Hi, On Tue, Nov 3, 2015 at 4:08 PM, Caires Vinicius <[email protected]> wrote:
> 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. > This sounds like your running out of virtual memory. Maybe you're running without swap space? Per. > > > 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> >> > -- *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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