From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 C29B31F868C for ; Tue, 21 Jan 2025 21:45:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737495956; cv=none; b=UHUZIXebJSSj1WQxxCWPJrsyOBerEQIqzlzkz6SBm9U5CgnXZhSS+/TU60Oib4wdCnnas1XtwykR3JpmiVLznXf5vGczZm1L/P8KaqkE1jthcflKddhXxz51TrZa5WlSM2bz+E3psgL9WgLBkLGxaUSqVSlMxQHLyFA2H7ibakw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737495956; c=relaxed/simple; bh=nC/rz5qlNEqJaJoWOB6niUILizEUBIFAkbeVWptvRpI=; h=From:To:Cc:Subject:References:Date:Message-ID:MIME-Version: Content-Type; b=CL/ygVVTCHcSA8ZbLue72Y96spAGuhWctkbnOay+4HU/IBYsesLpTSawagUO9k/g0XAMA98hi7xE8lgKhJJ0xGjUwC38EQL3jRYj7s6QLMLrZTvhS+5Ux6IHgjMWkejPTuGAL2117m6BLbqFpEUoMlio0jm28rFOJnR/VpIyCQg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=XucRk4CW; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="XucRk4CW" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1737495953; 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: references:references; bh=3f+coA5NoWEtCA0NXXl4cQ8i/fNkiu2i2ktDHwLz0D0=; b=XucRk4CWuSPqe7cp6R7DHDkzts9vomEqX3KV1ZguneWFb25RaKMkB3oHr/l3FYbgx93por LPGzvsBEW9Rm5I8rhgVf71eeHCGzESDuC1wRng9QSVbC66eV0MkzpCzUkfbCPZSZ/IZYjj JF+wpmMpUHH1CoDbywDyXnbqRGVoVa0= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-274-IXDV195PPTOylwo7lH1lTw-1; Tue, 21 Jan 2025 16:45:49 -0500 X-MC-Unique: IXDV195PPTOylwo7lH1lTw-1 X-Mimecast-MFC-AGG-ID: IXDV195PPTOylwo7lH1lTw Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 292FB19560BB; Tue, 21 Jan 2025 21:45:48 +0000 (UTC) Received: from segfault.usersys.redhat.com (unknown [10.22.88.205]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 0E5DA195608E; Tue, 21 Jan 2025 21:45:46 +0000 (UTC) From: Jeff Moyer To: Stephen Bates Cc: linux-btrace@vger.kernel.org, axboe@kernel.dk Subject: Re: [PATCH v1 0/1] Add an option to stop blktrace based on events recorded References: X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 Date: Tue, 21 Jan 2025 16:45:44 -0500 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) Precedence: bulk X-Mailing-List: linux-btrace@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Stephen Bates writes: > Hi Jeff > >> Can you expand on the use case? Why is the number of events a useful >> parameter? >> >> Thanks, >> Jeff > > I am working on tying blktrace into a prometheus exporter so I can > monitor block-level activity across a fleet of storage servers. I > don't want to overload either the storage server CPUs or the exporter > itself when the server is under high load so I want to avoid using the > time-based argument for blktrace. > > If I have access to an events based option I can run this knowing that > in high-load situations I will not be capturing many, many IO and > perhaps slowing down the server in the process. > > Does that make sense? Yes, thanks for the clarification. Originally I thought you might be using the number of events as a proxy for the size of data collected. I'm still not sure how a user would reason about how many events is too many (or enough), but that's a not a problem for blktrace to figure out. I'll reply to the patch with my comments. Cheers, Jeff