We had some problems with malloc with the same kind of aws instance and the -s malloc,5.8G(80% of the memory total). The only trace of the error was a cannot fork cannot allocate memory into syslog. We're probably missing some point, maybe the instance size ins't the right fit for us.
On Tue, Nov 3, 2015 at 10:56 AM Per Buer <[email protected]> wrote: > Hi, > > > On Tue, Nov 3, 2015 at 1:42 PM, Caires Vinicius <[email protected]> > wrote: > >> We've started to use Varnish 4 with Amazon Linux with EBS SSD of 40GB, >> memory of 7.5GB. We use the file storage with 20G allocated with ttl of 11 >> minutes and grace of 5 hours, all the other configs are standard. >> > I would, on a general basis, recommend against using the file backend. It > will start to struggle with fragmentation relatively quickly and the > performance isn't all that great (lots of unnecessary synchronous reads). > >> Sometimes when we have a lot of request that result into cache miss we >> started to notice that our request latency grows and the iowait stays at >> 100%, something similar to this >> https://www.varnish-cache.org/lists/pipermail/varnish-misc/2008-April/01... >> <https://www.varnish-cache.org/lists/pipermail/varnish-misc/2008-April/016139.html>. >> And our threads reaches the maximum (1000). >> >> Do you guys have any idea why is that? >> > Yeah. New objects get assign a piece of memory, starts writing, triggers > pagefault, kernel takes over and reads/merges the underlying page, varnish > then overwrites that page which then gets written back to disk. This > naturally slows down delivery so Varnish spawns new threads. > > Try malloc. You should start with -s malloc,30G or there about - if you > have lots of small objects you might need to go a bit down to avoid > swapping. > > Not related: You should also move /var/lib/varnish onto tempfs. Linux will > do a lot of writing if the shared memory segment is visible on a filesystem > that is backed by a disk. > -- > *Per Buer* > CTO | Varnish Software AS > Cell: +47 95839117 > We Make Websites Fly! > www.varnish-software.com > <http://info.varnish-software.com/signature> >
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