ee61b11a9e
d164a04342node: smooth oversized `-dbcache` warnings (Lőrinc) Pull request description: **Problem:** The oversized `-dbcache` warning threshold has a sharp formula cliff when detected RAM crosses the cutoff used by the warning logic. This was reported during review of [#34641](https://github.com/bitcoin/bitcoin/pull/34641#discussion_r2900769756), where an earlier version could jump from the auto default at `4095 MiB` RAM to `75%` of RAM at `4096 MiB`. That made `1 MiB` of extra detected RAM raise the warning threshold from about `511 MiB` to `3072 MiB`. The surviving warning-only code has the same shape at a different boundary. Below `2 GiB` RAM the cap is `DEFAULT_DB_CACHE` (`450 MiB`), but at `2 GiB` it switches to `75%` of total RAM, so a tiny increase in detected RAM can suddenly raise the warning threshold from `450 MiB` to about `1536 MiB`. <img width="1484" height="881" alt="Image" src="https://github.com/user-attachments/assets/b51d5d24-31b8-4a2a-8f70-e7536481f855" /> **Fix:** Base the warning on a reserved non-dbcache memory budget instead: ```math \text{warn if } \mathit{dbcache} > \max\left(\mathit{DEFAULT\_DB\_CACHE}, 0.75 \cdot \max(\text{total RAM} - \mathit{DBCACHE\_WARNING\_RESERVED\_RAM}, 0)\right) ``` `DBCACHE_WARNING_RESERVED_RAM` is `2 GiB`, so the fixed `DEFAULT_DB_CACHE` cap remains the floor below that reserve and the warning threshold grows monotonically above it. This keeps the warning conservative around low-memory boundaries and avoids treating a boundary-crossing `1 MiB` RAM difference as a reason to allow a much larger explicit `-dbcache`. **Quick reference:** | System RAM | Previous warning cap | New warning cap | | ---------- | -------------------- | --------------- | | 1 GiB | 450 MiB | 450 MiB | | 2 GiB | 1536 MiB | 450 MiB | | 3 GiB | 2304 MiB | 768 MiB | | 4 GiB | 3072 MiB | 1536 MiB | | 8 GiB | 6144 MiB | 4608 MiB | | 16 GiB | 12288 MiB | 10752 MiB | | 32 GiB | 24576 MiB | 23040 MiB | On 32-bit builds, effective `-dbcache` values are still capped to `1024 MiB` before the warning check, so thresholds above that cap are not reachable there. ACKs for top commit: optout21: reACKd164a04342sedited: Re-ACKd164a04342w0xlt: reACKd164a04342Tree-SHA512: deb81f0e192261f01dda6f1575a7b2e147f1e07e813d0833c7aeaf6a3fbd7594c0145ec1c98ded74efee9005108d229942949279c9458cbec4046913387db845
Bitcoin Core integration/staging tree
For an immediately usable, binary version of the Bitcoin Core software, see https://bitcoincore.org/en/download/.
What is Bitcoin Core?
Bitcoin Core connects to the Bitcoin peer-to-peer network to download and fully validate blocks and transactions. It also includes a wallet and graphical user interface, which can be optionally built.
Further information about Bitcoin Core is available in the doc folder.
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