intel_pt_find_overlap(9)

💅 intel_pt_find_overlap — a Kernel API Manual moment, bestie

okay so this one is from the Kernel API Manual (yes, the Kernel API Manual, we're fancy now 💅) and it's about figuring out where the actually-new part of your trace data starts. let's get into it 🎀

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✨ NAME ✨

intel_pt_find_overlap — determine start of non-overlapped trace data.

like, literally its whole job is spotting where the overlap ends and the fresh data begins. icon behaviour honestly 👑

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🦋 SYNOPSIS 🦋

unsigned char * intel_pt_find_overlap (unsigned char *buf_a , size_t
len_a , unsigned char *buf_b , size_t len_b , bool have_tsc , bool
*consecutive , bool ooo_tsc );

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💖 ARGUMENTS 💖

• buf_a — first buffer. that's the one you already had.
• len_a — size of first buffer. how much buf_a we're working with.
• buf_b — second buffer. the new one coming in.
• len_b — size of second buffer. the size of buf_b, no cap.
• have_tsc — can use TSC packets to detect overlap. so like, are we allowed to read the TSC packets to sniff out the overlap or not 🕵️
• consecutive — returns true if there is data in buf_b that is consecutive to buf_a. it's an out-param, so it tells you the answer 💌
• ooo_tsc — out-of-order TSC due to VM TSC offset / scaling. yes that's a real thing that happens in VMs, and yes it matters here 🌸

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🌈 DESCRIPTION 🌈

okay so when trace samples or snapshots are recorded there is the possibility that the data overlaps. that's the whole situation. two buffers, potential double-dipping, we gotta sort it out.

note that, for the purposes of decoding, data is only useful if it begins with a PSB packet. like, fr fr, that's the rule. no PSB at the start = not useful to the decoder. periodt.

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🔥 RETURN 🔥

it hands you back a pointer into buf_b from where non-overlapped data starts. ✨

or, if there's literally no non-overlapped data at all, you get buf_b + len_b. literally the end of the buffer, the "nothing for you here" pointer 😭

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🫶 SEE ALSO 🫶

• Kernel file ./tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
• intel_pt_next_psb(9)
• intel_pt_step_psb(9)
• intel_pt_last_psb(9)
• intel_pt_next_tsc(9)
• intel_pt_tsc_cmp(9)
• adj_for_padding(9)
• intel_pt_find_overlap_tsc(9)
• struct fast_forward_data(9)
• intel_pt_ff_cb(9)
• intel_pt_fast_forward(9)

go read those next bestie, they're all part of the same squad 💜

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k that's the whole page!! source is ./tools/perf/util/intel-pt-dec... and it's dated October 2026, so mark your calendar 🎀 thanks for reading my lil manual era, mwah 💋✨