Quoting Matthew Wilcox (2019-03-07 15:30:51) > Transparent Huge Pages are currently stored in i_pages as pointers to > consecutive subpages. This patch changes that to storing consecutive > pointers to the head page in preparation for storing huge pages more > efficiently in i_pages. > > Large parts of this are "inspired" by Kirill's patch > https://lore.kernel.org/lkml/20170126115819.58875-2-kirill.shutemov@xxxxxxxxxxxxxxx/ > > Signed-off-by: Matthew Wilcox <willy@xxxxxxxxxxxxx> > Acked-by: Jan Kara <jack@xxxxxxx> > Reviewed-by: Kirill Shutemov <kirill@xxxxxxxxxxxxx> > Reviewed-and-tested-by: Song Liu <songliubraving@xxxxxx> > Tested-by: William Kucharski <william.kucharski@xxxxxxxxxx> > Reviewed-by: William Kucharski <william.kucharski@xxxxxxxxxx> I've bisected some new softlockups under THP mempressure to this patch. They are all rcu stalls that look similar to: [ 242.645276] rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: [ 242.645293] rcu: Tasks blocked on level-0 rcu_node (CPUs 0-3): P828 [ 242.645301] (detected by 1, t=5252 jiffies, g=55501, q=221) [ 242.645307] gem_syslatency R running task 0 828 815 0x00004000 [ 242.645315] Call Trace: [ 242.645326] ? __schedule+0x1a0/0x440 [ 242.645332] ? preempt_schedule_irq+0x27/0x50 [ 242.645337] ? apic_timer_interrupt+0xa/0x20 [ 242.645342] ? xas_load+0x3c/0x80 [ 242.645347] ? xas_load+0x8/0x80 [ 242.645353] ? find_get_entry+0x4f/0x130 [ 242.645358] ? pagecache_get_page+0x2b/0x210 [ 242.645364] ? lookup_swap_cache+0x42/0x100 [ 242.645371] ? do_swap_page+0x6f/0x600 [ 242.645375] ? unmap_region+0xc2/0xe0 [ 242.645380] ? __handle_mm_fault+0x7a9/0xfa0 [ 242.645385] ? handle_mm_fault+0xc2/0x1c0 [ 242.645393] ? __do_page_fault+0x198/0x410 [ 242.645399] ? page_fault+0x5/0x20 [ 242.645404] ? page_fault+0x1b/0x20 Any suggestions as to what information you might want? -Chris
