Emilio G. Cota <c...@braap.org> writes:
> Currently we evict an entry to the victim TLB when it doesn't match > the current address. But it could be that there's no match because > the current entry is empty (i.e. all -1's, for instance via tlb_flush). > Do not evict the entry to the vtlb in that case. > > This change will help us keep track of the TLB's use rate. > > Signed-off-by: Emilio G. Cota <c...@braap.org> Reviewed-by: Alex Bennée <alex.ben...@linaro.org> > --- > include/exec/cpu-all.h | 9 +++++++++ > accel/tcg/cputlb.c | 2 +- > 2 files changed, 10 insertions(+), 1 deletion(-) > > diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h > index 117d2fbbca..e21140049b 100644 > --- a/include/exec/cpu-all.h > +++ b/include/exec/cpu-all.h > @@ -362,6 +362,15 @@ static inline bool tlb_hit(target_ulong tlb_addr, > target_ulong addr) > return tlb_hit_page(tlb_addr, addr & TARGET_PAGE_MASK); > } > > +/** > + * tlb_entry_is_empty - return true if the entry is not in use > + * @te: pointer to CPUTLBEntry > + */ > +static inline bool tlb_entry_is_empty(const CPUTLBEntry *te) > +{ > + return te->addr_read == -1 && te->addr_write == -1 && te->addr_code == > -1; > +} > + > void dump_exec_info(FILE *f, fprintf_function cpu_fprintf); > void dump_opcount_info(FILE *f, fprintf_function cpu_fprintf); > #endif /* !CONFIG_USER_ONLY */ > diff --git a/accel/tcg/cputlb.c b/accel/tcg/cputlb.c > index 80406f1033..4dc47e603c 100644 > --- a/accel/tcg/cputlb.c > +++ b/accel/tcg/cputlb.c > @@ -689,7 +689,7 @@ void tlb_set_page_with_attrs(CPUState *cpu, target_ulong > vaddr, > * Only evict the old entry to the victim tlb if it's for a > * different page; otherwise just overwrite the stale data. > */ > - if (!tlb_hit_page_anyprot(te, vaddr_page)) { > + if (!tlb_hit_page_anyprot(te, vaddr_page) && !tlb_entry_is_empty(te)) { > unsigned vidx = env->vtlb_index++ % CPU_VTLB_SIZE; > CPUTLBEntry *tv = &env->tlb_v_table[mmu_idx][vidx]; -- Alex Bennée