I forgot about your min_free_kbytes question: While I would personally recommend 131072 as *a starting point*, this value does not translate directly to what is actually retained as free RAM. In my experience, the kernel's behavior is non-linear, non-deterministic, and very delicate. Usually the kernel will keep much more free RAM than specified (2-3x), and modifying this value too often under load will cause permanent behavior problems in the kernel.
Setting it to 10% is a terrible idea under any circumstance I can imagine. The goal with this setting in the context of a backing-store cache is to set it high enough that you have 5-15 seconds of read/write I/O throughput available for bursts. For example, if Varnish is committing 5MB/s to/from disk, make sure you have 25-75MB of RAM free at a minimum. This might only translate to a min_free_kbytes of 12000-30000. I'd strongly suggest modifying the value slowly and carefully, ideally only once after a reboot via sysctl.conf. But once done, my 1TB -spersistent Varnish instances became very stable. -- kb On Fri, Apr 8, 2011 at 13:55, Ken Brownfield <[email protected]> wrote: > This means the child process died and restarted (the reason for this should > appear earlier in the log; perhaps your cli_timeout is too low under a > heavily loaded system -- try 20s). > > "-sfile" is not persistent storage, so when the child process restarts it > uses a new, empty storage structure. You should have luck with > "-spersistent" on the latest Varnish or trunk, at least for child process > restarts. > > FWIW, > -- > kb > > > > On Fri, Apr 8, 2011 at 01:55, Jean-Francois Laurens < > [email protected]> wrote: > >> Hi Ken, >> >> Thanks for the hint ! >> You’re affecting here 128Mb, how did you get to this munber ? I read >> somewhere that this value can be set to 10% of the actual memory size which >> would be in my case 800Mb, does it make sense for you ? >> I read aswell that setting this value to high would crash the system >> immediately. >> >> >> Yesterday evening, the system was in heavy load but varnish did not hang ! >> Instead it dropped all its objects ! Then the load went back fine. >> It seems setting –sfile to 40Gb suits better the memory capability for >> this server. >> A question remains though ... Why all the objects were dropped ? >> Attached is a plot from cacti regarding the number of objects. >> >> The only thing I could get form the messages log is this : >> Apr 7 19:00:29 server-01-39 varnishd[3732]: Child (3733) died signal=3 >> Apr 7 19:00:29 server-01-39 varnishd[3732]: Child cleanup complete >> Apr 7 19:00:29 server-01-39 varnishd[3732]: child (29359) Started >> Apr 7 19:00:29 server-01-39 varnishd[3732]: Child (29359) said >> Apr 7 19:00:29 server-01-39 varnishd[3732]: Child (29359) said Child >> starts >> Apr 7 19:00:29 server-01-39 varnishd[3732]: Child (29359) said managed to >> mmap 42949672960 bytes of 42949672960 >> >> >> How could I get to know what is realy happening that could explain this >> behaviour ? >> >> Cheers, >> Jef >> >
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