crucially

sudo mtr -r -w -c 10000 -i 0.01 www.fastly.com
HOST: ubuntu                                   Loss%   Snt   Last   Avg  Best  Wrst StDev
  1.|-- 172.16.1.1                                0.2% 10000    1.0   0.7   0.6 176.0  10.2
  2.|-- 10.0.8.97                                 0.2% 10000    1.0   0.9   0.9 174.9  10.1
  3.|-- 10.0.13.193                              33.5% 10000   98.4  98.7   1.9 687.2 100.0
  4.|-- 66.80.208.web-pass.com                    0.9% 10000    2.1   1.3   1.0 172.7  10.5
  5.|-- 10.0.10.92                                0.8% 10000    2.8   2.2   1.9 169.1   9.8
  6.|-- 173.247.205.38                            0.9% 10000    4.3   3.4   3.1 181.9  10.3
  7.|-- 2-3.365.core.sfo.web-pass.com             1.0% 10000    7.3   3.1   2.7 181.0  10.2
  8.|-- 10.0.7.174                                1.1% 10000    8.0   3.5   3.0 180.0  11.2

crucially

--- a/varnish-cache/bin/varnishd/cache_acceptor.c
+++ b/varnish-cache/bin/varnishd/cache_acceptor.c
@@ -370,6 +370,7 @@
 vca_return_session(struct sess *sp)
 {
 
+	int written = 0;
 	CHECK_OBJ_NOTNULL(sp, SESS_MAGIC);
 	AZ(sp->obj);
 	AZ(sp->vcl);

crucially

--- a/varnish-cache/bin/varnishd/cache_backend.c
+++ b/varnish-cache/bin/varnishd/cache_backend.c
@@ -266,7 +266,7 @@ vbe_Healthy(double now, uintptr_t target, struct backend *backend)
                threshold = backend->saintmode_threshold;
 
        /* Saintmode is disabled */
-       if (threshold == 0)
+       if (threshold == 0 || VTAILQ_EMPTY(&backend->troublelist))
                return (1);
 

crucially

03:23:53 AM  pgpgin/s pgpgout/s   fault/s  majflt/s  pgfree/s pgscank/s pgscand/s pgsteal/s    %vmeff
03:24:08 AM    105.60 631865.60 123521.60      4.00 563194.60 120226.20      0.00  91333.00     75.97
03:24:13 AM   3296.80 621214.40  83720.80    145.00 391110.20 131105.20      0.00 101768.40     77.62
03:24:18 AM   2291.20 610795.20 106200.20    124.20 484164.00 164654.60      0.00 128087.40     77.79

crucially

sub vcl_recv {
#FASTLY recv
 if(req.url ~ "^/dashboard") {
 return(pass);
 }
}

crucially

Device:         rrqm/s   wrqm/s     r/s     w/s    rMB/s    wMB/s avgrq-sz avgqu-sz   await  svctm  %util
sdb               2.03     5.00 1797.60  484.32     8.03     3.95    10.75     2.20    0.96   0.23  52.51
sdc               2.03     5.05 1794.07  483.27     8.01     3.94    10.75     2.64    1.16   0.22  51.05
sdd               1.99     4.95 1798.34  483.41     8.03     3.95    10.75     2.89    1.27   0.22  51.21

crucially

ip r | cut -f 2 -d '/' | cut -d ' ' -f 1  | grep -v "10." | sort | uniq -c  | sort -rn
 196351 24
  36878 22
  34909 23
  27570 21
  27355 20
  19844 19
  11977 16
   9947 18
   5989 17

crucially

arenas[94]:
assigned threads: 30
dirty pages: 24154:58 active:dirty, 0 sweeps, 0 madvises, 0 purged
            allocated      nmalloc      ndalloc    nrequests
small:       46928896      1403902       990678      7990903
large:       28794880         1194          937         7496
total:       75723776      1405096       991615      7998399
active:      98934784
mapped:     104857600
bins:     bin    size regs pgs    allocated      nmalloc      ndalloc    nrequests       nfills     nflushes      newruns       reruns      maxruns      curruns

crucially

174932 61810565 5000 sys_epoll_wait system_call_fastpath
45738 38676481 5000 poll_schedule_timeout do_sys_poll sys_poll system_call_fastpath
74413 86893436 5000 futex_wait_queue_me futex_wait do_futex sys_futex system_call_fastpath
17088 15362918 5000 sk_wait_data tcp_recvmsg inet_recvmsg sock_aio_read do_sync_read vfs_read sys_read system_call_fastpath
20779 1899021 1737 __lock_sock lock_sock_nested inet_csk_accept inet_accept sys_accept4 system_call_fastpath
3194 4171622 4993 poll_schedule_timeout do_select core_sys_select sys_select system_call_fastpath
27287 5619317 12223 sync_page wait_on_page_bit __lock_page_or_retry filemap_fault __do_fault handle_pte_fault handle_mm_fault do_page_fault page_fault tcp_sendmsg inet_sendmsg sock_aio_write
5493 1316064 9971 sync_page wait_on_page_bit __lock_page_or_retry filemap_fault __do_fault handle_pte_fault handle_mm_fault do_page_fault page_fault
358 782 29
60 143479 4832 sk_stream_wait_memory tcp_sendmsg inet_sendmsg sock_aio_write do_sync_readv_writev do_readv_wri

crucially

Linux 2.6.39-fastly-nofsync-forward (varnish-s1) 	09/21/2011 	_x86_64_	(16 CPU)

02:37:07 AM  pgpgin/s pgpgout/s   fault/s  majflt/s  pgfree/s pgscank/s pgscand/s pgsteal/s    %vmeff
02:37:08 AM  29016.00  15336.00  27987.00   6869.00  21111.00 981579.00      0.00   6818.00      0.69
02:37:09 AM  27886.27  41749.02  30091.18   6636.27  20401.96 718294.12      0.00   6944.12      0.97
02:37:10 AM  28925.49  22847.06  23767.65   6596.08  20200.98 798052.94      0.00   7174.51      0.90
02:37:11 AM  32388.00   7668.00  34960.00   7714.00  23989.00 854292.00      0.00   7967.00      0.93
02:37:12 AM  29996.04   8427.72  33377.23   7167.33  21184.16 1039053.47      0.00   7396.04      0.71
02:37:13 AM  33261.22  10032.65  35261.22   7809.18  62774.49 913227.55      0.00  48034.69      5.26
02:37:14 AM  24188.00   3004.00  22451.00   5872.00  26824.00 1041068.00      0.00   4072.00      0.39