Messages in this thread | | | From | Nadav Amit <> | Subject | Re: [PATCH] x86/mm/tlb: Remove flush_tlb_info from the stack | Date | Tue, 23 Apr 2019 16:56:54 +0000 |
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> On Apr 23, 2019, at 9:50 AM, Andy Lutomirski <luto@kernel.org> wrote: > > On Tue, Apr 23, 2019 at 12:12 AM Nadav Amit <namit@vmware.com> wrote: >> Remove flush_tlb_info variables from the stack. This allows to align >> flush_tlb_info to cache-line and avoid potentially unnecessary cache >> line movements. It also allows to have a fixed virtual-to-physical >> translation of the variables, which reduces TLB misses. >> >> Use per-CPU struct for flush_tlb_mm_range() and >> flush_tlb_kernel_range(). Add debug assertions to ensure there are >> no nested TLB flushes that might overwrite the per-CPU data. For >> arch_tlbbatch_flush(), use a const struct. >> >> Results when running a microbenchmarks that performs 10^6 MADV_DONTEED >> operations and touching a page, in which 3 additional threads run a >> busy-wait loop (5 runs): > > Can you add a memset(,,,. 0, sizeof(struct flush_tlb_info)) everywhere > you grab it? Or, even better, perhaps do something like: > > static inline struct flush_tlb_info *get_flush_tlb_info(void) > { > /* check reentrancy, make sure that we use smp_processor_id() or > otherwise assert that we're bound to a single CPU. */ > struct flush_tlb_info *ptr = this_cpu_ptr(...); > memset(ptr, 0, sizeof(*ptr)); > return ptr; > } > > static inline void put_flush_tlb_info(void) > { > /* finish checking reentrancy. */ > }
I’ll check if the compiler is smart enough to avoid redundant assignments, and if it is not, I’ll just give all the struct arguments to get_flush_tlb_info() instead of memset() if you don’t mind.
I also want to give a try for parallelizing the remote and local invocations, which really annoys me every time I look at the code. Please let me know if there is any “big reason” that I am missing for it not to be done before. I just hope all the paravirt stuff will not make it too ugly.
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