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| author | Anton Ivanov <anton.ivanov@cambridgegreys.com> | 2018-12-07 09:05:53 +0000 |
|---|---|---|
| committer | Richard Weinberger <richard@nod.at> | 2018-12-27 22:48:34 +0100 |
| commit | 742f3c8193a3cb3e444887211214ef0721e3ef8d (patch) | |
| tree | c74eb64a5d8b02cca48b7b5ab7e97b415fc957bf /arch/um | |
| parent | 8892d8545f2d0342b9c550defbfb165db237044b (diff) | |
| download | linux-0-day-742f3c8193a3cb3e444887211214ef0721e3ef8d.tar.gz linux-0-day-742f3c8193a3cb3e444887211214ef0721e3ef8d.tar.xz | |
um: Optimize Flush TLB for force/fork case
When UML handles a fork the page tables need to be brought up
to date. That was done using brute force - full tlb flush.
This is actually unnecessary, because the mapped-in mappings are
all correct and the only mappings which need to be updated
after a flush are any unmaps (so that paging works) as well as
any pending protection changes.
This optimization squeezes out up to 3% from a full kernel rebuild
time under memory pressure.
Signed-off-by: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Diffstat (limited to 'arch/um')
| -rw-r--r-- | arch/um/kernel/tlb.c | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/arch/um/kernel/tlb.c b/arch/um/kernel/tlb.c index 9ca902df243a3..8347161c2ae0f 100644 --- a/arch/um/kernel/tlb.c +++ b/arch/um/kernel/tlb.c @@ -242,10 +242,11 @@ static inline int update_pte_range(pmd_t *pmd, unsigned long addr, prot = ((r ? UM_PROT_READ : 0) | (w ? UM_PROT_WRITE : 0) | (x ? UM_PROT_EXEC : 0)); if (hvc->force || pte_newpage(*pte)) { - if (pte_present(*pte)) - ret = add_mmap(addr, pte_val(*pte) & PAGE_MASK, - PAGE_SIZE, prot, hvc); - else + if (pte_present(*pte)) { + if (pte_newpage(*pte)) + ret = add_mmap(addr, pte_val(*pte) & PAGE_MASK, + PAGE_SIZE, prot, hvc); + } else ret = add_munmap(addr, PAGE_SIZE, hvc); } else if (pte_newprot(*pte)) ret = add_mprotect(addr, PAGE_SIZE, prot, hvc); |