On Sun, May 24, 2020 at 8:12 AM Geoff Simmons <[email protected]> wrote: > > On 5/24/20 01:29, [email protected] wrote: > > This notes > > > > https://varnish-cache.org/docs/trunk/installation/platformnotes.html > > > > has a comment about "Transparent hugepages". > > > > Does this still apply to EL8? > > That's a good heads-up that those docs need to be updated -- they refer > to RHEL6 and Linux kernel 3.2. If I'm not mistaken, enabling THP by > default was fairly new at the time, but it's still the default and > that's old news now, as your settings confirmed (just checked that it's > also the default on my Debian stretch laptop). > > The issue is not really the distro or kernel version, but the use of the > THP feature, and it's still a problem, probably always will be. AFAICT > THP does nothing good for Varnish. It's harmless if you're lucky, but it > can be very disruptive. > > I haven't tried it with RHEL8. The doc says that it "is known to cause > sporadic crashes of Varnish", but while I haven't seen crashes, on RHEL7 > I've seen that the memory usage of the cache process bloats up > enormously, orders of magnitude larger than the actual size of the cache > and anything else in Varnish that occupies memory. After disabling THP > for Varnish (as detailed below), I saw memory usage become much smaller, > more like what you'd expect from the cache size and other overhead. > > There's an explanation for why THP causes that, but suffice it to say > that THP creates trouble for a variety of apps that manage a lot of > memory. MongoDB, Oracle, redis and many other projects advise you to > turn it off. THP is inevitably a problem for the jemalloc memory > allocator, which is invariably used with Varnish.
I just wanted to react to the "invariably" word here. This is not accurate, it should read "by default" instead. See ./configure --help: > --with-jemalloc use jemalloc memory allocator. Default is yes on Linux, no > elsewhere And considering that jemalloc is not available in el8, but epel8 instead. I suspect Red Hat ships a varnish package that uses glibc with no custom allocator. Cheers, Dridi _______________________________________________ varnish-misc mailing list [email protected] https://www.varnish-cache.org/lists/mailman/listinfo/varnish-misc
