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[esp32] IRAM_ATTR on dispatch, document cold path

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Put IRAM_ATTR back on esp_log_format (tiny ~43 byte dispatch function)
to match esp_log_va's IRAM placement and avoid cache miss. Leave the
512-byte formatting function in flash — it's cold on 99.9% of builds
(only runs during early boot and at DEBUG framework log level).
This commit is contained in:
J. Nick Koston
2026-03-13 18:18:19 -10:00
parent 4fbd0f1595
commit fd3aa3f2ef
1 changed files with 6 additions and 4 deletions
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10
esphome/core/log.cpp
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@@ -102,6 +102,8 @@ int HOT esp_idf_log_vprintf_(const char *format, va_list args) { // NOLINT
// locks crash on USB JTAG devices).
// Formats in ESPHome style with ANSI colors into a 512-byte stack buffer,
// then outputs atomically via esp_rom_printf.
// This path is cold on 99.9% of builds — it only runs during early boot
// and at DEBUG framework log level (default is ERROR).
static void __attribute__((noinline)) esp_log_format_direct_(esp_log_msg_t *message) {
// ESP-IDF levels: NONE=0 ERROR=1 WARN=2 INFO=3 DEBUG=4 VERBOSE=5
// Color digits: E=1(red) W=3(yellow) I=2(green) D=6(cyan) V=7(gray)
@@ -133,10 +135,10 @@ static void __attribute__((noinline)) esp_log_format_direct_(esp_log_msg_t *mess
extern "C" {
// Override esp_log_format from liblog.a to prevent V2's 3-call vprintf
// fragmentation. No IRAM_ATTR needed — the only case where flash is
// inaccessible (ISR with cache disabled) would crash anyway because the
// caller's format string and tag are also in flash.
void esp_log_format(esp_log_msg_t *message) {
// fragmentation. IRAM_ATTR to match esp_log_va's IRAM placement and avoid
// an IRAM→flash cache miss on every ESP-IDF log call. This function is
// tiny (~43 bytes) so the IRAM cost is negligible.
void IRAM_ATTR esp_log_format(esp_log_msg_t *message) {
extern vprintf_like_t esp_log_vprint_func;
extern int vprintf(const char *, __gnuc_va_list); // NOLINT
if (esp_log_vprint_func == &vprintf || message->config.opts.constrained_env) [[unlikely]] {