Commit 6d4831c2 authored Apr 27, 2011 by Andrew Morton Committed by Linus Torvalds Apr 28, 2011

vfs: avoid large kmalloc()s for the fdtable



Azurit reports large increases in system time after 2.6.36 when running
Apache.  It was bisected down to a892e2d7 ("vfs: use kmalloc()
to allocate fdmem if possible").

That patch caused the vfs to use kmalloc() for very large allocations and
this is causing excessive work (and presumably excessive reclaim) within
the page allocator.

Fix it by falling back to vmalloc() earlier - when the allocation attempt
would have been considered "costly" by reclaim.

Reported-by: azurIt <azurit@pobox.sk>
Tested-by: azurIt <azurit@pobox.sk>
Acked-by: Changli Gao <xiaosuo@gmail.com>
Cc: Americo Wang <xiyou.wangcong@gmail.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent e8dad694

fs/file.c

+11 −7

Original line number	Diff line number	Diff line
		@@ -9,6 +9,7 @@
		#include <linux/module.h>
		#include <linux/fs.h>
		#include <linux/mm.h>
		#include <linux/mmzone.h>
		#include <linux/time.h>
		#include <linux/sched.h>
		#include <linux/slab.h>
		@@ -39,14 +40,17 @@ int sysctl_nr_open_max = 1024 * 1024; /* raised later */
		*/
		static DEFINE_PER_CPU(struct fdtable_defer, fdtable_defer_list);

		static inline void *alloc_fdmem(unsigned int size)
		static void *alloc_fdmem(unsigned int size)
		{
		void *data;

		data = kmalloc(size, GFP_KERNEL\|__GFP_NOWARN);
		/*
		* Very large allocations can stress page reclaim, so fall back to
		* vmalloc() if the allocation size will be considered "large" by the VM.
		*/
		if (size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER)) {
		void *data = kmalloc(size, GFP_KERNEL\|__GFP_NOWARN);
		if (data != NULL)
		return data;

		}
		return vmalloc(size);
		}

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