| Message ID | 20190114165017.27298-2-cota@braap.org |
|---|---|
| State | New |
| Headers | show |
| Series | Dynamic TLB sizing | expand |
Emilio G. Cota <cota@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, which > we'll use to implement a policy for dynamic TLB sizing. > > Reviewed-by: Alex Bennée <alex.bennee@linaro.org> > Reviewed-by: Richard Henderson <richard.henderson@linaro.org> > Signed-off-by: Emilio G. Cota <cota@braap.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; > +} > + This breaks on a --disable-tcg build. I think the whole block needs to be in a: #if !defined(CONFIG_USER_ONLY) && defined(CONFIG_TCG) now. > 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 af6bd8ccf9..5dc97212a9 100644 > --- a/accel/tcg/cputlb.c > +++ b/accel/tcg/cputlb.c > @@ -591,7 +591,7 @@ 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->tlb_d[mmu_idx].vindex++ % CPU_VTLB_SIZE; > CPUTLBEntry *tv = &env->tlb_v_table[mmu_idx][vidx]; -- Alex Bennée
On Wed, Jan 16, 2019 at 10:32:08 +0000, Alex Bennée wrote: > > Emilio G. Cota <cota@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, which > > we'll use to implement a policy for dynamic TLB sizing. > > > > Reviewed-by: Alex Bennée <alex.bennee@linaro.org> > > Reviewed-by: Richard Henderson <richard.henderson@linaro.org> > > Signed-off-by: Emilio G. Cota <cota@braap.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; > > +} > > + > > This breaks on a --disable-tcg build. I think the whole block needs to > be in a: > > #if !defined(CONFIG_USER_ONLY) && defined(CONFIG_TCG) > > now. Good catch, thanks! I'll send a v7 with this fixed. Thanks, E.
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 af6bd8ccf9..5dc97212a9 100644 --- a/accel/tcg/cputlb.c +++ b/accel/tcg/cputlb.c @@ -591,7 +591,7 @@ 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->tlb_d[mmu_idx].vindex++ % CPU_VTLB_SIZE; CPUTLBEntry *tv = &env->tlb_v_table[mmu_idx][vidx];