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in_tail: fix file_cache_advise causing high disk IOPS #11660

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in_tail: fix file_cache_advise causing high disk IOPS #11660

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18 changes: 9 additions & 9 deletions plugins/in_tail/tail_file.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1698,15 +1698,6 @@ int flb_tail_file_chunk(struct flb_tail_file *file)
file_buffer_capacity = (file->buf_size - file->buf_len) - 1;
}

#ifdef __linux__
if (ctx->file_cache_advise) {
if (posix_fadvise(file->fd, 0, 0, POSIX_FADV_DONTNEED) == -1) {
flb_errno();
flb_plg_error(ctx->ins, "error during posix_fadvise");
}
}
#endif

read_size = file_buffer_capacity;

if (file->decompression_context != NULL) {
Expand Down Expand Up @@ -1822,6 +1813,15 @@ int flb_tail_file_chunk(struct flb_tail_file *file)
file->buf_len -= processed_bytes;
file->buf_data[file->buf_len] = '\0';

#ifdef __linux__
/* Evict only the already-processed byte range from the page cache
* so that kernel readahead for upcoming reads is preserved. */
if (ctx->file_cache_advise && file->stream_offset > 0) {
posix_fadvise(file->fd, 0, file->stream_offset,
POSIX_FADV_DONTNEED);
}
#endif

#ifdef FLB_HAVE_SQLDB
if (file->config->db) {
flb_tail_db_file_offset(file, file->config);
Expand Down
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