On 05/19/2015 05:13 PM, Mel Gorman wrote:
On Tue, May 19, 2015 at 04:53:40PM +0200, Michal Hocko wrote:
On Tue 19-05-15 10:18:07, Johannes Weiner wrote:
CC'ing Tejun and cgroups for the generic cgroup interface part
On Tue, May 19, 2015 at 11:40:57AM +0100, Mel Gorman wrote:
[...]
/usr/src/linux-4.0-vanilla/mm/memcontrol.c 6.6441 395842
mem_cgroup_try_charge 2.950% 175781
Ouch. Do you have a way to get the per-instruction breakdown of this?
This function really isn't doing much. I'll try to reproduce it here
too, I haven't seen such high costs with pft in the past.
try_charge 0.150% 8928
get_mem_cgroup_from_mm 0.121% 7184
Indeed! try_charge + get_mem_cgroup_from_mm which I would expect to be
the biggest consumers here are below 10% of the mem_cgroup_try_charge.
Other than that the function doesn't do much else than some flags
queries and css_put...
Do you have the full trace? Sorry for a stupid question but do inlines
from other header files get accounted to memcontrol.c?
The annotations for those functions look like with some very basic notes are
as follows. Note that I've done almost no research on this. I just noticed
that the memcg overhead was still there when looking for something else.
ffffffff811c15f0 <mem_cgroup_try_charge>: /* mem_cgroup_try_charge total: 176903 2.9692 */
765 0.0128 :ffffffff811c15f0: callq ffffffff816435e0 <__fentry__>
78 0.0013 :ffffffff811c15f5: push %rbp
1185 0.0199 :ffffffff811c15f6: mov %rsp,%rbp
356 0.0060 :ffffffff811c15f9: push %r14
209 0.0035 :ffffffff811c15fb: push %r13
1599 0.0268 :ffffffff811c15fd: push %r12
320 0.0054 :ffffffff811c15ff: mov %rcx,%r12
305 0.0051 :ffffffff811c1602: push %rbx
325 0.0055 :ffffffff811c1603: sub $0x10,%rsp
878 0.0147 :ffffffff811c1607: mov 0xb7501b(%rip),%ecx # ffffffff81d36628 <memory_cgrp_subsys+0x68>
571 0.0096 :ffffffff811c160d: test %ecx,%ecx
### MEL: Function entry, check for mem_cgroup_disabled()
:ffffffff811c160f: je ffffffff811c1630 <mem_cgroup_try_charge+0x40>
:ffffffff811c1611: xor %eax,%eax
:ffffffff811c1613: xor %ebx,%ebx
1 1.7e-05 :ffffffff811c1615: mov %rbx,(%r12)
7 1.2e-04 :ffffffff811c1619: add $0x10,%rsp
1211 0.0203 :ffffffff811c161d: pop %rbx
5 8.4e-05 :ffffffff811c161e: pop %r12
5 8.4e-05 :ffffffff811c1620: pop %r13
1249 0.0210 :ffffffff811c1622: pop %r14
7 1.2e-04 :ffffffff811c1624: pop %rbp
5 8.4e-05 :ffffffff811c1625: retq
:ffffffff811c1626: nopw %cs:0x0(%rax,%rax,1)
295 0.0050 :ffffffff811c1630: mov (%rdi),%rax
160703 2.6973 :ffffffff811c1633: mov %edx,%r13d
#### MEL: I was surprised to see this atrocity. It's a PageSwapCache check
Looks like sampling is off by instruction, because why would a reg->reg
mov took so long. So it's probably a cache miss on struct page, pointer
to which is in rdi. Which is weird, I would expect memcg to be called on
struct pages that are already hot. It would also mean that if you don't
fetch the struct page from the memcg code, then the following code in
the caller will most likely work on the struct page and get the cache
miss anyway?
