Re: [PATCH 00/46] rcu-walk and dcache scaling

[Dave Chinner]

On Sat, Nov 27, 2010 at 09:15:58PM +1100, Nick Piggin wrote:
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/npiggin/linux-npiggin.git vfs-scale-working
> 
> Here is an new set of vfs patches for review, not that there was much interest
> last time they were posted. It is structured like:
> 
> * preparation patches
> * introduce new locks to take over dcache_lock, then remove it
> * cleaning up and reworking things for new locks
> * rcu-walk path walking
> * start on some fine grained locking steps

Stress test doing:

	single thread 50M inode create
	single thread rm -rf
	2-way 50M inode create
	2-way rm -rf
	4-way 50M inode create
	4-way rm -rf
	8-way 50M inode create
	8-way rm -rf
	8-way 250M inode create
	8-way rm -rf

Failed about 5 minutes into the "4-way rm -rf" (~3 hours into the test)
with a CPU stuck spinning on here:

[37372.084012] NMI backtrace for cpu 5
[37372.084012] CPU 5 
[37372.084012] Modules linked in:
[37372.084012] 
[37372.084012] Pid: 15214, comm: rm Not tainted 2.6.37-rc4-dgc+ #797 /Bochs
[37372.084012] RIP: 0010:[<ffffffff810643c4>]  [<ffffffff810643c4>] __ticket_spin_lock+0x14/0x20
[37372.084012] RSP: 0018:ffff880114643c98  EFLAGS: 00000213
[37372.084012] RAX: 0000000000008801 RBX: ffff8800687be6c0 RCX: ffff8800c4eb2688
[37372.084012] RDX: ffff880114643d38 RSI: ffff8800dfd4ea80 RDI: ffff880114643d14
[37372.084012] RBP: ffff880114643c98 R08: 0000000000000003 R09: 0000000000000000
[37372.084012] R10: 0000000000000000 R11: dead000000200200 R12: ffff880114643d14
[37372.084012] R13: ffff880114643cb8 R14: ffff880114643d38 R15: ffff8800687be71c
[37372.084012] FS:  00007fd6d7c93700(0000) GS:ffff8800dfd40000(0000) knlGS:0000000000000000
[37372.084012] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[37372.084012] CR2: 0000000000bbd108 CR3: 0000000107146000 CR4: 00000000000006e0
[37372.084012] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[37372.084012] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[37372.084012] Process rm (pid: 15214, threadinfo ffff880114642000, task ffff88011b16f890)
[37372.084012] Stack:
[37372.084012]  ffff880114643ca8 ffffffff81ad044e ffff880114643cf8 ffffffff81167ae7
[37372.084012]  0000000000000000 ffff880114643d38 000000000000000e ffff88011901d800
[37372.084012]  ffff8800cdb7cf5c ffff88011901d8e0 0000000000000000 0000000000000000
[37372.084012] Call Trace:
[37372.084012]  [<ffffffff81ad044e>] _raw_spin_lock+0xe/0x20
[37372.084012]  [<ffffffff81167ae7>] shrink_dentry_list+0x47/0x370
[37372.084012]  [<ffffffff81167f5e>] __shrink_dcache_sb+0x14e/0x1e0
[37372.084012]  [<ffffffff81168456>] shrink_dcache_parent+0x276/0x2d0
[37372.084012]  [<ffffffff81ad044e>] ? _raw_spin_lock+0xe/0x20
[37372.084012]  [<ffffffff8115daa2>] dentry_unhash+0x42/0x80
[37372.084012]  [<ffffffff8115db48>] vfs_rmdir+0x68/0x100
[37372.084012]  [<ffffffff8115fd93>] do_rmdir+0x113/0x130
[37372.084012]  [<ffffffff8114f5ad>] ? filp_close+0x5d/0x90
[37372.084012]  [<ffffffff8115fde5>] sys_unlinkat+0x35/0x40
[37372.084012]  [<ffffffff8103a002>] system_call_fastpath+0x16/0x1b
[37372.084012] Code: c1 c1 41 06 81 e9 dd fe ff ff 90 90 90 90 90 90 90 90 90 90 90 90 90 55 b8 00 01 00 00 48 89 e5 f0 66 0f c1 07 38 e0 74 06 f3 90 <8a> 07 eb f6 c9 c3 66 0f 1f 44 00 00 55 48 89 e5 0f b7 07 38 e0 
[37372.084012] Call Trace:
[37372.084012]  [<ffffffff81ad044e>] _raw_spin_lock+0xe/0x20
[37372.084012]  [<ffffffff81167ae7>] shrink_dentry_list+0x47/0x370
[37372.084012]  [<ffffffff81167f5e>] __shrink_dcache_sb+0x14e/0x1e0
[37372.084012]  [<ffffffff81168456>] shrink_dcache_parent+0x276/0x2d0
[37372.084012]  [<ffffffff81ad044e>] ? _raw_spin_lock+0xe/0x20
[37372.084012]  [<ffffffff8115daa2>] dentry_unhash+0x42/0x80
[37372.084012]  [<ffffffff8115db48>] vfs_rmdir+0x68/0x100
[37372.084012]  [<ffffffff8115fd93>] do_rmdir+0x113/0x130
[37372.084012]  [<ffffffff8114f5ad>] ? filp_close+0x5d/0x90
[37372.084012]  [<ffffffff8115fde5>] sys_unlinkat+0x35/0x40
[37372.084012]  [<ffffffff8103a002>] system_call_fastpath+0x16/0x1b

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx
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