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Re: [Qemu-devel] [RFC v2 3/5] cputlb: do not evict empty entries to the
From: |
Alex Bennée |
Subject: |
Re: [Qemu-devel] [RFC v2 3/5] cputlb: do not evict empty entries to the vtlb |
Date: |
Tue, 09 Oct 2018 15:45:59 +0100 |
User-agent: |
mu4e 1.1.0; emacs 26.1.50 |
Emilio G. Cota <address@hidden> 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 <address@hidden>
Reviewed-by: Alex Bennée <address@hidden>
> ---
> 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
- [Qemu-devel] [RFC v2 0/5] Dynamic TLB sizing, Emilio G. Cota, 2018/10/08
- [Qemu-devel] [RFC v2 4/5] cputlb: track TLB use rate, Emilio G. Cota, 2018/10/08
- [Qemu-devel] [RFC v2 2/5] (XXX) cputlb: introduce indirection for TLB size, Emilio G. Cota, 2018/10/08
- [Qemu-devel] [RFC v2 5/5] cputlb: dynamically resize TLBs based on use rate, Emilio G. Cota, 2018/10/08
- [Qemu-devel] [RFC v2 1/5] tcg: Add tlb_index and tlb_entry helpers, Emilio G. Cota, 2018/10/08
- [Qemu-devel] [RFC v2 3/5] cputlb: do not evict empty entries to the vtlb, Emilio G. Cota, 2018/10/08
- Re: [Qemu-devel] [RFC v2 0/5] Dynamic TLB sizing, Alex Bennée, 2018/10/09