] Revert "net: skb: introduce and use a single page frag cache" Message-ID: <20250219133607.03a5add6@kernel.org> In-Reply-To: <20250219082618.775483707@linuxfoundation.org> References: <20250219082609.533585153@linuxfoundation.org> <20250219082618.775483707@linuxfoundation.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Wed, 19 Feb 2025 09:28:09 +0100 Greg Kroah-Hartman wrote: > 6.13-stable review patch. If anyone has any objections, please let me know. > > ------------------ > > From: Paolo Abeni > > [ Upstream commit 011b0335903832facca86cd8ed05d7d8d94c9c76 ] > > This reverts commit dbae2b062824 ("net: skb: introduce and use a single > page frag cache"). The intended goal of such change was to counter a > performance regression introduced by commit 3226b158e67c ("net: avoid > 32 x truesize under-estimation for tiny skbs"). > > Unfortunately, the blamed commit introduces another regression for the > virtio_net driver. Such a driver calls napi_alloc_skb() with a tiny > size, so that the whole head frag could fit a 512-byte block. > > The single page frag cache uses a 1K fragment for such allocation, and > the additional overhead, under small UDP packets flood, makes the page > allocator a bottleneck. > > Thanks to commit bf9f1baa279f ("net: add dedicated kmem_cache for > typical/small skb->head"), this revert does not re-introduce the > original regression. Actually, in the relevant test on top of this > revert, I measure a small but noticeable positive delta, just above > noise level. > > The revert itself required some additional mangling due to the > introduction of the SKB_HEAD_ALIGN() helper and local lock infra in the > affected code. > > Suggested-by: Eric Dumazet > Fixes: dbae2b062824 ("net: skb: introduce and use a single page frag cache") > Signed-off-by: Paolo Abeni > Link: https://patch.msgid.link/e649212fde9f0fdee23909ca0d14158d32bb7425.1738877290.git.pabeni@redhat.com > Signed-off-by: Jakub Kicinski > Signed-off-by: Sasha Levin As already pointed out this was reverted