linux/tools/perf
Michal Hocko 0ee931c4e3 mm: treewide: remove GFP_TEMPORARY allocation flag
GFP_TEMPORARY was introduced by commit e12ba74d8f ("Group short-lived
and reclaimable kernel allocations") along with __GFP_RECLAIMABLE.  It's
primary motivation was to allow users to tell that an allocation is
short lived and so the allocator can try to place such allocations close
together and prevent long term fragmentation.  As much as this sounds
like a reasonable semantic it becomes much less clear when to use the
highlevel GFP_TEMPORARY allocation flag.  How long is temporary? Can the
context holding that memory sleep? Can it take locks? It seems there is
no good answer for those questions.

The current implementation of GFP_TEMPORARY is basically GFP_KERNEL |
__GFP_RECLAIMABLE which in itself is tricky because basically none of
the existing caller provide a way to reclaim the allocated memory.  So
this is rather misleading and hard to evaluate for any benefits.

I have checked some random users and none of them has added the flag
with a specific justification.  I suspect most of them just copied from
other existing users and others just thought it might be a good idea to
use without any measuring.  This suggests that GFP_TEMPORARY just
motivates for cargo cult usage without any reasoning.

I believe that our gfp flags are quite complex already and especially
those with highlevel semantic should be clearly defined to prevent from
confusion and abuse.  Therefore I propose dropping GFP_TEMPORARY and
replace all existing users to simply use GFP_KERNEL.  Please note that
SLAB users with shrinkers will still get __GFP_RECLAIMABLE heuristic and
so they will be placed properly for memory fragmentation prevention.

I can see reasons we might want some gfp flag to reflect shorterm
allocations but I propose starting from a clear semantic definition and
only then add users with proper justification.

This was been brought up before LSF this year by Matthew [1] and it
turned out that GFP_TEMPORARY really doesn't have a clear semantic.  It
seems to be a heuristic without any measured advantage for most (if not
all) its current users.  The follow up discussion has revealed that
opinions on what might be temporary allocation differ a lot between
developers.  So rather than trying to tweak existing users into a
semantic which they haven't expected I propose to simply remove the flag
and start from scratch if we really need a semantic for short term
allocations.

