user/sven/linux.git/include/trace/events/compaction.h, branch v4.11.3

mm, trace: extract COMPACTION_STATUS and ZONE_TYPE to a common header

2017-02-23T00:41:27Z

COMPACTION_STATUS resp. ZONE_TYPE are currently used to translate enum compact_result resp. struct zone index into their symbolic names for an easier post processing. The follow up patch would like to reuse this as well. The code involves some preprocessor black magic which is better not duplicated elsewhere so move it to a common mm tracing relate header. Link: http://lkml.kernel.org/r/20161220130135.15719-2-mhocko@kernel.org Signed-off-by: Michal Hocko Acked-by: Vlastimil Babka Cc: David Rientjes Cc: Johannes Weiner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm, compaction: rename COMPACT_PARTIAL to COMPACT_SUCCESS

2016-10-08T01:46:27Z

COMPACT_PARTIAL has historically meant that compaction returned after doing some work without fully compacting a zone. It however didn't distinguish if compaction terminated because it succeeded in creating the requested high-order page. This has changed recently and now we only return COMPACT_PARTIAL when compaction thinks it succeeded, or the high-order watermark check in compaction_suitable() passes and no compaction needs to be done. So at this point we can make the return value clearer by renaming it to COMPACT_SUCCESS. The next patch will remove some redundant tests for success where compaction just returned COMPACT_SUCCESS. Link: http://lkml.kernel.org/r/20160810091226.6709-4-vbabka@suse.cz Signed-off-by: Vlastimil Babka Tested-by: Lorenzo Stoakes Acked-by: Michal Hocko Cc: Mel Gorman Cc: Joonsoo Kim Cc: David Rientjes Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm, compaction: introduce direct compaction priority

2016-07-28T23:07:41Z

In the context of direct compaction, for some types of allocations we would like the compaction to either succeed or definitely fail while trying as hard as possible. Current async/sync_light migration mode is insufficient, as there are heuristics such as caching scanner positions, marking pageblocks as unsuitable or deferring compaction for a zone. At least the final compaction attempt should be able to override these heuristics. To communicate how hard compaction should try, we replace migration mode with a new enum compact_priority and change the relevant function signatures. In compact_zone_order() where struct compact_control is constructed, the priority is mapped to suitable control flags. This patch itself has no functional change, as the current priority levels are mapped back to the same migration modes as before. Expanding them will be done next. Note that !CONFIG_COMPACTION variant of try_to_compact_pages() is removed, as the only caller exists under CONFIG_COMPACTION. Link: http://lkml.kernel.org/r/20160721073614.24395-8-vbabka@suse.cz Signed-off-by: Vlastimil Babka Acked-by: Michal Hocko Acked-by: Mel Gorman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm, compaction: distinguish between full and partial COMPACT_COMPLETE

2016-05-21T00:58:30Z

COMPACT_COMPLETE now means that compaction and free scanner met. This is not very useful information if somebody just wants to use this feedback and make any decisions based on that. The current caller might be a poor guy who just happened to scan tiny portion of the zone and that could be the reason no suitable pages were compacted. Make sure we distinguish the full and partial zone walks. Consumers should treat COMPACT_PARTIAL_SKIPPED as a potential success and be optimistic in retrying. The existing users of COMPACT_COMPLETE are conservatively changed to use COMPACT_PARTIAL_SKIPPED as well but some of them should be probably reconsidered and only defer the compaction only for COMPACT_COMPLETE with the new semantic. This patch shouldn't introduce any functional changes. Signed-off-by: Michal Hocko Acked-by: Vlastimil Babka Acked-by: Hillf Danton Cc: David Rientjes Cc: Johannes Weiner Cc: Joonsoo Kim Cc: Mel Gorman Cc: Tetsuo Handa Cc: Vladimir Davydov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm, compaction: distinguish COMPACT_DEFERRED from COMPACT_SKIPPED

