From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43192) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fi0iQ-00019T-0y for qemu-devel@nongnu.org; Tue, 24 Jul 2018 13:03:15 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fi0iM-0004w5-O3 for qemu-devel@nongnu.org; Tue, 24 Jul 2018 13:03:14 -0400 From: Leonid Bloch Date: Tue, 24 Jul 2018 20:02:17 +0300 Message-Id: <20180724170217.10247-3-lbloch@janustech.com> In-Reply-To: <20180724170217.10247-1-lbloch@janustech.com> References: <20180724170217.10247-1-lbloch@janustech.com> MIME-Version: 1.0 Content-Type: text/plain Subject: [Qemu-devel] [PATCH v2 2/2] docs: Document the l2-cache-full option List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: qemu-block@nongnu.org, Kevin Wolf , Max Reitz , Eric Blake , Leonid Bloch This documents the new "l2-cache-full" option, and sharpens the documentation of the related options. Signed-off-by: Leonid Bloch --- docs/qcow2-cache.txt | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/docs/qcow2-cache.txt b/docs/qcow2-cache.txt index 8a09a5cc5f..ea61585a4b 100644 --- a/docs/qcow2-cache.txt +++ b/docs/qcow2-cache.txt @@ -110,11 +110,12 @@ How to configure the cache sizes Cache sizes can be configured using the -drive option in the command-line, or the 'blockdev-add' QMP command. -There are three options available, and all of them take bytes: +There are four options available: -"l2-cache-size": maximum size of the L2 table cache -"refcount-cache-size": maximum size of the refcount block cache -"cache-size": maximum size of both caches combined +"l2-cache-size": maximum size of the L2 table cache (bytes, K, M) +"refcount-cache-size": maximum size of the refcount block cache (bytes, K, M) +"cache-size": maximum size of both caches combined (bytes, K, M) +"l2-cache-full": make the L2 cache cover the full image (boolean) There are a few things that need to be taken into account: @@ -130,6 +131,15 @@ There are a few things that need to be taken into account: memory as possible to the L2 cache before increasing the refcount cache size. +- If "l2-cache-full" is specified, QEMU will assign enough memory + to the L2 cache to cover the entire size of the image. + +- "l2-cache-size" and "l2-cache-full" can not be set simultaneously, as + setting "l2-cache-full" already implies a specific size for the L2 cache. + +- All three "l2-cache-size", "refcount-cache-size", and "cache-size" options + can not be set simultaneously. + Unlike L2 tables, refcount blocks are not used during normal I/O but only during allocations and internal snapshots. In most cases they are accessed sequentially (even during random guest I/O) so increasing the -- 2.14.1