#### /usr/src/linux-4.0-vanilla/./arch/x86/include/asm/bitops.h:311
#### /usr/src/linux-4.0-vanilla/include/linux/page-flags.h:261
#### /usr/src/linux-4.0-vanilla/mm/memcontrol.c:5473
####
#### Everything after here is consistent small amounts of overhead just from
#### being called a lot
179 0.0030 :ffffffff811c1636: test $0x10000,%eax
:ffffffff811c163b: je ffffffff811c1648 <mem_cgroup_try_charge+0x58>
:ffffffff811c163d: xor %eax,%eax
:ffffffff811c163f: xor %ebx,%ebx
:ffffffff811c1641: cmpq $0x0,0x38(%rdi)
:ffffffff811c1646: jne ffffffff811c1615 <mem_cgroup_try_charge+0x25>
1343 0.0225 :ffffffff811c1648: mov (%rdi),%rax
26 4.4e-04 :ffffffff811c164b: mov $0x1,%r14d
24 4.0e-04 :ffffffff811c1651: test $0x40,%ah
:ffffffff811c1654: je ffffffff811c1665 <mem_cgroup_try_charge+0x75>
:ffffffff811c1656: mov (%rdi),%rax
:ffffffff811c1659: test $0x40,%ah
:ffffffff811c165c: je ffffffff811c1665 <mem_cgroup_try_charge+0x75>
:ffffffff811c165e: mov 0x68(%rdi),%rcx
:ffffffff811c1662: shl %cl,%r14d
1225 0.0206 :ffffffff811c1665: mov 0xb74f35(%rip),%eax # ffffffff81d365a0 <do_swap_account>
66 0.0011 :ffffffff811c166b: test %eax,%eax
:ffffffff811c166d: jne ffffffff811c16a8 <mem_cgroup_try_charge+0xb8>
3 5.0e-05 :ffffffff811c166f: mov %rsi,%rdi
22 3.7e-04 :ffffffff811c1672: callq ffffffff811bc920 <get_mem_cgroup_from_mm>
1291 0.0217 :ffffffff811c1677: mov %rax,%rbx
3 5.0e-05 :ffffffff811c167a: mov %r14d,%edx
:ffffffff811c167d: mov %r13d,%esi
10 1.7e-04 :ffffffff811c1680: mov %rbx,%rdi
1380 0.0232 :ffffffff811c1683: callq ffffffff811c0950 <try_charge>
10 1.7e-04 :ffffffff811c1688: testb $0x1,0x74(%rbx)
1235 0.0207 :ffffffff811c168c: je ffffffff811c16d0 <mem_cgroup_try_charge+0xe0>
7 1.2e-04 :ffffffff811c168e: cmp $0xfffffffc,%eax
:ffffffff811c1691: jne ffffffff811c1615 <mem_cgroup_try_charge+0x25>
:ffffffff811c1693: mov 0xb74f0e(%rip),%rbx # ffffffff81d365a8 <root_mem_cgroup>
:ffffffff811c169a: xor %eax,%eax
:ffffffff811c169c: jmpq ffffffff811c1615 <mem_cgroup_try_charge+0x25>
:ffffffff811c16a1: nopl 0x0(%rax)
:ffffffff811c16a8: mov (%rdi),%rax
:ffffffff811c16ab: test $0x10000,%eax
:ffffffff811c16b0: je ffffffff811c166f <mem_cgroup_try_charge+0x7f>
:ffffffff811c16b2: mov %rsi,-0x28(%rbp)
:ffffffff811c16b6: callq ffffffff811c0450 <try_get_mem_cgroup_from_page>
:ffffffff811c16bb: test %rax,%rax
:ffffffff811c16be: mov %rax,%rbx
:ffffffff811c16c1: mov -0x28(%rbp),%rsi
:ffffffff811c16c5: jne ffffffff811c167a <mem_cgroup_try_charge+0x8a>
:ffffffff811c16c7: jmp ffffffff811c166f <mem_cgroup_try_charge+0x7f>
:ffffffff811c16c9: nopl 0x0(%rax)
:ffffffff811c16d0: mov 0x18(%rbx),%rdx
:ffffffff811c16d4: test $0x3,%dl
:ffffffff811c16d7: jne ffffffff811c16df <mem_cgroup_try_charge+0xef>
:ffffffff811c16d9: decq %gs:(%rdx)
:ffffffff811c16dd: jmp ffffffff811c168e <mem_cgroup_try_charge+0x9e>
:ffffffff811c16df: lea 0x10(%rbx),%rdi
:ffffffff811c16e3: lock subq $0x1,0x10(%rbx)
:ffffffff811c16e9: je ffffffff811c16ed <mem_cgroup_try_charge+0xfd>
:ffffffff811c16eb: jmp ffffffff811c168e <mem_cgroup_try_charge+0x9e>
:ffffffff811c16ed: mov %eax,-0x28(%rbp)
:ffffffff811c16f0: callq *0x20(%rbx)
:ffffffff811c16f3: mov -0x28(%rbp),%eax
:ffffffff811c16f6: jmp ffffffff811c168e <mem_cgroup_try_charge+0x9e>
:ffffffff811c16f8: nopl 0x0(%rax,%rax,1)
ffffffff811bc920 <get_mem_cgroup_from_mm>: /* get_mem_cgroup_from_mm total: 7251 0.1217 */
