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authorLaszlo Ersek <lersek@redhat.com>2021-01-13 09:54:45 +0100
committermergify[bot] <37929162+mergify[bot]@users.noreply.github.com>2021-01-19 18:23:28 +0000
commit2912341cd924ebc32889879912aa9588dae4d209 (patch)
treef8062bed2c2e785868123ad7d1d2ba14959c2fb2 /ArmVirtPkg/ArmVirtQemuKernel.dsc
parentf72fd9616eedac9a521adcbbe5086dd666c67232 (diff)
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OvmfPkg: raise PcdShellFileOperationSize to 128KB
Some UEFI shell commands read and write files in chunks. The chunk size is given by "PcdShellFileOperationSize", whose default in "ShellPkg/ShellPkg.dec" is 4KB (0x1000). The virtio-fs daemon of QEMU advertizes a 128KB maximum buffer size by default, for the FUSE_WRITE operation. By raising PcdShellFileOperationSize 32-fold, the number of FUSE write requests shrinks proportionately, when writing large files. And when a Virtio Filesystem is not used, a 128KB chunk size is still not particularly wasteful. Some ad-hoc measurements on my laptop, using OVMF: - The time it takes to copy a ~270MB file from a Virtio Filesystem to the same Virtio Filesystem improves from ~9 seconds to ~1 second. - The time it takes to compare two identical ~270MB files on the same Virtio Filesystem improves from ~11 seconds to ~3 seconds. Cc: Ard Biesheuvel <ard.biesheuvel@arm.com> Cc: Jordan Justen <jordan.l.justen@intel.com> Cc: Philippe Mathieu-Daudé <philmd@redhat.com> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3125 Signed-off-by: Laszlo Ersek <lersek@redhat.com> Acked-by: Ard Biesheuvel <ard.biesheuvel@arm.com> Message-Id: <20210113085453.10168-3-lersek@redhat.com> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
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