evlist__mmap_ex(9)

✨ evlist__mmap_ex(9) ✨

okay so bestie, we're in the Kernel API Manual today and this one is literally the mmap machine 💅 it lives in evlist__mmap_ex(9) and it's all about creating mmaps so you can receive events. no cap. 🎀

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🌸 NAME 🌸

evlist__mmap_ex — Create mmaps to receive events. and yes that's the whole name, she's concise, she's iconic 👑

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🦋 SYNOPSIS 🦋

int evlist__mmap_ex (struct evlist *evlist , unsigned int pages ,
       unsigned int auxtrace_pages , bool auxtrace_overwrite , int nr_cblocks ,
       int affinity , int flush , int comp_level );

like, look at her go. eight whole parameters. main character energy fr fr 😭

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💖 ARGUMENTS 💖

• evlist — the list of events. that's the vibe. that's the guest list for the party 🎉
• pages — the map length, measured in pages. yes pages. not bytes. do not come for me 🫶
• auxtrace_pages — honestly? -- undescribed --. the docs said nothing. i'm not gonna make something up, that would be lying to you and we don't do that 💀
• auxtrace_overwrite — also -- undescribed -- 🙈 so mysterious. so unbothered. so undocumented ✨
• nr_cblocks — -- undescribed -- 😭 the manpage truly said "no thoughts head empty" on this one
• affinity — -- undescribed -- 🦋 (sensing a pattern? yeah. same.)
• flush — -- undescribed -- 💀
• comp_level — -- undescribed -- 🍓

ngl bestie, seven of the eight arguments are literally marked -- undescribed -- in the original. that's not me being lazy, that's just the canon. i refuse to invent behavior, that's not the move 🧚

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🧚 DESCRIPTION 🧚

so here's the actual tea ☕

If overwrite is false, the user needs to signal event consumption using perf_mmap__write_tail. good news though — using evlist__mmap_read does this automatically, so you don't have to hand-write the tail yourself 😌 slay.

Similarly (and yes, "similarly", they said it first), if auxtrace_overwrite is false, the user needs to signal data consumption using auxtrace_mmap__write_tail. same energy, different mmap 💅

⚠️ lowkey important: those false cases mean you have to do the signaling. nobody's coming to save you. the automatic path is only the evlist__mmap_read one. ok that's the whole warning, carry on 🫶

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🔥 RETURN 🔥

• 0 on success 🎉 (the dream)
• a negative error code otherwise 😭 (the villain arc)

periodt.

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🌈 SEE ALSO 🌈

go read these next, they're the friend group 👑

• Kernel file ./tools/perf/util/evlist.c — the source, the origin story, the mothership
• evlist__set_id_pos(9)
• struct event_enable_time(9)
• struct event_enable_timer(9)
• evlist__warn_user_requested_cpus(9)

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💜 cute sign-off 💜

this page came to you straight from ./tools/perf/util, dated October 2026 — that's the source/version and the date, all folded up into one little goodbye 🎀

okay bye bestie, go mmap something responsibly 💖✨🦋