Alberto García

O Grove (Spain)

One of the founding members of Igalia, Alberto loves computing since he got his first ZX Spectrum in the early nineties.

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Alberto García 16/11/2017

“Improving the performance of the qcow2 format” at KVM Forum 2017

I was in Prague last month for the 2017 edition of the KVM Forum. There I gave a talk about some of the work that I’ve been doing this year to improve the qcow2 file format used by QEMU for storing disk images. The focus of my work is to make qcow2...

Alberto García 08/02/2017

QEMU and the qcow2 metadata checks

When choosing a disk image format for your virtual machine one of the factors to take into considerations is its I/O performance. In this post I’ll talk a bit about the internals of qcow2 and about one of the aspects that can affect its performance...

Alberto García 24/05/2016

I/O bursts with QEMU 2.6

QEMU 2.6 was released a few days ago. One new feature that I have been working on is the new way to configure I/O limits in disk drives to allow bursts and increase the responsiveness of the virtual machine. In this post I’ll try to explain how it...

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qcow2: Reset free_cluster_index when allocating a new refcount block

qcow2: Reset free_cluster_index when allocating a new refcount block When we try to allocate new clusters we first look for available ones starting from s->free_cluster_index and once we find them we increase their reference counts. Before we get to...

Alberto García02/04/2018

iotests: Tweak 030 in order to trigger a race condition with parallel…

iotests: Tweak 030 in order to trigger a race condition with parallel jobs This patch tweaks TestParallelOps in iotest 030 so it allocates data in smaller regions (256KB/512KB instead of 512KB/1MB) and the block-stream job in test_stream_commit() only...

Alberto García02/04/2018

qcow2: Make qemu-img check detect corrupted L1 tables in snapshots

qcow2: Make qemu-img check detect corrupted L1 tables in snapshots 'qemu-img check' cannot detect if a snapshot's L1 table is corrupted. This patch checks the table's offset and size and reports corruption if the values are not...

Alberto García02/04/2018

qcow2: Check snapshot L1 table in qcow2_snapshot_delete()

qcow2: Check snapshot L1 table in qcow2_snapshot_delete() This function deletes a snapshot from disk, removing its entry from the snapshot table, freeing its L1 table and decreasing the refcounts of all clusters. The L1 table offset and size are...

Alberto García02/04/2018

qcow2: Check snapshot L1 table in qcow2_snapshot_goto()

qcow2: Check snapshot L1 table in qcow2_snapshot_goto() This function copies a snapshot's L1 table into the active one without validating it first. We now have a function to take care of this, so let's use it. Cc: Eric Blake Signed-off-by:...

Alberto García02/04/2018