From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-184.mta1.migadu.com (out-184.mta1.migadu.com [95.215.58.184]) (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 D5A351DE894 for ; Mon, 6 Jan 2025 14:39:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.184 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736174382; cv=none; b=RAjQr76bVFdWFb07TKMXvrLmRibqaBMkH9yTIqH5qguZAvBJ3xqrtmeLQBxyIhPU3IURaOx6wlMIBFbHS+Zubp+tOVlVTpElDh0R6Su9WarSc8tXLEKOUU9NCrz7dVKatUNmaOZlmhQV5SsNBW1N0cZ/8CBxEQpzt+Zi9L0RMwI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736174382; c=relaxed/simple; bh=pEcdNS6biiuDg5Lz2TFAPdrcZP4bEIgW5De5HoGw8aA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=CA2Pl9x3dza5e6c48UY3HImLhJ+k9jHxFrooOLii7kjW9dJNJAItfibqsMo0Ra+OUTLufJLZxOqo3eXBY8EYrNhJuLTJWVzLZhhQOSCip9wOE+v1kNWHh3DF3VWD7wuStkOYSqQccYJlaNVD58LkvNO2bgIRNFgTDtc63YhZ5/I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=JLi2So6Y; arc=none smtp.client-ip=95.215.58.184 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="JLi2So6Y" Message-ID: <6c63dd3a-378d-471f-8af0-725edc3785ed@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1736174377; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=1QBb1SxSbkhq0fjJPP/D8igQzmWEtDwWTFQrDDQ04OM=; b=JLi2So6YMgc1dnvVKl8hkq5wxmbpmbt93tP9dW3JvqKloiWUhxBzIW4jWw3BIH4IdoUiuD 9wXf2ugoGGIVDR78uxu6XWy1ZOr8e/zHj8vPORYlyin6Oy6bcJETw/dBqjDwmgeLJYnrPl dmUulL7tkr6kcGySvUEWJOd+D5/Ekcs= Date: Mon, 6 Jan 2025 15:39:34 +0100 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [LSF/MM/BPF TOPIC] Improving Block Layer Tracepoints for Next-Generation Backup Systems To: Christoph Hellwig , Vishnu ks Cc: Song Liu , lsf-pc@lists.linux-foundation.org, linux-block@vger.kernel.org, bpf@vger.kernel.org, linux-nvme@lists.infradead.org References: Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Zhu Yanjun In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 06.01.25 08:37, Christoph Hellwig wrote: > On Sat, Jan 04, 2025 at 11:22:40PM +0530, Vishnu ks wrote: >> 1. Uses eBPF to monitor block_rq_complete tracepoint to track modified sectors > > You can't. Drivers can and often do change the sector during submission > processing. If I get you correctly, you mean, the action that **drivers often change the sector during submission processing** will generate a lot of tracepoint events. Thus, this will make difference on the performance of the whole system. If yes, can we only monitor fentry/fexit of some_important_key_function to reduce the eBPF events? Thus this will not generate too many events then make difference on the performance. Zhu Yanjun > >> 2. Captures sector numbers (not data) of changed blocks in real-time >> 3. Periodically syncs the actual data from these sectors based on >> configurable RPO >> 4. Layers these incremental changes on top of base snapshots > > And all of that is broken. If you are interested in this kind of > mechanism help upstreaming the blk-filter work, which has been > explicitly designed to support that. > > Before that you should really undestand how block devices and > file systems work, as the rest of the mail suggested a very dangerous > misunderstanding of the basic principles.