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Re: [Qemu-devel] [PATCH v5 2/4 for-3.0] qcow2: Options' documentation fi
Re: [Qemu-devel] [PATCH v5 2/4 for-3.0] qcow2: Options' documentation fixes
Thu, 26 Jul 2018 16:46:57 +0200
Am 26.07.2018 um 16:27 hat Leonid Bloch geschrieben:
> On 07/26/2018 01:02 PM, Kevin Wolf wrote:
> > Am 25.07.2018 um 16:27 hat Leonid Bloch geschrieben:
> > > Signed-off-by: Leonid Bloch <address@hidden>
> > > ---
> > > docs/qcow2-cache.txt | 3 +++
> > > qemu-options.hx | 10 ++++++----
> > > 2 files changed, 9 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/docs/qcow2-cache.txt b/docs/qcow2-cache.txt
> > > index 8a09a5cc5f..3673f2be0e 100644
> > > --- a/docs/qcow2-cache.txt
> > > +++ b/docs/qcow2-cache.txt
> > > @@ -130,6 +130,9 @@ 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.
> > > +- At most two of "l2-cache-size", "refcount-cache-size", and "cache-size"
> > > + can be set simultaneously.
> > The indentation is off here, the other list items have one space more.
> > > 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
> > > diff --git a/qemu-options.hx b/qemu-options.hx
> > > index b1bf0f485f..13ece21cb6 100644
> > > --- a/qemu-options.hx
> > > +++ b/qemu-options.hx
> > > @@ -752,15 +752,17 @@ image file)
> > > @item cache-size
> > > The maximum total size of the L2 table and refcount block caches in
> > > bytes
> > > -(default: 1048576 bytes or 8 clusters, whichever is larger)
> > I think it would be good to still say something about the default.
> > Maybe something like "default: the sum of l2-cache-size and
> > refcount-cache-size"?
> Yes, that sounds good!
> > > @item l2-cache-size
> > > -The maximum size of the L2 table cache in bytes
> > > -(default: 4/5 of the total cache size)
> > > +The maximum size of the L2 table cache.
> > Why did you remove "in bytes" and add a period which the other options
> > don't have? I prefer the old version of this line.
> I removed "in bytes" because it also accepts k, M, G, ... but on a second
> thought, these are amounts of bytes as well, so changing back to the old
> > > +(default: if cache-size is not defined - 1048576 bytes or 8 clusters,
> > > whichever
> > > +is larger; otherwise, as large as possible or needed within the
> > > cache-size,
> > > +while permitting the requested or the minimal refcount cache size)
> > > @item refcount-cache-size
> > > The maximum size of the refcount block cache in bytes
> > > -(default: 1/5 of the total cache size)
> > > +(default: 4 times the cluster size, or any portion of the cache-size, if
> > > it is
> > > +specified and large enough, left over after allocating the full L2 cache)
> > I found the second part hard to understand. Maybe "4 times the cluster
> > size; or if both cache-size and l2-cache-size are given, the part of
> > the cache-size that is not used for the L2 cache yet."?
> That is not accurate. Because even if l2-cache-size is not given and
> cache-size is large enough to accommodate enough L2 cache to cover the
> entire image, plus the minimal amount of refcount cache with room to spare -
> refcount cache will use all the rest of the cache-size.
Oh, you're right! I wasn't aware that we consider the image size there.
> How about:
> "default: 4 times the cluster size; or if cache-size is specified, the part
> of it which is not used for the L2 cache"
Even simpler, easier to understand and more accurate. I like it.
[Qemu-devel] [PATCH v5 3/4] qcow2: Introduce an option for sufficient L2 cache for the entire image, Leonid Bloch, 2018/07/25
[Qemu-devel] [PATCH v5 4/4] iotests: Add tests for the new l2-cache-full option, Leonid Bloch, 2018/07/25