linux-kernel - [PATCH] Try to avoid a pessimistic vmalloc() recursion

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Message-Id: <200610091647.55184.dada1@cosmosbay.com>
Date:	Mon, 9 Oct 2006 16:47:55 +0200
From:	Eric Dumazet <dada1@...mosbay.com>
To:	Andrew Morton <akpm@...l.org>
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] Try to avoid a pessimistic vmalloc() recursion

__vmalloc_area_node() is a litle bit pessimist when allocating space for 
storing struct page pointers.

When allocating more than 4 MB on ia32, or 2 MB on x86_64,  
__vmalloc_area_node() has to allocate more than PAGE_SIZE bytes to store 
pointers to  page structs. This means that two TLB translations are needed to 
access data.

This patch tries a kmalloc() call, then only if this first attempt failed, a 
vmalloc() is performed. (Later, at vfree() time we chose kfree() or vfree() 
with a test on flags & VM_VPAGES : no change is needed) 

Most of the time, the first kmalloc() should be OK, so we reduce TLB usage.

Signed-off-by: Eric Dumazet <dada1@...mosbay.com>

View attachment "vmalloc.patch" of type "text/plain" (703 bytes)