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Signed-off-by: Andrew Xia <axia@fb.com>
Co-authored-by: Andrew Xia <axia@fb.com>

Signed-off-by: Nick Hill <nhill@redhat.com>

Introduces three new Prometheus histograms for fine-grained observability of KV cache residency behavior:

vllm:kv_block_lifetime_seconds — total lifetime from allocation to free
vllm:kv_block_idle_before_evict_seconds — idle duration before eviction
vllm:kv_block_reuse_gap_seconds — time between consecutive reuses of the same block

These metrics help operators analyze KV cache efficiency, reuse patterns, and eviction timing beyond simple utilization rates.

Implementation uses monotonic timestamps for accuracy, 1% sampling for minimal overhead (~48 bytes/block), and is fully thread-safe with zero runtime cost when disabled.

Two new runtime flags are introduced:

--kv-cache-metrics – enable KV cache residency metrics
--kv-cache-metrics-sample – control sampling ratio (default: 0.01)
Signed-off-by: Shivam <shivamprasad91@gmail.com>

Signed-off-by: knlnguyen1802 <knlnguyen1802@gmail.com>
Co-authored-by: Chenguang Zheng <645327136@qq.com>
Co-authored-by: Cyrus Leung <cyrus.tl.leung@gmail.com>
Co-authored-by: Cyrus Leung <tlleungac@connect.ust.hk>

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Signed-off-by: sangbumlikeagod <oironese@naver.com>
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Co-authored-by: Cyrus Leung <tlleungac@connect.ust.hk>

Signed-off-by: DarkLight1337 <tlleungac@connect.ust.hk>

Signed-off-by: Daniel Salib <danielsalib@meta.com>
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Signed-off-by: wang.yuqi <yuqi.wang@daocloud.io>

Signed-off-by: Huamin Li <3ericli@gmail.com>

Signed-off-by: DarkLight1337 <tlleungac@connect.ust.hk>

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Signed-off-by: vensen <vensenmu@gmail.com>
Co-authored-by: TJian <tunjian.tan@embeddedllm.com>

Signed-off-by: Xin Yang <xyangx@amazon.com>
Signed-off-by: Xin Yang <105740670+xyang16@users.noreply.github.com>
Co-authored-by: Jee Jee Li <pandaleefree@gmail.com>

Signed-off-by: Jee Jee Li <pandaleefree@gmail.com>

Signed-off-by: Jinzhen Lin <jinzhen.ljz@antgroup.com>
Signed-off-by: Michael Goin <mgoin64@gmail.com>
Signed-off-by: Jinzhen Lin <linjinzhen@hotmail.com>
Co-authored-by: Michael Goin <mgoin64@gmail.com>
Co-authored-by: Michael Goin <mgoin@redhat.com>

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Signed-off-by: DarkLight1337 <tlleungac@connect.ust.hk>

Signed-off-by: Jee Jee Li <pandaleefree@gmail.com>
Co-authored-by: Cyrus Leung <tlleungac@connect.ust.hk>

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Co-authored-by: Luka Govedič <ProExpertProg@users.noreply.github.com>

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Signed-off-by: Tsukasa OI <floss_llm@irq.a4lg.com>

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Signed-off-by: Andreas Karatzas <akaratza@amd.com>

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Co-authored-by: Roger Wang <hey@rogerw.io>

Signed-off-by: Huamin Li <3ericli@gmail.com>

Signed-off-by: DarkLight1337 <tlleungac@connect.ust.hk>
Signed-off-by: Cyrus Leung <cyrus.tl.leung@gmail.com>
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Signed-off-by: Benjamin Chislett <bchislett@nvidia.com>
Signed-off-by: Benjamin Chislett <chislett.ben@gmail.com>

Signed-off-by: Yanan Cao <gmagogsfm@gmail.com>
Co-authored-by: Claude <noreply@anthropic.com>

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Signed-off-by: DarkLight1337 <tlleungac@connect.ust.hk>

Signed-off-by: Isotr0py <mozf@mail2.sysu.edu.cn>

Signed-off-by: Nick Hill <nhill@redhat.com>

Signed-off-by: DarkLight1337 <tlleungac@connect.ust.hk>