[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [xen master] x86/IO-APIC: Drop function pointers from __ioapic_{read,write}_entry()
commit 245a320ce22752562c2143d0fb406aeb2e334dfb Author: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> AuthorDate: Sun Oct 31 00:03:56 2021 +0100 Commit: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> CommitDate: Mon Nov 29 13:53:05 2021 +0000 x86/IO-APIC: Drop function pointers from __ioapic_{read,write}_entry() Function pointers are expensive, and the raw parameter is a constant at the root of all call trees, meaning that it predicts very well with local branch history. Furthermore, the knock-on effects are quite impressive. $ ../scripts/bloat-o-meter xen-syms-before xen-syms-after add/remove: 0/4 grow/shrink: 3/9 up/down: 459/-823 (-364) Function old new delta __ioapic_write_entry 73 286 +213 __ioapic_read_entry 75 276 +201 save_IO_APIC_setup 182 227 +45 eoi_IO_APIC_irq 241 229 -12 disable_IO_APIC 296 280 -16 mask_IO_APIC_setup 272 240 -32 __io_apic_write 46 - -46 __io_apic_read 46 - -46 io_apic_set_pci_routing 985 930 -55 __io_apic_eoi.part 223 161 -62 io_apic_write 69 - -69 io_apic_read 69 - -69 restore_IO_APIC_setup 325 253 -72 ioapic_guest_write 1413 1333 -80 clear_IO_APIC_pin 447 343 -104 setup_IO_APIC 5148 4988 -160 Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx> --- xen/arch/x86/io_apic.c | 30 ++++++++++++++++++++++-------- 1 file changed, 22 insertions(+), 8 deletions(-) diff --git a/xen/arch/x86/io_apic.c b/xen/arch/x86/io_apic.c index c3ad9efac8..1c49a0fe14 100644 --- a/xen/arch/x86/io_apic.c +++ b/xen/arch/x86/io_apic.c @@ -235,11 +235,19 @@ union entry_union { struct IO_APIC_route_entry __ioapic_read_entry( unsigned int apic, unsigned int pin, bool raw) { - unsigned int (*read)(unsigned int, unsigned int) - = raw ? __io_apic_read : io_apic_read; union entry_union eu; - eu.w1 = (*read)(apic, 0x10 + 2 * pin); - eu.w2 = (*read)(apic, 0x11 + 2 * pin); + + if ( raw ) + { + eu.w1 = __io_apic_read(apic, 0x10 + 2 * pin); + eu.w2 = __io_apic_read(apic, 0x11 + 2 * pin); + } + else + { + eu.w1 = io_apic_read(apic, 0x10 + 2 * pin); + eu.w2 = io_apic_read(apic, 0x11 + 2 * pin); + } + return eu.entry; } @@ -259,12 +267,18 @@ void __ioapic_write_entry( unsigned int apic, unsigned int pin, bool raw, struct IO_APIC_route_entry e) { - void (*write)(unsigned int, unsigned int, unsigned int) - = raw ? __io_apic_write : io_apic_write; union entry_union eu = { .entry = e }; - (*write)(apic, 0x11 + 2*pin, eu.w2); - (*write)(apic, 0x10 + 2*pin, eu.w1); + if ( raw ) + { + __io_apic_write(apic, 0x11 + 2 * pin, eu.w2); + __io_apic_write(apic, 0x10 + 2 * pin, eu.w1); + } + else + { + io_apic_write(apic, 0x11 + 2 * pin, eu.w2); + io_apic_write(apic, 0x10 + 2 * pin, eu.w1); + } } static void ioapic_write_entry( -- generated by git-patchbot for /home/xen/git/xen.git#master
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