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[Qemu-block] [PATCH v2 2/2] docs: Document the l2-cache-full option
From: |
Leonid Bloch |
Subject: |
[Qemu-block] [PATCH v2 2/2] docs: Document the l2-cache-full option |
Date: |
Tue, 24 Jul 2018 20:02:17 +0300 |
This documents the new "l2-cache-full" option, and sharpens the
documentation of the related options.
Signed-off-by: Leonid Bloch <address@hidden>
---
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