From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f182.google.com (mail-pl1-f182.google.com [209.85.214.182]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8064F1E52C for ; Tue, 30 Apr 2024 21:37:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.182 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714513030; cv=none; b=P3GQ4jR4jJjevtXytj4uLpKtC71qqdZCTKCenLvtoo+4/Vz8Vk+Ycfid+BdwBfYxji7mGLrHeFSRd7QBJbgwQV+QDWjUdkeeBKt4HsO5NJFlPobeor8j7JoDHBx4tzC78YewfBGPvcqA77sA1+tVezBl06R1QpTGbQXsq2ebv3E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714513030; c=relaxed/simple; bh=kOVBn+L8m+KGx+xWui9qhwHE48LPdqGInZLL5XjNFQI=; h=From:To:Cc:In-Reply-To:References:Subject:Message-Id:Date: MIME-Version:Content-Type; b=EMWxcKgvJChotYDpqWu2MCd/Tm9p4AH2i4/j9+l/xaKnyHSAFd2IblIwXWGxHR9W7eqK93AXKDKzOYFoZCXlVEJFEnioHtz6e8/K5TqK4i5eQxma6mbmTitbEdP/54f7bLlMmUeSgrvUuLWL0uSkoTcuzIGYjWjoCwm540ZRuyY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.dk; spf=pass smtp.mailfrom=kernel.dk; dkim=pass (2048-bit key) header.d=kernel-dk.20230601.gappssmtp.com header.i=@kernel-dk.20230601.gappssmtp.com header.b=cb4m8sR5; arc=none smtp.client-ip=209.85.214.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.dk Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=kernel.dk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20230601.gappssmtp.com header.i=@kernel-dk.20230601.gappssmtp.com header.b="cb4m8sR5" Received: by mail-pl1-f182.google.com with SMTP id d9443c01a7336-1e4edcde7a1so1168245ad.0 for ; Tue, 30 Apr 2024 14:37:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20230601.gappssmtp.com; s=20230601; t=1714513027; x=1715117827; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:date:message-id:subject :references:in-reply-to:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=fsXDFuZiyvVk+tVFuwao6+tHBHPTn4kHu7I5bTNLw68=; b=cb4m8sR5tKjHECuSToVPA9/glaCGh0KUDNjOU9rnA+legAFdjnT3+up1WBJpRrfDRf aezUBqIGURfBHmYM/KsfX15F3VjJNI2i4+gqwcbds9bnunv4e9qUhBcsWeQfZWcOC7d5 P8+ORaGcdoxnHYX7TJPrMsGtxoS1hlkXuHtfL7S8IlOsehO0st5xS81Rd7FQ4hm7oveK 9H9fmxB5FI+NhXDxvLhkHvWLhTOrkm1AQZmOo8nfCFfwEOrQWFrFl8Zw/NQdYr3gHtr2 LQuZTDG/jvJN9jn7qsQdQcyQepzQR/pJdrtfJfW8exj/QxyFUo2iqe8X+vzeR9XiDQ95 bMaw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1714513027; x=1715117827; h=content-transfer-encoding:mime-version:date:message-id:subject :references:in-reply-to:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=fsXDFuZiyvVk+tVFuwao6+tHBHPTn4kHu7I5bTNLw68=; b=ExVClOcbw/mmN8hBglIK9Fl7RTbJx+S30rpDhc7Z4jDKw74NNOSlPRJSMbkPqUoWn7 vTu2mkfqM00zAeokqMjNqS+jY14er8b4Co+SueHmOgXifCvn7H3OMqHAU3/xO8CYwO22 Bld0yygK/MZhglzadtRo0AHG3B1wLetHLv8nCAl+YdkREU0dT+sMEW0r1xkDwA4lBToG p16XO3+tWaW/8Az2SITaLhRn7KaS1B1hvwaEwGAbbuIHUMEvgPBIi5IP/dzKRqlvMUsU P/bbIX5fZWC3c4XewbhoO0ImSkz/eGx84P/7JyCAlrX8lS8jV2ygdvnp88xNno2OMTF5 +cow== X-Gm-Message-State: AOJu0YxFTsLlZrk3oLtfbYd0hgRA6ShMmbR6KtjbSQK6ntAbmpWIBKsB /2CSCTCzgZgIE5RvXRvXCc2QGTFZxUYU3XJRRz7J+vedLnmhB8h+5chbnedgY8n1UiEH0v+N9J6 8 X-Google-Smtp-Source: AGHT+IFskMVR2XTWlnojk5XC5/Xi3NVEgsWVudcqnuGTpHqfDXnpj2j+qOh9W7M7C5ZyxQI/KXyJtA== X-Received: by 2002:a17:902:da83:b0:1dd:b54c:df51 with SMTP id j3-20020a170902da8300b001ddb54cdf51mr681464plx.4.1714513026759; Tue, 30 Apr 2024 14:37:06 -0700 (PDT) Received: from [127.0.0.1] ([198.8.77.194]) by smtp.gmail.com with ESMTPSA id c21-20020a170902b69500b001ec70d2b5fesm787701pls.197.2024.04.30.14.37.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 30 Apr 2024 14:37:05 -0700 (PDT) From: Jens Axboe To: Ming Lei , Christoph Hellwig , Uday Shankar Cc: linux-block@vger.kernel.org, Riley Thomasson In-Reply-To: <20240430211623.2802036-1-ushankar@purestorage.com> References: <20240430211623.2802036-1-ushankar@purestorage.com> Subject: Re: [PATCH v2] ublk: remove segment count and size limits Message-Id: <171451302531.24801.16357937130261445082.b4-ty@kernel.dk> Date: Tue, 30 Apr 2024 15:37:05 -0600 Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Mailer: b4 0.12.5-dev-2aabd On Tue, 30 Apr 2024 15:16:24 -0600, Uday Shankar wrote: > ublk_drv currently creates block devices with the default max_segments > and max_segment_size limits of BLK_MAX_SEGMENTS (128) and > BLK_MAX_SEGMENT_SIZE (65536) respectively. These defaults can > artificially constrain the I/O size seen by the ublk server - for > example, suppose that the ublk server has configured itself to accept > I/Os up to 1M and the application is also issuing 1M sized I/Os. If the > I/O buffer used by the application is backed by 4K pages, the buffer > could consist of up to 1M / 4K = 256 physically discontiguous segments > (even if the buffer is virtually contiguous). As such, the I/O could > exceed the default max_segments limit and get split. This can cause > unnecessary performance issues if the ublk server is optimized to handle > 1M I/Os. The block layer's segment count/size limits exist to model > hardware constraints which don't exist in ublk_drv's case, so just > remove those limits for the block devices created by ublk_drv. > > [...] Applied, thanks! [1/1] ublk: remove segment count and size limits commit: eaf4a9b19b9961f8ca294c39c5f8984a4cf42212 Best regards, -- Jens Axboe