STRUCT PT_BUFFER(9)

💖 struct pt_buffer(9) — Kernel API Manual, but make it a group chat 💖

okay bestie, so this is a page from the Kernel API Manual and it's literally about struct pt_buffer — which is the buffer configuration, and there's one buffer per task_struct or per cpu, depending on the perf event configuration. slay. two possible situations, one struct, very main character.

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✨ NAME ✨

struct pt_buffer — it's giving buffer configuration energy 🎀 one buffer per task_struct or cpu, depending on your perf event configuration. iykyk.

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🦋 SYNOPSIS 🦋

struct pt_buffer {
    struct list_head        tables;
    struct topa             *first, *last, *cur;
    unsigned int            cur_idx;
    size_t output_off;
    unsigned long           nr_pages;
    local_t data_size;
    local64_t head;
    bool snapshot;
    bool single;
    bool wrapped;
    long stop_pos, intr_pos;
    struct topa_entry       *stop_te, *intr_te;
    void **data_pages;
 };

like, that's the whole struct, no cap. copy it exactly if you need it, i'm not touching a single character 💅

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👑 Members 👑

okay so now we go through every single member, and no we are not skipping any, bestie. this is the whole list. periodt.

• tables — the list of ToPA tables chilling in this buffer 🫶
• first — shorthand for the first topa table, it's just a lil nickname
• last — shorthand for the last topa table, same vibe
• cur — the current topa table, the one we're literally on right now
• cur_idx — the index of the current output region within cur's table
• output_off — offset within the current output region, yes it's offset-ception
• nr_pages — buffer size, in pages (pages!! not bytes, bestie, watch out)
• data_size — a running total of how much data is in this buffer, like a little counter keeping track 🌸
• head — the logical write offset inside the buffer, this is where the writing vibes happen
• snapshot — true if this is for a snapshot/overwrite counter
• single — use Single Range Output instead of ToPA
• wrapped — buffer advance wrapped back to the first topa table, it did a little loop 🌀
• stop_pos — the STOP topa entry index
• intr_pos — the INT topa entry index
• stop_te — the STOP topa entry pointer
• intr_te — the INT topa entry pointer
• data_pages — array of pages from perf

💀 friendly reminder: stop_pos/intr_pos are the index versions and stop_te/intr_te are the pointer versions. don't mix them up, i'm begging 🙈

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🌈 SEE ALSO 🌈

go look at the kernel file ./arch/x86/events/intel/pt.h, and also these icons:

• struct pt_filter(9)
• struct pt_filters(9)
• struct pt(9)

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⭐ and that's the whole page, bestie. it lives under ./arch/x86/events/intel, dated October 2026, and you can find it chilling in struct pt_buffer(9) whenever you need it. ate and left no crumbs 💜🎀