#### MEL: Nothing really big jumped out there at me.
1318 0.0221 :ffffffff811bc920: callq ffffffff816435e0 <__fentry__>
19 3.2e-04 :ffffffff811bc925: push %rbp
42 7.0e-04 :ffffffff811bc926: mov %rsp,%rbp
1278 0.0215 :ffffffff811bc929: jmp ffffffff811bc94b <get_mem_cgroup_from_mm+0x2b>
:ffffffff811bc92b: nopl 0x0(%rax,%rax,1)
1259 0.0211 :ffffffff811bc930: testb $0x1,0x74(%rdx)
161 0.0027 :ffffffff811bc934: jne ffffffff811bc980 <get_mem_cgroup_from_mm+0x60>
:ffffffff811bc936: mov 0x18(%rdx),%rax
:ffffffff811bc93a: test $0x3,%al
:ffffffff811bc93c: jne ffffffff811bc985 <get_mem_cgroup_from_mm+0x65>
:ffffffff811bc93e: incq %gs:(%rax)
:ffffffff811bc942: mov $0x1,%eax
:ffffffff811bc947: test %al,%al
:ffffffff811bc949: jne ffffffff811bc980 <get_mem_cgroup_from_mm+0x60>
13 2.2e-04 :ffffffff811bc94b: test %rdi,%rdi
:ffffffff811bc94e: je ffffffff811bc96c <get_mem_cgroup_from_mm+0x4c>
47 7.9e-04 :ffffffff811bc950: mov 0x340(%rdi),%rax
1410 0.0237 :ffffffff811bc957: test %rax,%rax
:ffffffff811bc95a: je ffffffff811bc96c <get_mem_cgroup_from_mm+0x4c>
26 4.4e-04 :ffffffff811bc95c: mov 0xca0(%rax),%rax
179 0.0030 :ffffffff811bc963: mov 0x70(%rax),%rdx
174 0.0029 :ffffffff811bc967: test %rdx,%rdx
:ffffffff811bc96a: jne ffffffff811bc930 <get_mem_cgroup_from_mm+0x10>
:ffffffff811bc96c: mov 0xb79c35(%rip),%rdx # ffffffff81d365a8 <root_mem_cgroup>
1 1.7e-05 :ffffffff811bc973: testb $0x1,0x74(%rdx)
:ffffffff811bc977: je ffffffff811bc936 <get_mem_cgroup_from_mm+0x16>
:ffffffff811bc979: nopl 0x0(%rax)
1299 0.0218 :ffffffff811bc980: mov %rdx,%rax
4 6.7e-05 :ffffffff811bc983: pop %rbp
21 3.5e-04 :ffffffff811bc984: retq
:ffffffff811bc985: testb $0x2,0x18(%rdx)
:ffffffff811bc989: jne ffffffff811bc9d2 <get_mem_cgroup_from_mm+0xb2>
:ffffffff811bc98b: mov 0x10(%rdx),%rcx
:ffffffff811bc98f: test %rcx,%rcx
:ffffffff811bc992: je ffffffff811bc9d2 <get_mem_cgroup_from_mm+0xb2>
:ffffffff811bc994: lea 0x1(%rcx),%rsi
:ffffffff811bc998: lea 0x10(%rdx),%r8
:ffffffff811bc99c: mov %rcx,%rax
:ffffffff811bc99f: lock cmpxchg %rsi,0x10(%rdx)
:ffffffff811bc9a5: cmp %rcx,%rax
:ffffffff811bc9a8: mov %rax,%rsi
:ffffffff811bc9ab: jne ffffffff811bc9b4 <get_mem_cgroup_from_mm+0x94>
:ffffffff811bc9ad: mov $0x1,%eax
:ffffffff811bc9b2: jmp ffffffff811bc947 <get_mem_cgroup_from_mm+0x27>
:ffffffff811bc9b4: test %rsi,%rsi
:ffffffff811bc9b7: je ffffffff811bc9d2 <get_mem_cgroup_from_mm+0xb2>
:ffffffff811bc9b9: lea 0x1(%rsi),%rcx
:ffffffff811bc9bd: mov %rsi,%rax
:ffffffff811bc9c0: lock cmpxchg %rcx,(%r8)
:ffffffff811bc9c5: cmp %rax,%rsi
:ffffffff811bc9c8: je ffffffff811bc9ad <get_mem_cgroup_from_mm+0x8d>
:ffffffff811bc9ca: mov %rax,%rsi
:ffffffff811bc9cd: test %rsi,%rsi
:ffffffff811bc9d0: jne ffffffff811bc9b9 <get_mem_cgroup_from_mm+0x99>
:ffffffff811bc9d2: xor %eax,%eax
:ffffffff811bc9d4: jmpq ffffffff811bc947 <get_mem_cgroup_from_mm+0x27>
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