[1] http://lkml.kernel.org/r/20170118054945.GD18349@bombadil.infradead.org

[akpm@linux-foundation.org: fix typo]
[akpm@linux-foundation.org: coding-style fixes]
[sfr@canb.auug.org.au: drm/i915: fix up]
  Link: http://lkml.kernel.org/r/20170816144703.378d4f4d@canb.auug.org.au
Link: http://lkml.kernel.org/r/20170728091904.14627-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: Mel Gorman <mgorman@suse.de>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Neil Brown <neilb@suse.de>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-09-13 18:53:16 -07:00
..
arch Char/Misc drivers for 4.14-rc1 2017-09-05 11:08:17 -07:00
bench perf tools: Use __maybe_unused consistently 2017-06-19 15:27:06 -03:00
Documentation perf script: Support physical address 2017-09-01 14:46:29 -03:00
jvmti perf jit: fix typo: "incalid" -> "invalid" 2017-06-27 11:55:06 -03:00
pmu-events perf vendor events powerpc: Remove duplicate events 2017-09-01 14:46:00 -03:00
python perf python: Add tracepoint example 2016-07-12 16:23:35 -03:00
scripts perf script python: Add support for sqlite3 to call-graph-from-sql.py 2017-08-15 17:03:38 -03:00
tests perf tests: Fix compile when libunwind's unwind.h is available 2017-09-12 12:34:02 -03:00
trace perf trace beauty: Beautify pkey_{alloc,free,mprotect} arguments 2017-08-28 16:44:47 -03:00
ui perf ui progress: Fix progress update 2017-09-12 12:34:54 -03:00
util perf tools: Open perf.data with O_CLOEXEC flag 2017-09-12 12:34:23 -03:00
.gitignore perf tools: Ignore generated files pmu-events/{jevents,pmu-events.c} for git 2017-03-13 10:59:36 -03:00
Build perf trace: Only build tools/perf/trace/beauty/ when building 'perf trace' 2017-07-18 23:13:52 -03:00
builtin-annotate.c perf annotate browser: Support --show-nr-samples option 2017-08-18 11:15:09 -03:00
builtin-bench.c perf tools: Remove unused 'prefix' from builtin functions 2017-03-27 11:58:09 -03:00
builtin-buildid-cache.c perf buildid-cache: Cache debuginfo 2017-07-18 23:14:11 -03:00
builtin-buildid-list.c perf tools: Include errno.h where needed 2017-04-19 13:01:51 -03:00
builtin-c2c.c perf tools: Replace error() with pr_err() 2017-06-27 11:22:31 -03:00
builtin-config.c perf config: Check not only section->from_system_config but also item's 2017-09-12 12:35:11 -03:00
builtin-data.c perf data: Add doc when no conversion support compiled 2017-07-28 16:30:45 -03:00
builtin-diff.c perf config: Do not die when parsing u64 or int config values 2017-06-27 11:44:58 -03:00
builtin-evlist.c perf tools: Remove unused 'prefix' from builtin functions 2017-03-27 11:58:09 -03:00
builtin-ftrace.c tools include: Adopt strstarts() from the kernel 2017-07-20 15:46:10 -03:00
builtin-help.c tools include: Adopt strstarts() from the kernel 2017-07-20 15:46:10 -03:00
builtin-inject.c perf tools: Add feature header record to pipe-mode 2017-07-18 23:14:36 -03:00
builtin-kallsyms.c perf tools: Including missing inttypes.h header 2017-04-19 13:01:46 -03:00
builtin-kmem.c mm: treewide: remove GFP_TEMPORARY allocation flag 2017-09-13 18:53:16 -07:00
builtin-kvm.c perf tools: Remove poll.h and wait.h from util.h 2017-04-24 13:43:34 -03:00
builtin-list.c perf tools: Remove unused 'prefix' from builtin functions 2017-03-27 11:58:09 -03:00
builtin-lock.c perf tools: Include errno.h where needed 2017-04-19 13:01:51 -03:00
builtin-mem.c perf mem: Support physical address 2017-09-01 14:46:23 -03:00
builtin-probe.c perf buildid-cache: Support binary objects from other namespaces 2017-07-18 23:14:11 -03:00
builtin-record.c perf tools: Support new sample type for physical address 2017-09-01 14:46:00 -03:00
builtin-report.c perf report: Group stat values on global event id 2017-08-28 16:44:44 -03:00
builtin-sched.c perf tools: Replace error() with pr_err() 2017-06-27 11:22:31 -03:00
builtin-script.c perf script: Support physical address 2017-09-01 14:46:29 -03:00
builtin-stat.c perf stat: Wait for the correct child 2017-09-12 12:49:13 -03:00
builtin-timechart.c perf tools: Use just forward declarations for struct thread where possible 2017-04-24 13:43:35 -03:00
builtin-top.c perf top: Support lookup of symbols in other mount namespaces. 2017-07-25 22:43:16 -03:00
builtin-trace.c perf trace: Support syscall name globbing 2017-09-01 14:45:58 -03:00
builtin-version.c perf tools: Remove string.h, unistd.h and sys/stat.h from util.h 2017-04-24 13:43:33 -03:00
builtin.h perf tools: Remove stale prototypes from builtin.h 2017-04-24 13:43:33 -03:00
check-headers.sh tools include uapi: Grab a copy of linux/vhost.h 2017-08-01 13:04:56 -03:00
command-list.txt perf tools: Missing c2c command in command-list 2017-03-13 10:59:31 -03:00
CREDITS
design.txt
Makefile perf build tests: Do parallell builds with 'build-test' 2016-02-04 15:57:00 -03:00
Makefile.config perf tools: Robustify detection of clang binary 2017-08-28 16:44:46 -03:00
Makefile.perf perf trace beauty: Beautify pkey_{alloc,free,mprotect} arguments 2017-08-28 16:44:47 -03:00
MANIFEST tools include uapi: Grab a copy of linux/vhost.h 2017-08-01 13:04:56 -03:00
perf-archive.sh
perf-completion.sh
perf-read-vdso.c
perf-sys.h perf tools: Use default CPUINFO_PROC where it fits 2017-08-17 16:58:21 -03:00
perf-with-kcore.sh
perf.c perf tools: Support running perf binaries with a dash in their name 2017-09-12 12:48:54 -03:00
perf.h perf tools: Support new sample type for physical address 2017-09-01 14:46:00 -03:00