Re: Large stack usage in fs code (especially for PPC64)

Benjamin Herrenschmidt
2008-11-17T23:05:28Z

On Mon, 2008-11-17 at 15:59 -0500, Steven Rostedt wrote:
> On Mon, 17 Nov 2008, Steven Rostedt wrote:
> >
> > Note, I was using a default config that had CONFIG_IRQSTACKS off and
> > CONFIG_PPC_64K_PAGES on.
>
> Here's my stack after boot up with CONFIG_IRQSTACKS set. Seems that
> softirqs still use the same stack as the process.

No, they should use their own, unless somebody change the softirq code
in ways that break us... (or unless I missed something, we based our
implementation roughtly on what x86 did back then).

Ben.

> root@electra ~> cat /debug/tracing/stack_trace
> Depth Size Location (59 entries)
> ----- ---- --------
> 0) 12384 192 ftrace_call+0x4/0x14
> 1) 12192 128 .sched_clock+0x20/0x60
> 2) 12064 128 .sched_clock_cpu+0x34/0x50
> 3) 11936 144 .cpu_clock+0x3c/0xa0
> 4) 11792 144 .get_timestamp+0x2c/0x50
> 5) 11648 144 .__touch_softlockup_watchdog+0x3c/0x60
> 6) 11504 192 .softlockup_tick+0xe4/0x220
> 7) 11312 128 .run_local_timers+0x34/0x50
> 8) 11184 160 .update_process_times+0x44/0xb0
> 9) 11024 176 .tick_sched_timer+0x8c/0x120
> 10) 10848 160 .__run_hrtimer+0xd8/0x130
> 11) 10688 240 .hrtimer_interrupt+0x16c/0x220
> 12) 10448 160 .timer_interrupt+0xcc/0x110
> 13) 10288 96 decrementer_common+0xe0/0x100
> 14) 10192 784 .ftrace_test_stop_func+0x4c/0x70
> 15) 9408 112 ftrace_call+0x4/0x14
> 16) 9296 144 .init_buffer_head+0x20/0x60
> 17) 9152 256 .cache_alloc_refill+0x5a0/0x740
> 18) 8896 160 .kmem_cache_alloc+0xfc/0x140
> 19) 8736 144 .alloc_buffer_head+0x3c/0xc0
> 20) 8592 176 .alloc_page_buffers+0xb0/0x130
> 21) 8416 160 .create_empty_buffers+0x44/0x1a0
> 22) 8256 1280 .block_read_full_page+0x3b0/0x430
> 23) 6976 144 .blkdev_readpage+0x38/0x60
> 24) 6832 176 .read_cache_page_async+0x124/0x230
> 25) 6656 160 .read_cache_page+0x50/0xe0
> 26) 6496 160 .read_dev_sector+0x58/0x100
> 27) 6336 272 .msdos_partition+0xa4/0x880
> 28) 6064 240 .rescan_partitions+0x1f0/0x430
> 29) 5824 208 .__blkdev_get+0x124/0x3d0
> 30) 5616 144 .blkdev_get+0x3c/0x60
> 31) 5472 192 .register_disk+0x194/0x1f0
> 32) 5280 160 .add_disk+0xe8/0x160
> 33) 5120 224 .sd_probe+0x2f0/0x440
> 34) 4896 176 .driver_probe_device+0x14c/0x380
> 35) 4720 144 .__device_attach+0x38/0x60
> 36) 4576 192 .bus_for_each_drv+0xb8/0x120
> 37) 4384 160 .device_attach+0x94/0xe0
> 38) 4224 144 .bus_attach_device+0x78/0xb0
> 39) 4080 240 .device_add+0x54c/0x730
> 40) 3840 160 .scsi_sysfs_add_sdev+0x7c/0x2e0
> 41) 3680 336 .scsi_probe_and_add_lun+0xb7c/0xc60
> 42) 3344 192 .__scsi_add_device+0x11c/0x150
> 43) 3152 176 .ata_scsi_scan_host+0x238/0x330
> 44) 2976 208 .ata_host_register+0x320/0x3c0
> 45) 2768 192 .ata_host_activate+0xf8/0x190
> 46) 2576 224 .mv_pci_init_one+0x284/0x430
> 47) 2352 160 .pci_device_probe+0x98/0xf0
> 48) 2192 176 .driver_probe_device+0x14c/0x380
> 49) 2016 160 .__driver_attach+0xd4/0x110
> 50) 1856 192 .bus_for_each_dev+0xa8/0x100
> 51) 1664 144 .driver_attach+0x40/0x60
> 52) 1520 192 .bus_add_driver+0x268/0x340
> 53) 1328 176 .driver_register+0x88/0x1d0
> 54) 1152 176 .__pci_register_driver+0x90/0x100
> 55) 976 144 .mv_init+0x38/0xa0
> 56) 832 544 .do_one_initcall+0x78/0x240
> 57) 288 192 .kernel_init+0x21c/0x2b0
> 58) 96 96 .kernel_thread+0x54/0x70
>
> This is still 12K. Kind of big even for a 16K stack.
>
> -- Steve