Re: [RFC] propagate gfp_t to page table alloc functions
From: Nick Piggin <npiggin@gmail.com>
Date: 2012-05-01 07:20:54
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On 25 April 2012 07:30, Andrew Morton [off-list ref] wrote:
On Tue, 24 Apr 2012 17:48:29 +1000 Nick Piggin [off-list ref] wrote:quoted
quoted
Hmm, there are several places to use GFP_NOIO and GFP_NOFS even, GFP_ATOMIC. I believe it's not trivial now.They're all buggy then. Unfortunately not through any real fault of their own.There are gruesome problems in block/blk-throttle.c (thread "mempool, percpu, blkcg: fix percpu stat allocation and remove stats_lock"). It wants to do an alloc_percpu()->vmalloc() from the IO submission path, under GFP_NOIO.
Yeah, that sucks. CFQ has something similar. Should just allocate it up front when creating a throttled group. Allocate and init when it first gets used schemes are usually pretty problematic. Is it *really* warranted to do it lazily like this?
Changing vmalloc() to take a gfp_t does make lots of sense, although I worry a bit about making vmalloc() easier to use! I do wonder whether the whole scheme of explicitly passing a gfp_t was a mistake and that the allocation context should be part of the task context. ie: pass the allocation mode via *current. As a handy side-effect that would probably save quite some code where functions are receiving a gfp_t arg then simply passing it on to the next callee.
Both paragraphs make a lot of sense. Conceptually. :) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>