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d1a291437f
The event structures used by the trace events are mostly persistent, but they are also allocated by kmalloc, which is not the best at allocating space for what is used. By converting these kmallocs into kmem_cache_allocs, we can save over 50K of space that is permanently allocated. After boot we have: slab name active allocated size --------- ------ --------- ---- ftrace_event_file 979 1005 56 67 1 ftrace_event_field 2301 2310 48 77 1 The ftrace_event_file has at boot up 979 active objects out of 1005 allocated in the slabs. Each object is 56 bytes. In a normal kmalloc, that would allocate 64 bytes for each object. 1005 - 979 = 26 objects not used 26 * 56 = 1456 bytes wasted But if we used kmalloc: 64 - 56 = 8 bytes unused per allocation 8 * 979 = 7832 bytes wasted 7832 - 1456 = 6376 bytes in savings Doing the same for ftrace_event_field where there's 2301 objects allocated in a slab that can hold 2310 with 48 bytes each we have: 2310 - 2301 = 9 objects not used 9 * 48 = 432 bytes wasted A kmalloc would also use 64 bytes per object: 64 - 48 = 16 bytes unused per allocation 16 * 2301 = 36816 bytes wasted! 36816 - 432 = 36384 bytes in savings This change gives us a total of 42760 bytes in savings. At least on my machine, but as there's a lot of these persistent objects for all configurations that use trace points, this is a net win. Thanks to Ezequiel Garcia for his trace_analyze presentation which pointed out the wasted space in my code. Cc: Ezequiel Garcia <elezegarcia@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> |
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| .. | ||
| blktrace.c | ||
| ftrace.c | ||
| Kconfig | ||
| Makefile | ||
| power-traces.c | ||
| ring_buffer.c | ||
| ring_buffer_benchmark.c | ||
| rpm-traces.c | ||
| trace.c | ||
| trace.h | ||
| trace_branch.c | ||
| trace_clock.c | ||
| trace_entries.h | ||
| trace_event_perf.c | ||
| trace_events.c | ||
| trace_events_filter.c | ||
| trace_events_filter_test.h | ||
| trace_export.c | ||
| trace_functions.c | ||
| trace_functions_graph.c | ||
| trace_irqsoff.c | ||
| trace_kdb.c | ||
| trace_kprobe.c | ||
| trace_mmiotrace.c | ||
| trace_nop.c | ||
| trace_output.c | ||
| trace_output.h | ||
| trace_printk.c | ||
| trace_probe.c | ||
| trace_probe.h | ||
| trace_sched_switch.c | ||
| trace_sched_wakeup.c | ||
| trace_selftest.c | ||
| trace_selftest_dynamic.c | ||
| trace_stack.c | ||
| trace_stat.c | ||
| trace_stat.h | ||
| trace_syscalls.c | ||
| trace_uprobe.c | ||