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.

Latest Updates

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: Define and use QCOW2_COMPRESSED_SECTOR_SIZE

qcow2: Define and use QCOW2_COMPRESSED_SECTOR_SIZE When an L2 table entry points to a compressed cluster the space used by the data is specified in 512-byte sectors. This size is independent from BDRV_SECTOR_SIZE and is specific to the qcow2 file...

Alberto García20/05/2019

block: Use BDRV_REQUEST_MAX_BYTES instead of BDRV_REQUEST_MAX_SECTORS

block: Use BDRV_REQUEST_MAX_BYTES instead of BDRV_REQUEST_MAX_SECTORS There are a few places in which we turn a number of bytes into sectors in order to compare the result against BDRV_REQUEST_MAX_SECTORS instead of using BDRV_REQUEST_MAX_BYTES...

Alberto García20/05/2019

qcow2: Remove BDRVQcow2State.cluster_sectors

qcow2: Remove BDRVQcow2State.cluster_sectors The last user of this field disappeared when we replace the sector-based bdrv_write() with the byte-based bdrv_pwrite(). Signed-off-by: Alberto Garcia Reviewed-by: Vladimir Sementsov-Ogievskiy...

Alberto García13/05/2019

block: Remove bdrv_read() and bdrv_write()

block: Remove bdrv_read() and bdrv_write() No one is using these functions anymore, all callers have switched to the byte-based bdrv_pread() and bdrv_pwrite() Signed-off-by: Alberto Garcia Reviewed-by: Vladimir Sementsov-Ogievskiy Signed-off-by:...

Alberto García13/05/2019

vvfat: Replace bdrv_{read,write}() with bdrv_{pread,pwrite}()

vvfat: Replace bdrv_{read,write}() with bdrv_{pread,pwrite}() There's only a couple of bdrv_read() and bdrv_write() calls left in the vvfat code, and they can be trivially replaced with the byte-based bdrv_pread() and bdrv_pwrite(). Signed-off-by:...

Alberto García13/05/2019