2016-05-21T00:58:30Z

try_to_compact_pages() can currently return COMPACT_SKIPPED even when the compaction is defered for some zone just because zone DMA is skipped in 99% of cases due to watermark checks. This makes COMPACT_DEFERRED basically unusable for the page allocator as a feedback mechanism. Make sure we distinguish those two states properly and switch their ordering in the enum. This would mean that the COMPACT_SKIPPED will be returned only when all eligible zones are skipped. As a result COMPACT_DEFERRED handling for THP in __alloc_pages_slowpath will be more precise and we would bail out rather than reclaim. Signed-off-by: Michal Hocko Acked-by: Vlastimil Babka Acked-by: Hillf Danton Cc: David Rientjes Cc: Johannes Weiner Cc: Joonsoo Kim Cc: Mel Gorman Cc: Tetsuo Handa Cc: Vladimir Davydov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm, compaction: introduce kcompactd

2016-03-17T22:09:34Z

Memory compaction can be currently performed in several contexts: - kswapd balancing a zone after a high-order allocation failure - direct compaction to satisfy a high-order allocation, including THP page fault attemps - khugepaged trying to collapse a hugepage - manually from /proc The purpose of compaction is two-fold. The obvious purpose is to satisfy a (pending or future) high-order allocation, and is easy to evaluate. The other purpose is to keep overal memory fragmentation low and help the anti-fragmentation mechanism. The success wrt the latter purpose is more The current situation wrt the purposes has a few drawbacks: - compaction is invoked only when a high-order page or hugepage is not available (or manually). This might be too late for the purposes of keeping memory fragmentation low. - direct compaction increases latency of allocations. Again, it would be better if compaction was performed asynchronously to keep fragmentation low, before the allocation itself comes. - (a special case of the previous) the cost of compaction during THP page faults can easily offset the benefits of THP. - kswapd compaction appears to be complex, fragile and not working in some scenarios. It could also end up compacting for a high-order allocation request when it should be reclaiming memory for a later order-0 request. To improve the situation, we should be able to benefit from an equivalent of kswapd, but for compaction - i.e. a background thread which responds to fragmentation and the need for high-order allocations (including hugepages) somewhat proactively. One possibility is to extend the responsibilities of kswapd, which could however complicate its design too much. It should be better to let kswapd handle reclaim, as order-0 allocations are often more critical than high-order ones. Another possibility is to extend khugepaged, but this kthread is a single instance and tied to THP configs. This patch goes with the option of a new set of per-node kthreads called kcompactd, and lays the foundations, without introducing any new tunables. The lifecycle mimics kswapd kthreads, including the memory hotplug hooks. For compaction, kcompactd uses the standard compaction_suitable() and ompact_finished() criteria and the deferred compaction functionality. Unlike direct compaction, it uses only sync compaction, as there's no allocation latency to minimize. This patch doesn't yet add a call to wakeup_kcompactd. The kswapd compact/reclaim loop for high-order pages will be replaced by waking up kcompactd in the next patch with the description of what's wrong with the old approach. Waking up of the kcompactd threads is also tied to kswapd activity and follows these rules: - we don't want to affect any fastpaths, so wake up kcompactd only from the slowpath, as it's done for kswapd - if kswapd is doing reclaim, it's more important than compaction, so don't invoke kcompactd until kswapd goes to sleep - the target order used for kswapd is passed to kcompactd Future possible future uses for kcompactd include the ability to wake up kcompactd on demand in special situations, such as when hugepages are not available (currently not done due to __GFP_NO_KSWAPD) or when a fragmentation event (i.e. __rmqueue_fallback()) occurs. It's also possible to perform periodic compaction with kcompactd. [arnd@arndb.de: fix build errors with kcompactd] [paul.gortmaker@windriver.com: don't use modular references for non modular code] Signed-off-by: Vlastimil Babka Cc: Andrea Arcangeli Cc: "Kirill A. Shutemov" Cc: Rik van Riel Cc: Joonsoo Kim Cc: Mel Gorman Cc: David Rientjes Cc: Michal Hocko Cc: Johannes Weiner Signed-off-by: Arnd Bergmann Signed-off-by: Paul Gortmaker Cc: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm, tracing: unify mm flags handling in tracepoints and printk

