linux-kernel - [patch 23/25] debugobjects: Double the per CPU slots

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Message-ID: <20241007164914.378676302@linutronix.de>
Date: Mon,  7 Oct 2024 18:50:19 +0200 (CEST)
From: Thomas Gleixner <tglx@...utronix.de>
To: LKML <linux-kernel@...r.kernel.org>
Cc: Zhen Lei <thunder.leizhen@...wei.com>,
 Waiman Long <longman@...hat.com>
Subject: [patch 23/25] debugobjects: Double the per CPU slots

In situations where objects are rapidly allocated from the pool and handed
back, the size of the per CPU pool turns out to be too small.

Double the size of the per CPU pool.

This reduces the kmem cache allocation and free operations during a kernel compile:

     	     alloc    	    free
Baseline:    380k           330k
Double size: 295k	    245k

Especially the reduction of allocations is important because that happens
in the hot path when objects are initialized.

The maximum increase in per CPU pool memory consumption is about 2.5K per
online CPU, which is acceptable.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 lib/debugobjects.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/lib/debugobjects.c
+++ b/lib/debugobjects.c
@@ -28,7 +28,7 @@
 #define ODEBUG_POOL_SIZE	(64 * ODEBUG_BATCH_SIZE)
 #define ODEBUG_POOL_MIN_LEVEL	(ODEBUG_POOL_SIZE / 4)

-#define ODEBUG_POOL_PERCPU_SIZE	(4 * ODEBUG_BATCH_SIZE)
+#define ODEBUG_POOL_PERCPU_SIZE	(8 * ODEBUG_BATCH_SIZE)

 #define ODEBUG_CHUNK_SHIFT	PAGE_SHIFT
 #define ODEBUG_CHUNK_SIZE	(1 << ODEBUG_CHUNK_SHIFT)