Re: [PATCH v9 tip 8/9] samples: bpf: IO latency analysis (iosnoop/heatmap)

On 3/23/15 12:40 AM, Ingo Molnar wrote: * Alexei Starovoitov wrote: BPF C program attaches to blk_mq_start_request/blk_update_request kprobe events to calculate IO latency. ... +/* kprobe is NOT a stable ABI + * This bpf+kprobe example can stop working any time. + */ +SEC("kprobe/blk_mq

Re: [PATCH v9 tip 8/9] samples: bpf: IO latency analysis (iosnoop/heatmap)

* Alexei Starovoitov wrote: > BPF C program attaches to blk_mq_start_request/blk_update_request kprobe > events > to calculate IO latency. ... > +/* kprobe is NOT a stable ABI > + * This bpf+kprobe example can stop working any time. > + */ > +SEC("kprobe/blk_mq_start_request") > +int bpf_pro

[PATCH v9 tip 8/9] samples: bpf: IO latency analysis (iosnoop/heatmap)

BPF C program attaches to blk_mq_start_request/blk_update_request kprobe events to calculate IO latency. For every completed block IO event it computes the time delta in nsec and records in a histogram map: map[log10(delta)*10]++ User space reads this histogram map every 2 seconds and prints it as