2016-03-15T23:55:16Z

In tracepoints, it's possible to print gfp flags in a human-friendly format through a macro show_gfp_flags(), which defines a translation array and passes is to __print_flags(). Since the following patch will introduce support for gfp flags printing in printk(), it would be nice to reuse the array. This is not straightforward, since __print_flags() can't simply reference an array defined in a .c file such as mm/debug.c - it has to be a macro to allow the macro magic to communicate the format to userspace tools such as trace-cmd. The solution is to create a macro __def_gfpflag_names which is used both in show_gfp_flags(), and to define the gfpflag_names[] array in mm/debug.c. On the other hand, mm/debug.c also defines translation tables for page flags and vma flags, and desire was expressed (but not implemented in this series) to use these also from tracepoints. Thus, this patch also renames the events/gfpflags.h file to events/mmflags.h and moves the table definitions there, using the same macro approach as for gfpflags. This allows translating all three kinds of mm-specific flags both in tracepoints and printk. Signed-off-by: Vlastimil Babka Reviewed-by: Michal Hocko Cc: Steven Rostedt Cc: Peter Zijlstra Cc: Arnaldo Carvalho de Melo Cc: Ingo Molnar Cc: Rasmus Villemoes Cc: Joonsoo Kim Cc: Minchan Kim Cc: Sasha Levin Cc: "Kirill A. Shutemov" Cc: Mel Gorman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm, compaction: distinguish contended status in tracepoints

2015-11-06T03:34:48Z

Compaction returns prematurely with COMPACT_PARTIAL when contended or has fatal signal pending. This is ok for the callers, but might be misleading in the traces, as the usual reason to return COMPACT_PARTIAL is that we think the allocation should succeed. After this patch we distinguish the premature ending condition in the mm_compaction_finished and mm_compaction_end tracepoints. The contended status covers the following reasons: - lock contention or need_resched() detected in async compaction - fatal signal pending - too many pages isolated in the zone (only for async compaction) Further distinguishing the exact reason seems unnecessary for now. Signed-off-by: Vlastimil Babka Cc: Joonsoo Kim Cc: Mel Gorman Cc: David Rientjes Cc: Steven Rostedt Cc: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm, compaction: export tracepoints zone names to userspace

2015-11-06T03:34:48Z

Some compaction tracepoints use zone->name to print which zone is being compacted. This works for in-kernel printing, but not userspace trace printing of raw captured trace such as via trace-cmd report. This patch uses zone_idx() instead of zone->name as the raw value, and when printing, converts the zone_type to string using the appropriate EM() macros and some ugly tricks to overcome the problem that half the values depend on CONFIG_ options and one does not simply use #ifdef inside of #define. trace-cmd output before: transhuge-stres-4235 [000] 453.149280: mm_compaction_finished: node=0 zone=ffffffff81815d7a order=9 ret=partial after: transhuge-stres-4235 [000] 453.149280: mm_compaction_finished: node=0 zone=Normal order=9 ret=partial Signed-off-by: Vlastimil Babka Reviewed-by: Steven Rostedt Cc: Joonsoo Kim Cc: Ingo Molnar Cc: Mel Gorman Cc: David Rientjes Cc: Valentin Rothberg Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm, compaction: export tracepoints status strings to userspace

2015-11-06T03:34:48Z

Some compaction tracepoints convert the integer return values to strings using the compaction_status_string array. This works for in-kernel printing, but not userspace trace printing of raw captured trace such as via trace-cmd report. This patch converts the private array to appropriate tracepoint macros that result in proper userspace support. trace-cmd output before: transhuge-stres-4235 [000] 453.149280: mm_compaction_finished: node=0 zone=ffffffff81815d7a order=9 ret= after: transhuge-stres-4235 [000] 453.149280: mm_compaction_finished: node=0 zone=ffffffff81815d7a order=9 ret=partial Signed-off-by: Vlastimil Babka Reviewed-by: Steven Rostedt Cc: Joonsoo Kim Cc: Ingo Molnar Cc: Mel Gorman Cc: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds