linux-kernel - Re: upcoming kerneloops.org item: get_page_from

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Date:	Wed, 24 Jun 2009 12:16:20 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	penberg@...helsinki.fi, arjan@...radead.org,
	linux-kernel@...r.kernel.org, cl@...ux-foundation.org,
	npiggin@...e.de
Subject: Re: upcoming kerneloops.org item: get_page_from_freelist



On Wed, 24 Jun 2009, Andrew Morton wrote:
>
> My original patch was motiviated by the horror at discovering that
> we're using this thing (which was _never_ supposed to have new users)
> for order>0 allocations.  We've gone backwards.

Don't be silly.

We've always depended on order-1 allocations working. 

You're just totally misguided in your arguments, and you are 
FUNDAMENTALLY WRONG. Your argument is shit, BECAUSE IT IS NOT TRUE!

Lookie here. This is 2.6.0:mm/page_alloc.c:

        do_retry = 0;
        if (!(gfp_mask & __GFP_NORETRY)) {
                if ((order <= 3) || (gfp_mask & __GFP_REPEAT))
                        do_retry = 1;
                if (gfp_mask & __GFP_NOFAIL)
                        do_retry = 1;
        }
        if (do_retry) {
                blk_congestion_wait(WRITE, HZ/50);
                goto rebalance;
        }

Read that. Read if five times. Read it until you understand what it does.

			Linus

PS. Here's a clue: Look at that 'order <= 3' thing. Think about what 
happens EVEN IF __NOFAIL) was not even set!
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