linux-5.15/compaction_suitable() の履歴(No.1)

• 履歴一覧
• 差分 を表示
• 現在との差分 を表示
• ソース を表示
• linux-5.15/compaction_suitable() へ行く。
  • 1 (2025-09-11 (木) 11:07:39)

参照元†

• linux-5.15/kcompactd_do_work()

説明†

• パス: [[linux-5.15/]]

• FIXME: これは何？
  • 説明

引数†

返り値†

参考†

実装†

/*
 * compaction_suitable: Is this suitable to run compaction on this zone now?
 * Returns
 *   COMPACT_SKIPPED  - If there are too few free pages for compaction
 *   COMPACT_SUCCESS  - If the allocation would succeed without compaction
 *   COMPACT_CONTINUE - If compaction should run now
 */
enum compact_result compaction_suitable(struct zone *zone, int order,
					unsigned int alloc_flags,
					int highest_zoneidx)
{
	enum compact_result ret;
	int fragindex;

	ret = __compaction_suitable(zone, order, alloc_flags, highest_zoneidx,
				    zone_page_state(zone, NR_FREE_PAGES));

• • linux-5.15/__compaction_suitable()
  • linux-5.15/zone_page_state()

	/*
	 * fragmentation index determines if allocation failures are due to
	 * low memory or external fragmentation
	 *
	 * index of -1000 would imply allocations might succeed depending on
	 * watermarks, but we already failed the high-order watermark check
	 * index towards 0 implies failure is due to lack of memory
	 * index towards 1000 implies failure is due to fragmentation
	 *
	 * Only compact if a failure would be due to fragmentation. Also
	 * ignore fragindex for non-costly orders where the alternative to
	 * a successful reclaim/compaction is OOM. Fragindex and the
	 * vm.extfrag_threshold sysctl is meant as a heuristic to prevent
	 * excessive compaction for costly orders, but it should not be at the
	 * expense of system stability.
	 */
	if (ret == COMPACT_CONTINUE && (order > PAGE_ALLOC_COSTLY_ORDER)) {
		fragindex = fragmentation_index(zone, order);
		if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
			ret = COMPACT_NOT_SUITABLE_ZONE;
	}

• • linux-5.15/fragmentation_index()

	trace_mm_compaction_suitable(zone, order, ret);
	if (ret == COMPACT_NOT_SUITABLE_ZONE)
		ret = COMPACT_SKIPPED;

	return ret;
}

• • linux-5.15/trace_mm_compaction_suitable()

コメント†