From 3cea94bbc97180dd2de78993982645b11405b3b2 Mon Sep 17 00:00:00 2001 From: "Emilio G. Cota" Date: Wed, 16 Jan 2019 12:01:12 -0500 Subject: cputlb: do not evict empty entries to the vtlb MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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. Tested-by: Alex Bennée Reviewed-by: Alex Bennée Reviewed-by: Richard Henderson Signed-off-by: Emilio G. Cota Message-Id: <20190116170114.26802-2-cota@braap.org> Signed-off-by: Richard Henderson --- accel/tcg/cputlb.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) (limited to 'accel/tcg/cputlb.c') diff --git a/accel/tcg/cputlb.c b/accel/tcg/cputlb.c index af6bd8ccf9..10f1150c62 100644 --- a/accel/tcg/cputlb.c +++ b/accel/tcg/cputlb.c @@ -224,6 +224,15 @@ static inline bool tlb_hit_page_anyprot(CPUTLBEntry *tlb_entry, tlb_hit_page(tlb_entry->addr_code, page); } +/** + * 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; +} + /* Called with tlb_c.lock held */ static inline void tlb_flush_entry_locked(CPUTLBEntry *tlb_entry, target_ulong page) @@ -591,7 +600,7 @@ 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]; -- cgit v1.2.3