[edk2-devel] [PATCH 2/8] OvmfPkg: raise PcdShellFileOperationSize to 128KB

[Laszlo Ersek]

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 at arm.com>
Cc: Jordan Justen <jordan.l.justen at intel.com>
Cc: Philippe Mathieu-Daudé <philmd at redhat.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3125
Signed-off-by: Laszlo Ersek <lersek at redhat.com>
---
 OvmfPkg/OvmfPkgIa32.dsc    | 2 ++
 OvmfPkg/OvmfPkgIa32X64.dsc | 2 ++
 OvmfPkg/OvmfPkgX64.dsc     | 2 ++
 3 files changed, 6 insertions(+)

diff --git a/OvmfPkg/OvmfPkgIa32.dsc b/OvmfPkg/OvmfPkgIa32.dsc
index 26a013ec353e..cd0acf021459 100644
--- a/OvmfPkg/OvmfPkgIa32.dsc
+++ b/OvmfPkg/OvmfPkgIa32.dsc
@@ -560,6 +560,8 @@ [PcdsFixedAtBuild]
   #
 !include NetworkPkg/NetworkPcds.dsc.inc
 
+  gEfiShellPkgTokenSpaceGuid.PcdShellFileOperationSize|0x20000
+
 !if $(SMM_REQUIRE) == TRUE
   gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmStackSize|0x4000
 !endif
diff --git a/OvmfPkg/OvmfPkgIa32X64.dsc b/OvmfPkg/OvmfPkgIa32X64.dsc
index 10579fe46c5b..3bf493bdb08f 100644
--- a/OvmfPkg/OvmfPkgIa32X64.dsc
+++ b/OvmfPkg/OvmfPkgIa32X64.dsc
@@ -566,6 +566,8 @@ [PcdsFixedAtBuild.X64]
   #
 !include NetworkPkg/NetworkPcds.dsc.inc
 
+  gEfiShellPkgTokenSpaceGuid.PcdShellFileOperationSize|0x20000
+
 !if $(SMM_REQUIRE) == TRUE
   gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmStackSize|0x4000
 !endif
diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc
index c9235e48ad62..cebdbc9faabe 100644
--- a/OvmfPkg/OvmfPkgX64.dsc
+++ b/OvmfPkg/OvmfPkgX64.dsc
@@ -564,6 +564,8 @@ [PcdsFixedAtBuild]
   #
 !include NetworkPkg/NetworkPcds.dsc.inc
 
+  gEfiShellPkgTokenSpaceGuid.PcdShellFileOperationSize|0x20000
+
 !if $(SMM_REQUIRE) == TRUE
   gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmStackSize|0x4000
 !endif
-- 
2.19.1.3.g30247aa5d201




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