linux/fs/cachefiles
Mel Gorman 453f85d43f mm: remove __GFP_COLD
As the page free path makes no distinction between cache hot and cold
pages, there is no real useful ordering of pages in the free list that
allocation requests can take advantage of.  Juding from the users of
__GFP_COLD, it is likely that a number of them are the result of copying
other sites instead of actually measuring the impact.  Remove the
__GFP_COLD parameter which simplifies a number of paths in the page
allocator.

This is potentially controversial but bear in mind that the size of the
per-cpu pagelists versus modern cache sizes means that the whole per-cpu
list can often fit in the L3 cache.  Hence, there is only a potential
benefit for microbenchmarks that alloc/free pages in a tight loop.  It's
even worse when THP is taken into account which has little or no chance
of getting a cache-hot page as the per-cpu list is bypassed and the
zeroing of multiple pages will thrash the cache anyway.

The truncate microbenchmarks are not shown as this patch affects the
allocation path and not the free path.  A page fault microbenchmark was
tested but it showed no sigificant difference which is not surprising
given that the __GFP_COLD branches are a miniscule percentage of the
fault path.

Link: http://lkml.kernel.org/r/20171018075952.10627-9-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-11-15 18:21:06 -08:00
..
Kconfig
Makefile License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
bind.c VFS: Convert sb->s_flags & MS_RDONLY to sb_rdonly(sb) 2017-07-17 08:45:34 +01:00
daemon.c CacheFiles: Provide read-and-reset release counters for cachefilesd 2016-02-01 12:30:10 -05:00
interface.c cachefiles: Fix attempt to read i_blocks after deleting file [ver #2] 2016-09-27 18:31:29 -04:00
internal.h sched/wait: Split out the wait_bit*() APIs from <linux/wait.h> into <linux/wait_bit.h> 2017-06-20 12:19:09 +02:00
key.c
main.c
namei.c sched/wait: Rename wait_queue_t => wait_queue_entry_t 2017-06-20 12:18:27 +02:00
proc.c drop redundant ->owner initializations 2016-05-29 19:08:00 -04:00
rdwr.c mm: remove __GFP_COLD 2017-11-15 18:21:06 -08:00
security.c VFS: fs/cachefiles: d_backing_inode() annotations 2015-04-15 15:06:59 -04:00
xattr.c VFS: fs/cachefiles: d_backing_inode() annotations 2015-04-15 15:06:59 -04:00