linux-kernel - Re: [PATCH] [0/13] General DMA zone rework

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Date:	Tue, 11 Mar 2008 14:26:24 -0300
From:	"Luiz Fernando N. Capitulino" <lcapitulino@...driva.com.br>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] [0/13] General DMA zone rework

Em Mon, 10 Mar 2008 19:08:43 +0100
Andi Kleen <andi@...stfloor.org> escreveu:

| > you have or only the subset you posted?
| 
| Best you test all together. The subsets are independent
| (as in kernel should work with any subset of them), but 
| they all clean up DMA memory related issues.

 Ok, now it works with the test case fixed:

"""
testing mask alloc upto 24 bits
verify & free
mask fffff
mask 1fffff
mask 3fffff
mask 7fffff
mask ffffff
done
"""

 Do you remember the BUG_ON() I was getting because of the
sound card driver [1] ?

 It seems to me that the problem is that it's setting
__GFP_COMP. The following patch fixes it for me:

"""
Index: linux-2.6.24/sound/core/memalloc.c
===================================================================
--- linux-2.6.24.orig/sound/core/memalloc.c
+++ linux-2.6.24/sound/core/memalloc.c
@@ -218,7 +218,6 @@ static void *snd_malloc_dev_pages(struct
 	snd_assert(dma != NULL, return NULL);
 	pg = get_order(size);
 	gfp_flags = GFP_KERNEL
-		| __GFP_COMP	/* compound page lets parts be mapped */
 		| __GFP_NORETRY /* don't trigger OOM-killer */
 		| __GFP_NOWARN; /* no stack trace print - this call is non-critical */
 	res = dma_alloc_coherent(dev, PAGE_SIZE << pg, dma, gfp_flags);
"""

 Also, I think you forgot to protect the __free_pages_mask()
call with "#ifdef CONFIG_MASK_ALLOC" in patch mask-compat.

 Question: let's say that the devices I have consumes only
5MB of the whole reserved pool (16MB), of course that it's
ok to reduce the pool to 5MB, right?

 I have more machines to test this stuff...

[1] http://users.mandriva.com.br/~lcapitulino/tmp/minicom.cap

-- 
Luiz Fernando N. Capitulino
--
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