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| author | Michael Brown | 2014-04-28 21:20:44 +0200 |
|---|---|---|
| committer | Michael Brown | 2014-04-29 19:24:10 +0200 |
| commit | e4593909a8a21c4a9d5766bf6a0770bcf6ee6911 (patch) | |
| tree | 4831a67764ab2ea8e9aa5210b3c9c0d3bd7e7f3a /src | |
| parent | [comboot] Use built-in interrupt reflector (diff) | |
| download | ipxe-e4593909a8a21c4a9d5766bf6a0770bcf6ee6911.tar.gz ipxe-e4593909a8a21c4a9d5766bf6a0770bcf6ee6911.tar.xz ipxe-e4593909a8a21c4a9d5766bf6a0770bcf6ee6911.zip | |
[pcbios] Do not switch to real mode to check for timer interrupt
The currticks() function is called at least once per TCP packet, and
so is performance-critical. Switching to real mode just to allow the
timer interrupt to fire is expensive when running inside a virtual
machine, and imposes a significant performance cost.
Fix by enabling interrupts without switching to real mode. This
results in an approximately 100% increase in download speed when
running under KVM.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Diffstat (limited to 'src')
| -rw-r--r-- | src/arch/i386/interface/pcbios/bios_timer.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/src/arch/i386/interface/pcbios/bios_timer.c b/src/arch/i386/interface/pcbios/bios_timer.c index 3cb8756f7..65bbf9e01 100644 --- a/src/arch/i386/interface/pcbios/bios_timer.c +++ b/src/arch/i386/interface/pcbios/bios_timer.c @@ -44,10 +44,10 @@ static unsigned long bios_currticks ( void ) { uint8_t midnight; /* Re-enable interrupts so that the timer interrupt can occur */ - __asm__ __volatile__ ( REAL_CODE ( "sti\n\t" - "nop\n\t" - "nop\n\t" - "cli\n\t" ) : : ); + __asm__ __volatile__ ( "sti\n\t" + "nop\n\t" + "nop\n\t" + "cli\n\t" ); get_real ( ticks, BDA_SEG, 0x006c ); get_real ( midnight, BDA_SEG, 0x0070 ); |